Jörgs R80GS Page

Bash plate

A really useful accessory is the larger bash plate. This is a genuine BMW part that was originally designed for the "Paris-Dakar" kits. It is much larger and thicker than the original part (for a direct comparison, see the picture) and protects the complete underside of the engine, including downpipes, intermediate muffler and centerstand. In addition, the smooth surface (no holes) allows the bike to "slide" over rocks if the plate hits them. I found it particularly useful in regions with harsh or rocky roads; after the 2008 spring trip to Tunisia, particularly the rear plate had a number of deep scratches that would certainly have damaged the centerstand and exhaust collector box.

The improved protection has a small downside: Due to the higher weight, you may want to use stronger springs for the centerstand (or simply install additional, "crossed" springs). Another point is that the bash plate installation complicates oil change: Any oil spilled during oil filter removal will be spread by the front bash plate ... and oil coming from the drain plug will hit exactly the top of the centerstand's skid plate, thus being guided in two different places :-( Thus, I prefer draining the oil with the bike on the sidestand and for changing the oil filter I remove the bash plate completely.

Tire combinations

Originally, the GS was equipped with Metzeler Enduro 3, which is a tire that has been developed specifically for the BMW GS series. Indeed it is "the" perfect tire for this bike, with wonderful grip on dry and wet roads as well as off-road, but wear is considerable: The Enduro 3 lasts about 6...9 Mm on the rear wheel, about 12 Mm on the front wheel. Usual tire pressure: 2.2/2.5 bar (front/rear) solo, up to 2.4/2.9 bar fully loaded on street.

In search for a longer-lasting alternative I have tried the Michelin T65 for a while - a few thousand km - on the rear wheel. On dry roads it is a good tire, but as soon as it gets wet it is so slippery that I can only classify this tire as "dangerous". Fortunately it is no longer available.

Between 1992 and 1995 I rode my GS with street tires. The big advantage was that the bike rolled notably more smooth, and I got the impression that handling was also a bit better. The Metzeler ME33 was one of the few street tires that were available in 21" sizes. A good tire with good grip, but as soon as it was a bit "used" the tire became somewhat slippery in the corners - I had to change the tire after about 12 Mm. On the rear wheel, the Metzeler ME55 was a perfect street tire for this bike. No problems on any kind of road, excellent grip, lifetime 7.5...9.5 Mm.

The Metzeler Enduro 4 Radial was a radi(c)ally different tire - much more road-oriented, with large amounts of positive profile. Lifetime was about twice that of the Enduro 3, with reasonable handling on dry terrain. In the Radial version (only available for the rear wheel), the properties were identical to that of the Enduro 4, but lifetime was considerably higher: I got between 11 and 14 Mm from a rear tire. Usual tire pressures were identical to the Enduro 3 above; for long trips on gravel roads, I reduced tire pressure down to 1.8/2.0 bar or less - the bike was much better to handle on loose ground. - For the front wheel, Metzeler has changed the profile of the Enduro 4 a few times. The earlier versions developed a "sawtooth" profile that made tire changes necessary after 8...10 Mm. The more recent versions easily lasted for more than 10 Mm.

In late 2003, I changed for quite a while to Mitas E-08 for the "usual" riding. They have a much "rounder" profile than the Metzeler, which leads to a surprising improvement in handling. This tire is among the best I ever experienced on this motorcycle; both on dry and wet roads they are excellent. In particular the front tire has surprising properties: Even when it has already developed a sawtooth profile, it still sticks very well to the road and braking behaviour has clearly improved. In addition, its rather "open" profile allows for very relaxed riding even in deep gravel, where a Metzeler Enduro 4 would simply fail to guide the front wheel. Tire pressures are as mentioned above; with reduced pressure (1.8 and 2.0 bar, respectively) even long passages on harsh gravel are possible without problems. - The rear tire lasts about 7 Mm, the one on the front wheel about 10 Mm. The only downside is that, for some reason that escapes me, the tubeless versions are more and more difficult to obtain. In addition, the price for the E-08 has almost doubled in five years, so I switched to the Heidenau K60 (see below).

Another tire from the same manufacturer is the Mitas E-07, which I used on the rear wheel (in combination with E-08 front). The relatively open profile yields good traction on loose ground; overall handling and properties on tarmac are comparable to that of the E-08. A disadvantage is that the tire is very noisy; its profile induces quite some "singing".

For "real" offroad and sand riding (Tunisia, spring 2007 and 2008) I equipped the GS with Pirelli MT21 at the front and Mitas E09 at the rear. With my limited experience, I would classify the Pirelli as a good front wheel tire for desert riding; it offers quite some stability, but it also has a pronounced tendency to "climb" out of sand tracks if your speed is not high enough. The Mitas E09 "just worked"; I could not find any particularly weak point, albeit I guess that traction and direction stability in sand could be better. It lasts for more than 8 Mm. - Both tires show excellent properties on tarmac and allow cornering similar to street tires and as long as the steering head bearing is adjusted correctly the bike remains steady even at high speed. Of course they are rather noisy, due to their open profile. The tire pressure I used on tarmac was usually about 1.6...2.0 bar front, 1.8...2.3 bar rear; in the sand, I used 0.8...1.2 bar on both wheels without problems (and without tire holders). During the second Tunisia trip in spring 2008 (where we rode lots of gravel and sand roads), I used 1.1 bar everywhere, including long sections on tarmac. - The MT21 has an unusual wear pattern; it is the flank of the tire that wears out first, resulting in a somewhat "triangular" tire profile. As a result, I had to change my first MT21 after about 5500 km and the second after 6800 km, which represents the shortest lifetime I ever observed for a front tire.

Since summer 2008, I am running the Heidenau K60, initially only on the front wheel and combined with Mitas E-07, E-09 and Heidenau K60 on the rear. In spite of the open profile, the tire behaves neutral and does not exhibit any particular problems or weaknesses; I definitively consider it as a true alternative to the Mitas E-08, with much more offroad capability. As of summer 2014, I have used this tire on rough mountain trails in the Frech/Italian Alps as well as for rapid riding on tarmac, dry or wet - this is clearly a tire that fits my needs and my riding style perfectly. Lifetime seems to be varying; the first K60 on the rear wheel lasted for 8.2 Mm, the second only 5 Mm. The front tire lasts around 12.5 Mm. - In 2012, Heidenau added the K60 Scout, primarily to meet the requirements of heavy "adventure" bikes, yet both tires are still available. Lifetime seems to be a bit longer (8-10 Mm on the rear wheel).

HPN 0619

While I am active in the HPN Forum for more than 15 years, it was only during the HPN Forumstreff 2015 that I decided to order a HPN frame reinforcement.

Before this date, I was somewhat confused by the fact that most HPN bikes that I knew involved costs of at least 7 k€. I was unaware of the fact that besides these in-depth HPN Sport modifications, HPN also offers their basic frame reinforcement for a very reasonable price: as of 2017-07, the list price is less than 800 €.

I placed order in late 2015, quickly received the confirmation together with my frame number (0619) and ... waited.

In summer 2017, HPN was ready to receive my frame. Within 24 hours, I completely disassembled the bike and sent the frame to Germany. In the meantime, I changed the timing chain, changed all oils, replaced the pushrod seals, powder-coated the rear subframe, centerstand and luggage carrier, washed all cables and took care of the plastic parts.

Only five weeks later, the reinforced frame was on its way back. I received it on 2017-08-03, reassembled the bike over a period of 2 weeks and on 2017-08-20, HPN 619 hit the road for the first time!

Oil Consumption and Engine Rebuild

After about 47'000 km, oil consumption was excessive: more that 1 l per 1000 km. Some friends riding with me complained that the GS started to smoke like a two-stroke engine, especially when I had used the motor brake for a while (downhill). Upon removal of the sparks I could see that the combustion chamber of the right cylinder and the shaft of the exhaust valve were wetted with oil, so there was really something wrong. I finally decided to have the cylinder heads rebuilt.

I contacted BMW in Munich before the "operation" to ask for a refund. The first reason was that I don't consider it as normal that an 800-cm3-engine has to be rebuilt after less than 100'000 km. The second reason was that I had contacted BMW before buying the bike and asked about the "expected lifetime" of the motor (at that time, there was a long-distance test in the "Tourenfahrer" magazine which clearly stated that the engine of the 100GS needed a rebuild after 40'000 km). BMW replied 1990 that a usual lifetime of more than 80'000 km could be expected before the engine would need revision.

Well, upon my request they regretted the problems with my GS and said that it was certainly not normal that the valve guides were worn out after 47000 km, but I should please get in contact with my local BMW agency.

That is what I did and the rebuild was finally done in 1993, at about 58000 km. At WüDo in Dortmund (I was living close by at that time) this cost me about 1000 DM, with two third of that for the material and the rest for the work.

The picture shows an inlet valve (left) and an outlet valve. The colours were somewhat falsified on the scanner ... but that shows nicely the "wear and tear" on the valves.

It was found that all four valves had considerable play in their guide perpendicular to the primary axis (that is, they "wiggle" if you move them laterally). In addition, the outlet valves were completely worn out. The cylinders and pistons were nice and rather clean (except for some coal deposits, origining from the oil that had been carried in through the worn-out valves and that had burned). During the next years and up to about 120 Mm, the motor was always fine and never showed an oil consumption exceeding 0.5 l/1000 km.

With all these data, I re-contacted BMW in Munich to ask for a refund. They regretted again the problems with my GS, but "please understand that a technical defect may occur even with a BMW motorcycle and that we cannot always explain this. After more than three years we cannot participate in the costs."

The second head overhaul was performed in 2007-04, at 146400 km. It is documented on a separate page. Material costs were about 300 EUR.

Changing the timing chain

Over the years, my GS started to develop a certain amount of "mechanical noise". When you are riding the same bike all the time, you don't notice these changes as they introduce themselves very smoothly. However, if someone else listens to the noise he will be probably be able to tell you that it has changed since the last time.

That was what happened at my local BMW dealer. He found my GS rather noisy and said that it would be a good idea to change the timing chain in a not-too-distant future. Indeed the bike was rattling pretty much, which was best heard in his workshop where the noise echoed off the walls. My bike had 110'500 km on the counter and still the first timing chain. There were not apparent signs of misbehaviour, but the idea of changing the timing chain sounded reasonable to me.

Well, I asked how much he would charge for this and he answered "something like 500 CHF".

Oops.

That was the moment I decided to do it myself.

I understood later on that most of this sum of money was not for the parts; they're actually pretty cheap. Even the action of changing the timing chain "as such" is actually not difficult. The challenge is to get to it, as there is an amazing amount of stuff to be removed before you can access the chain - covers, electrics, alternator, even the exhaust downpipes and crashbar bolts have to be removed. I had never dismantled the bike as far as this and it was a real good learning experience. Here we go.

This is the list of parts that are needed, with part number updated and prices given in CHF as per June 2017 (2nd timing chain replacement). Compared to 2001 (1st timing chain replacement), prices for most parts remained rather constant (the timing chain went from 30.50 CHF to 28.05 CHF, the seal -337 654 (former -255 011) from 12.20 CHF to 8.20 CHF. For other parts, prices increased significantly: the chain tensioner went from 3.30 CHF to 8.75 CHF, its spring from 0.40 CHF to 6.10 CHF (15-fold), and the slide rail tripled from 10.40 CHF to 30.25 CHF.

--------+-----------------+------------------------------------------------
   CHF      Part number     Designation (EN/DE/FR)
--------+-----------------+------------------------------------------------
  28.05   11 31 1 335 580   Timing Chain/Steuerkette/Chaîne de distribution
   8.75   11 31 1 338 185   Chain Tensioner/Kettenspanner/Patin
   6.10   11 31 1 335 584   Spring/Feder/Ressort
  30.25   11 31 1 335 576   Slide Rail/Gleitschiene/Patin
   4.88   11 14 1 338 428   Gasket/Dichtung/Joint
   8.20   11 14 1 337 654   Seal/Simmerring/Simmerring
--------+-----------------+-------------------------------------------------

In addition, get some bright paint (correction fluid like "Tipp-Ex" is just fine), a few Nylon cable binders and high-temperature anti-seize for the exhaust nuts, e.g. copper paste, ceramic paste, or "Optimol TA". (Some people advise against the use of copper paste in connection with aluminium parts.)

Among the "unusual" tools, there is the wrench for the exhaust nuts. Hammer with plastic head. Some tool to remove the alternator (see below). Small pair of pliers. Hair dryer, or hot air gun. Strobe lamp to adjust ignition timing after reassembly.

I assume that you are in good mood, self-confident and that you have some practical experience in mechanics on this bike. If you do this for the first time, plan at least six hours - now that I have figured out a few tricks, I might be able to do it in about half of that time.

The engine must be cold and clean. This time you are really allowed to use a high-pressure cleaner, but only for the engine block.

Before starting anything else, make sure you are able to remove the exhaust downpipes (german: "Auspuffkrümmer"). You have to take them off, as the interference tube will interfere (!) with the lower part of the timing chain cover. If your downpipes haven't been removed for a while, put some thin oil ("Kriechöl") on the threads and wait a few hours, then set on the tool and rotate the nuts with a hammer. If you screw up the exhaust threads on the engine, you're in expensive trouble, so be careful.

Now we can "really" start.

1. Loosen the exhaust clamps (under the engine) completely, then remove the exhaust downpipes. Normally you won't need to loosen the interference tube. If the downpipes don't come off easily, tap from the cylinder side (inside the "main bent") with a plastic hammer to drive them out.
2. If your bike has BMW crashbars, remove the two "inner" bolts that hold the upper part of the crashbars in place. The space is too confined here to remove the timing chain cover with these bolts in place.
3. Take off the seat and the gas tank. Disconnect battery ground, and isolate that connector at the battery.
4. Remove the front engine cover, then remove the alternator stator and rotor as described in another section of this page.
5. Unscrew the diode board and take it off. On the back of the diode plate, there is a black cable coming from a "cable tree" and running through a hole in the upper portion of the timing cover. This connects to the starter solenoid ... so take off the air filter, loosen the two bolts that hold the starter cover, then slide it back and take it out to the left side. Did I tell you that we're going to disassemble a lot?
6. Remove the remaining cables around diode plate and alternator. Draw sketches or take photos of all connections if you are not sure where they go, how they are connected, or whatever. You have been warned.
7. Separate the plug for the ignition unit: slide a small screwdriver at the sides under the metal clamp and pull the plug.
8. Now we're going to remove the ignition position sensor (the "tin can" on the bottom of the case). Mark the position of the unit with paint. You will need to readjust ignition timing anyway, but marking its position will at least allow you to pre-adjust and to start the engine easily. Then, remove the two screws and pull out the timing unit. It comes off easily.
9. Now remove the nuts and bolts that attach the timing cover. There are 9 allen head screws and 3 allen head nuts. On my GS, all bolts have the same length. There will be a few drops of oil leaking out, but not much - you do not need to drain the engine oil.
10. Breathe, then pull the timing cover straight towards the front wheel. Mine came right off, but if this is not the case you should heat the area around the crank bearing (that's where the "cone" for the rotor comes out) with a hair dryer or hot air gun. There is a bearing which fits snugly into the timing chain cover, which causes the part to "shrink-fit".
11. Recover the washers for the 12 fasteners that might still reside in the timing chain cover. Clean the timing chain cover.
12. Take a moment to admire the mechanics inside, then take the paint and mark the positions of the gears (so that you can align them again later on). Correction fluid ("Tipp-Ex") worked nicely for me. Just make sure to mark not only "inside" the gears but also on their flat side - movement of the chain will remove the paint between the cogs instantly.
13. Remove the old seal. On my bike, the lower part was easy to remove, but the upper half was "baked" to the engine, so this took some time. Be extra careful not to get any debris into your engine.
14. Now back to the mechanics. There are two chain tensioners. The one to the left (ehm, yes ... "left" while you're facing the engine) is a slide rail and comes off after removal of one screw and one nut. Be sure to get the washers and the spacers that come along!
15. To remove the second tensioner (on the right), remove the circlip with a pair of pliers, then simply pull out the tensioner. The spring-loaded bolt will "shoot" forward, but don't worry about that.
16. Now, open the chain link (it should be a chain with a link, although the BMW manual says there might be an endless chain installed - you will need a bolt cutter if this is the case). Pop the clip off with a pair of pliers, then slide out the link and the securing plate. Did I mention the risk of getting "foreign bodies" into your engine? Remove the master link and the chain will open.

Time to breathe. You're exactly halfway through it. Have a break. Wash your fingers. Go check your e-mail. Relax.

Note: the old photos from the 2001 timing chain maintenance have been replaced with better pictures from the 2017 maintenance.

I took this time to examine the old versus the new parts. On my GS, I found that there was no "really considerable" wear on most parts. I could have reused the slide rail immediately and even the chain tensioner was in a pretty good shape. Its spring, however, had lost some 10 percent in length. When I suspended the old and the new timing chain next to each other, I found the old one not to be elongated. However, it was possible to lift the old chain a bit off the cogwheels and this was not the case with the new one. So there was a good reason to replace it.

By the way, if this is the third or fourth chain, you may need to replace the cogwheels on the crankshaft and on the camshaft. I've never done this, so I'll omit it here.

Time to install the new chain.

1. First of all, install the new chain tensioner (spring and piston). They cannot be inserted after mounting the chain (now, guess what I did?), so put them in first. The piston should be held in its retracted position while you install the chain (tie-down strap or zip-tie).
2. Make sure that the sprockets are still lined up correctly. I found that it is almost impossible to move the individual gears by hand, but the paint reassured me ... "just to be sure".
3. The master link must be pushed from the back of the chain and this is where it gets weird as the best position to do this is close to the crankshaft gear, where the housing is slightly retracted. After a few trials I figured out how to do it most easily:
4. Remove the spark plugs and the sparks. Put gearbox into 5th gear.
5. Put the new chain over the cogwheels so that the link will end up somewhere on the lower gear. In that position, push the old master link halfway through the chain to close it provisionary.
6. Now rotate the rear wheel until the link ends up in the "11 o'clock" position on the upper gear. The trick is now to rotate the wheel backwards until the chain link is at "10 o'clock"; if you touch the chain now at this point, it should not be under strain (otherwise repeat the forward-backward movement).
7. Now, push the new link from the back through the chain, popping out the old link (did I mention parts that could fall into the engine ?). Put on the securing plate and the clip. Note that the clip on the master link should be installed so that the closed end goes forward as the engine rotates - in the position that you have right now, the little fish should swim upstream.
8. Slip the new chain tensioner (the one for the spring-loaded piston) on its axis on the right side and put the securing clip back on. Remove the tie-down strap and make sure the mechanism is moving freely.
9. Install the slide rail on the left side. Don't forget the washers and the two spacers. This part allows to pre-tension the chain, but do not use more than 0.5 mm!
10. Turn the rear wheel a few times and verify your timing marks. Carefuly verify that you can do a whole engine rev without hitting your valves.
11. Now change the crankshaft seal that goes around the "cone" through the cover. Note its position in the timing chain cover, then take a big socket (from a 32 mm ratchet or so) and drive out the old seal from the back. Turn around the timing chain cover and put a new seal in from the front side, with the "flat" side outwards and into the same position as the old seal.
12. Put the new timing cover gasket on. There are two more gasket "shims" above the area that forms the timing chain cavity, but below the starter cover. There is nothing to seal, but tightening the upper two bolts without these shims would probably flex the cover. Simply cut two strips (best: "O-Ring" pieces) from the old gasket and fit them in here when you mount the cover.
13. Heat the timing chain cover around the crank bearing (as above, where the "cone" for the rotor comes out) with a hair dryer. No need to make it real hot, just enough so that it expands a bit (you remember the snug fit of the bearing?). Now, slip on the timing chain cover, then install the 12 fasteners. Put them on loosely first, make sure the cover is centered, then tighten them down from the inside out. Finally, give it a few taps with a plastic hammer to "relax" the crank bearing behind.

That's most of it. Now reassemble the parts that are left:

1. Install the ignition unit. Note that there is only one sense that it fits in; if required, turn its axis (on the back) 180 degrees and try again. The cable should come out in the "2 o'clock" position (I assume that you are still facing the engine).
2. Connect the ignition cable and attach it with a cable binder.
3. Connect the small black wire (coming from the engine cable "tree") to the starter solenoid. Connect the three "big" wires to U, V, W on the diode board and the blue cable to the "D+" connector on its back (you can take any of the two connectors). Install the diode plate onto the engine cover. Verify that the B+ connector is isolated from ground and that ground is really connected to engine/frame ground.
4. Re-install alternator rotor and stator and cabling. The single, 20-cm black wire connects the sideways-pointing Y on the diode board with Y down on the stator. The thick, red one connects to B+. The two wires that connect to the coal brushes are brown (D+) and black (DF). Reconnect all other cables that I forgot to mention here.
5. Install sparks, starter cover and air filter.
6. Install exhaust downpipes, using high-temperature anti-seize. Tighten fully.
7. Double-check nuts, bolts, screws, cabling. Install all the rest that I might have omitted now.
8. Reconnect battery. If there are sparks, you have a cabling problem.
9. Clean up your workspace. Any parts missing/superfluous? Hope not.
10. Start the bike. Breathe. Notice the difference in noise?
11. Re-adjust ingnition timing. Notice the difference in stability?

Have fun!

If you own a different BMW, an article from Jim Buchanan and/or from Matt Parkhouse may be helpful.

Removing and installing the gearbox

At about 116000 km, I recognised a "howling" noise coming from the gearbox of my GS. I could still ride the bike without any problems, but this noise was not normal ... so I decided to have the gearbox revised.

The bad news is that overhauling the gearbox is a job that can not be done with the tools of a do-it-yourself mechanic. To open the gearbox, you need at least the flange puller(s) from BMW and a a pneumatic wrench plus a few other tools would also be helpful.

The good news is that you can save a sound amount of money by removing and re-fitting the gearbox yourself. Removal of the gearbox is actually not very difficult, but it is a very time-consuming job: My local BMW dealer assumes some 5 hours to do the job, so this easily saved me 450 CHF even if I did "only" the removal and re-installation myself.

The only special tool needed is a 27-mm tubular key (or the 27-mm nut from a ratchet set), a torque wrench with hex inserts (to adjust the rear swingarm bearings) and a 15-mm wrench for the paralever rod. All the rest can be done with the stock toolset, although e.g. a ratchet set will speed up work considerably. - In addition, get some anti-seize (e.g. copper paste or MoS2 grease) and BMWs driveshaft grease (Staburags or MP3). - There are lots of parts to remove, so I was prepared to find myself with many screws, nuts and bolts. I used to re-attach all those nuts and bolts to their original place immediately and I used my digital camera to take lots of pictures.

So, here we go ...:

Gearbox removal

1. Drain gear oil.
2. Remove the seat, gas tank and battery.
3. Remove the air filter and the filter housing. Two Allen-head screws fix the air filter housing to the gearbox (and to the engine block); these are pretty difficult to access. A ratchet set may come handy here.
4. To remove the battery holder, remove four screws (two on each side, two at the front). Another fixation is under the battery box; this is a plastic "plug" which is inserted through the rear fender. The part can be pryed out with a flat screwdriver. Remove the fuse holder by twisting it carefully, then lift the battery box off. - You may also try to leave the battery holder in place, but I like to have as much space as possible available.
5. You do not need to remove the carburetors, but you may find it more convenient to do so (especially if you are going to clean them anyway). Stuff some clean tissue into the cylinders to prevent dirt, animals etc. going in there.
6. Use a large screwdriver to push the gear lever (behind the gearbox) forward, then remove the cable from the "hook" at the lever. If necessary, loosen the clutch cable at the handle completely.
7. Remove speedometer cable and battery ground cable from the gearbox.
8. Push the bike in the final position in the garage - you will remove the rear drive now, so it will be pretty hard to move the bike around later.
9. At the gearbox exit, loosen the clamp on the rubber bellow at the gearbox side. Use a 10-mm key with 12-point insert (see photo) to remove the four screws that hold the flange. The photo shows a key that I always carry in my toolset, but the 10-mm ring key from the stock toolset actually does the job.
10. At this point, the BMW manual recommends to loosen the engine and to shift it forward. I've never done this, as I feel it is easier to remove the swingarm with the complete rear drive attached. - Bernd Bauer pointed out that it should be possible to remove the gearbox without removing the rear drive at all. According to Bernd, it should be sufficient to remove the engine front and upper covers, remove the exhaust downpipes, unscrew the shaft drive, losen the engine front bolt and remove the engine rear bolt completely. The rear part of the engine can then be tilted upwards with a suitable car lift and removed. The advantage of this technique is that the engine can be re-set into the frame easily and that rear drive stays on the bike, allowing to move it around without the gearbox. The disadvantage is that you have to remove the exhaust lines.
11. Remove the rear wheel.
12. Remove the rear brake mechanism from the final drive (either unscrew and draw the cable, or remove the complete brake pedal assembly).
13. Support the final drive, e.g. with some pieces of wood, then unscrew the paralever "compensation" rod from the rear drive.
14. Unscrew the lower end of the shock. Swing the shock upwards and attach it e.g. with a strap.
15. Remove the plastic caps above the swingarm bearings. Inset a 27-mm tubular key or a nut from a ratchet set and loosen the screws that fix the bearings (these are attached with 107 Nm, so you will need "some" force).
16. Use an Allen-head key to remove the bearing head on both sides. The swingarm will "fall off" and can be removed by twisting it a bit.
17. On the back of the gearbox, remove the lever completely by removing its screw. Loosen the clamp at the rubber cap and carefully take it off. A number of parts will come along: A spring, a kind of piston with integrated plastic bearing, and a long rod. Put all parts aside.
18. On the gear switch lever, "unclip" the upper joint and pry out the ball seat with your fingers. You may also unscrew the whole assembly from the frame.
19. Remove the last two Allen screws that hold the gearbox in place. Draw the gearbox backwards, it comes loose. Turn it sideways so that you can remove the two-wire cable for the Neutral switch. Lift the gearbox off the bike.

Have a break. If your gearbox needs repair and you have to wait for it, this may be a good moment to clean the carburetors, or to inspect the starter motor (now that is perfectly well accessible). In addition, check the driveshaft rubber bellows for holes - now is the perfect moment to change them. To inspect the shaft drive, just pull it away from the rear drive. The joints should have some black grease oozing out. Grip both ends of the shaft drive firmly with both hands, twist and turn it in all directions - if you feel any play, the driveshaft needs repair.

The gearbox overhaul is described in another section on this site.

Diagnostics: We found that the howling noise was caused by a defective bearing. This was the bearing that is sitting on the clutch side of the outlet cam. This bearing is the "classical" point of failure for BMW gearboxes: It takes not only the radial forces from the other cams and the gear cogwheels, but also the thousands of little axial shocks from the shaft drive ... in other words, this bearing is supposed to absorb forces that it is not designed for. On my GS, it was still far from catastrophic failure, but the bearing had developed some 3 mm of axial play.

Reinstalling the gearbox

Before reinstalling the gearbox, make sure you can shift through all the gears and back. It seems that it is possible to assemble the gearbox "wrong", so that you can shift gears up - but then you are stuck ...

A second point to verify: At the exit flange of the gearbox, the seal (Simmerring) must be installed with the flat end outside. At the upper end of the seal, there is a small triangular cut-out in the housing, which formerly served as a vent ... this must be sealed, otherwise oil will leak from the gearbox into the rear drive. Don't ask me how I learned this ;-)

1. Grease the clutch spline with very few grease (the BMW manual recommends MoS2 grease but copper paste or Staburags will reportedly do the job). An excess will fly on the clutch plates and this is certainly not where you want lubrication.
2. Lift the gearbox into the frame and connect the cables for the "neutral" switch. If you forget this one, you are kindly requested to repeat the whole exercise later on ;-)
3. Carefully slide the gearbox forward until the spline "catches", then push it fully forward until it sits smooth on the back of the engine housing. There are some "guides" cast on the housing (a rubber hammer may come handy). Attach the gearbox with the bolts on the lower right and on the lower left side.
4. The following parts can be remounted in an almost arbitrary order, with the most difficult part being the re-insertion of the driveshaft into the swingarm. This is not "technically" difficult, but it may need a lot of patience ...
5. Re-attach the gear switch lever (apply grease).
6. Insert the clutch rod (long end forward). Add the bearing (the hole slides over the previously inserted rod; the metallic plate towards faces the rear wheel) and the spring. Slide the rubber cup over this assembly; probably you can not attach it yet.
7. Grease the clutch lever bearing, then install the lever onto the back of the gearbox. Use it to compress the spring underneath, so that you can now attach the bellow mentioned in the preceding paragraph.
8. Insert clutch cable and adjust clutch according to the manual.
9. Grease the spline of the driveshaft with some high-pressure grease (Staburags or MP3; this is a special high-pressure grease; do not try to replace it by standard grease). Then, insert driveshaft into rear swingarm. As mentioned, this may need a lot of patience and some luck ...
10. Insert swingarm into frame. Insert the bolts that hold the swingarm in place, but do not fully tighten them yet.
11. Apply grease and attach the rear shock loosely to hold the swingarm in place. At this point, BMW recommends to adjust the bearings. However, I found it easier to mount the complete rear drive first.
12. Attach the Paralever "compensation rod". This requires a 15-mm wrench, which is not in the stock toolset (grease the bolt with copper paste; 47 Nm; bolt head pointing to the outside, nut inside).
13. Tighten down the rear shock (29 Nm).
14. Install the rear wheel. I do this now since it allows to rotate the driveshaft easily in the next steps.
15. Reinstall and adjust the rear brake gear.
16. Re-attach the driveshaft to the flange on the gearbox. This is exactly inverse to the unmounting procedure (shown above) and can also be accomplished with the 10/12-mm ring key from the BMW stock toolset. The required torque setting is 40 Nm - however, it is almost impossible to use a torque wrench here. I used the key from the toolset and tightened as good as I could, but without using additional tools. Make sure the threads are dry (no oil!). Some people recommend to use Loctite here.
17. Attach the rubber bellow that covers the driveshaft/gearbox zone.
18. Adjust the rear swingarm so that it is centered in the frame (BMW allows a maximum difference of 0.5 mm between the two sides).
19. Using a torque wrench, pre-tension one of the swingarm bearing bolts with 20 Nm. Unscrew it again and re-tighten with 10 Nm. If you do not have a torque wrench with hex adapter, first attach it hand-tight, then release the bearing again and re-tighten carefully so that the bearing just starts to "carry". Now, tighten the nut that secures this bolt: Use a 27-mm tubular key (ratchet) and tighten fully (107 Nm). Make sure the center bolt did not move.
20. Repeat this procedure on the other side. Put the black caps back on (do not grease here, as there is a vent from the rear swingarm going to the caps).
21. Fill gearbox with oil.
22. Re-attach the fuse holder to the left side of the battery holder. Re-install the battery holder into frame (four screws plus the clip towards the rear fender). Don't forget the auxiliary plug.
23. Insert bottom of air filter housing (don't forget the gas tubing that connects both carburetors) and fix it with its three screws: one goes into the gearbox, two into the engine - these two are weird to reach. Note: Several people reported that it is very convenient to swap the two "front" bolts with those of the starter motor. Afterwards you can remove both the starter motor and the air filter housing much easier ;-). Reconnect oil drain line.
24. Re-install engine top cover, air filter, air filter cover.
25. Re-install carburetors (if you removed them). Do not confuse the cables for choke and gas ;-)
26. Connect the speedometer cable to the gearbox and attach it with is dedicated (hollow) screw, which also holds two battery ground connections.
27. Insert and connect the battery. Note that there are two +12 V lines and one ground cable.
28. Install gas tank.
29. We're done ... time to clean up. Look carefully for any parts, especially nuts and bolts that you may have overlooked. Carefully double-check everything, but in particular:
    • Rear wheel and mounting screws.
    • Rear brake.
    • Swingarm bolts and nuts.
    • Paralever mounts and bolts.
    • Rear shock.
    • Clutch adjustment.
    • Gearbox mounting screws.
    • Connection between driveshaft and gearbox flange.
    • Gearbox oil level (you don't want to ruin a freshly repaired gearbox by performing a "dry run", do you?)
30. Carefully test ride the bike.
31. I strongly recommend to check all of the above screws, in particular those of the shaft drive, after a few hundred km.
32. Have fun!

Changing the Neutral switch

At about 143000 km, I noticed oil dripping from the gearbox. Not a real "issue", but since I do not like oil stains on the garage floor it was time to change the switch.

Changing the neutral switch as such is not difficult ... the problem is getting to it, since it is located under the gearbox, right above a recess in the oil pan of the engine. To get there, you have basically two possibilities: either you remove the gearbox from the bike, or you remove the exhaust collector box and change the switch with the gearbox in place.

In the past I had removed the gearbox a number of times, so I decided to try the second path here. The part you need is the switch 61 31 1 243 097 plus its washer; total cost was about 48 CHF in late 2006. Special tools: A car lift, a hammer, eventually a torque wrench. If your exhaust system has not been disassembled for a while, add some thin oil ("Kriechöl"), a hot air gun, or whatever you prefer to get these bolts moving ;-)

1. Put the bike on the centerstand and secure it well.
2. Remove the rear wheel (this may not be necessary, but I found that it facilitated work a lot).
3. Remove the seat, the toolbox and the left side cover.
4. Loosen the exhaust clamps (under the engine, in front of the collector box) completely and do the same for the clamp that holds the main exhaust to the collector.
5. Remove the main exhaust from the bike. Depending on your particular bike, this may involve quite some additional wrenching ... on my GS, I had to remove the left luggage rack together with the left passenger footpeg and the exhaust, since the bolt holding this footpeg would not give in.
6. Remove the exhaust collector box ... i.e., simply pull it backwards.
7. Drain gearbox oil. Re-insert the drain plug once you're finished.
8. Support the engine under the rear part of the oil pan. I used a car lift here, positioned under the very end of the oil pan. In the next step we are going to remove the rear bolt that holds the engine in place, so please make sure the lift does not move! And do not forget to use a piece of wood here to distribute the weight.
9. Unscrew the left end of the engine support bolt, then drive it out towards the right. Should any of the spacers fall out, make a note of the precise location.
10. There is an aluminium tube that blocks access to the neutral switch. Remove it - on my bike, I had to use a hammer since the fit was very tight. Take the time to clean the space around there.
11. Disconnect the neutral switch, then unscrew it from the gearbox (19 mm wrench). Insert and re-connect (!) the new switch.
12. Put the aluminium tube (and the spacers) back into their location. Again, a hammer may be required ...
13. Lube the engine support bolt with some grease, then re-insert it from the right side. Tighten the nut fully.
14. Re-install the exhaust system (collector box first), with all the items that you unmounted above.
15. Re-install the rear wheel.
16. Re-fill gearbox with oil.
17. Re-install everything else that I may have forgotten to mention.
18. Have fun!

Replacing the rear crankshaft seal

Early in 2009 I noticed some oil drops on the garage floor under the engine. Upon closer inspection, it turned out that there was also some oil mist on the connection between the engine and the gearbox. The diagmosis was clear: the rear crankcase main seal was toast.

With more than 158 Mm on the engine, this was not too much of a surprise.

Changing the seal is not that difficult, but it is time-consuming since you need to strip the bike down to the bare engine. I spent about an afternoon for disassembly, changing the main seal and re-fitting the clutch and it was the first time that I did this job.

Tools: You will need all the tools mentioned under gearbox removal above, something to block the clutch in the engine housing (BMW tool number 11 2 800), and a tool to insert the new seal into the crankcase housing (BMW tool number 11 1 880). I could borrow both from my local BMW dealership :-) - In addition, get some degreaser.

Spare Parts: While you're at it, you may want to change not only the crankcase seal and the associated O-ring, but also the O-Ring of the oil pump and the simmerring at the entrance of the gearbox. Part numbers:

--------+-----------------+------------------------------------------------
   CHF      Part number     Designation (EN)
--------+-----------------+------------------------------------------------
  xxxxx   11 11 1 338 342   Crankcase/shaft seal ("Simmerring", 100X80X10)
  xxxxx   11 22 1 337 099   O-Ring/gasket crankcase 
  xxxxx   11 41 1 335 895   O-Ring/gasket oil pump
  xxxxx   23 12 1 338 726   Gearbox entrance seal ("Simmerring")
--------+-----------------+-------------------------------------------------

Disassembly

1. Remove the gearbox from the bike, as described above.
2. Position the engine at OT.
3. Mark the position of all clutch components, so that you can reassemble them in exactly the same position later on. I simply applied some correction fluid ("Tipp-Ex") at the outer rim of all parts.
4. Remove the 6 screws that hold the clutch assembly (these do not require much force), then take out the complete clutch assembly and set it aside.
5. Use two of these screws to attach the tool that prevents the crankshaft from rotating in the next step (if you do not have this tool at hand, some solid wire wound through the timing control hole may reportedly be used).
6. Remove the 5 bolts; this will require some force since they are tightened down with 100 Nm. Set the clutch housing (i.e. the part that carries the OT marks and the teeth for the starter motor) aside. You have now a free view to the leaking main seal.
7. Before proceeding further, it is of crucial importance to prevent the crankshaft from moving along its axis (if this happens, you're good for a complete disassembly of the engine). I have successfully used a piece of wood as shown in this picture; others have used T-shaped metal bars here.
8. The part with the 5 holes that is sitting on the rear end of the crankshaft needs to be removed. BMW workshops have a special puller for this, but I could remove it by simply wrapping some stiff wire around the "collar" and slightly pulling towards the back: The part came right off.
9. Removing the rear main seal is somewhat ... difficult. Plan sufficient time and patience here. Again, BMW workshops have a special tool here, but an improvised technique involving a few wood screws, prybars and not-to-be-printed vocabulary did the job ;-)

That's it - you're exactly halfway through it. Clean all surfaces thorougly. Have a break.

Replacing the seal(s)

1. Before using the new seal, it needs to be "pre-shaped". I used BMW tool 11 1 880, which is essentially a plastic cylinder with a handle. The factory workshop manual states that the new, oiled (!) seal should be left on this tool for about 2 h before use (in the german version, this information is found on two different pages: 11.32 and 11.44).
2. Use the same tool and a plastic mallet to drive the rear seal in place. Make sure it sits perfectly flat.
3. Replace the O-Ring that is located inside the part with the 5 holes that is sitting on the rear end of the crankshaft. Oil the surfaces slightly, then set in onto the end of the crankshaft.
4. While you're at it, you may also want to change the O-ring gasket of the oil pump cover, even if it is not leaking yet. Clean the parts thoroughly, then tighten down so that the oil pump cover sits flat on the engine housing.
5. In my case not only the crankcase seal was leaking, but also the seal at the entrance of the gearbox. Some oil residues together with fine sand from our two trips into the Tunisian desert (2007 and 2008) had formed an abrasive paste and contributed to the wear of the seal. Of course the seal was changed, too.

Assembly

Assembly is performed almost exactly in the reverse order of disassembly:

1. Make sure the engine is still at OT.
2. Insert the clutch housing, with the OT mark matching the timing control hole at the engine housing.
3. Attach the tool that prevents the crankshaft from rotating, then attach the small steel plate in the center with the 5 bolts (no oil - all parts must be dry). Tighten down with 100 Nm.
4. Remove the metal bar, then install the clutch components. Make sure the paint marks that you applied above are facing in the right direction.
5. Make sure the clutch disk is centered (there is no need to use the BMW tool 21 2 660, but it should be roughly centered anyway), then tighten down the 6 bolts on the rim of the clutch assembly with 20 Nm. The whole assembly now looks somewhat like shown in this picture.
6. Add a small amount of Molykote "U" to the spline.
7. Insert gearbox and finalize assembly as described above.

Changing the
front fork seal

The BMW R80GS has a 40 mm Marzocchi fork. At 110000 km, mine had an oil leak on the right fork. From the first appearance of oil mist to a leaking seal (with oil dripping out) it took less than 200 km! However, with sufficient care we could still go for 400 km with full load across four passes in the Alps. If this happens to you, make sure that you prevent the fork oil from dripping into the brake system or onto the tire! A pretty well-working solution is to take a piece of tissue (old towel or so) of about 30 x 30 cm and to wrap that around the fork, under the dust "bellows". It will absorb oil during the ride, but afterwards please park the bike somewhere where you can collect the oil that will "bleed" from this tissue.

I decided to change the seal on my own. Here's how. - Plan enough time; you may be able to do this in two hours, but you may easily need more!

1. First and most important, get the new seal (40 mm) and the right amount of the right fork oil. One seal costs about 14 CHF, so you may want to get two, "just in case".
2. Put the bike on the centerstand. Make sure that there is enough clearance below the front fork to withdraw the lower tube, so you may want to put the centerstand onto something like a big, solid plywood plate of 2...3 cm thickness (1").
3. Unmount the seat and the gas tank. You want to avoid that the bike tips over to the front, so put lots of weight on the rear part of the bike (a sandbag may be appropriate).
4. Remove the front wheel (I assume you know how to do that).
5. Remove the lower fitting of the dust bellows. Clean their inner side.
6. Remove the fender (if it's the low version).
7. Unscrew the brake saddle and fix it somehow to the upper parts of the bike. Don't let it hang around on the brake line. Depending on your fender, you may have to fiddle around a bit.
8. There is an allen-head screw in the lower end of the fork. Break is loose. Do not remove it yet - just make sure it moves.
9. Remove the lower fork stabiliser (the one that sits just above the wheel). Note the mounting direction.
10. Remove the plastic cap on the upper end of the fork. Remove the Allen bolt that sits underneath. Then, have an oil pan (or similar) ready and remove the "oil change" screw at the lower end of the fork (Philips screwdriver). Attention, the oil will "shoot" out here.
11. Now remove the allen screw in the lower end of the fork and carefully withdraw the complete lower end of the fork. I was worried about spring preload, but this is not the case as the spring is contained in the "upper" part of the fork.
12. Remove the "dust protection cap" on the lower fork tube. It comes off easily with a screwdriver. Clean it.
13. Inspect the lower fork tube. You will see a metallic ring that holds the fork seal in place. BMW says to remove it with a small screwdriver, but it is much easier said than done - this was the really time-consuming part of the work! Looking back at it, I think it might be best to try with a small pair of pliers ... and even better to replace that ring by a 41- or 42-mm Seeger ring afterwards (anybody done that? I changed my seals on a Sunday afternoon, not having access to any shop)
14. Removal of the old seal is a bit tricky. If you don't have the recommended tool, you may try to abuse the 1.5 mm Allen key from the toolbox: Hook its short end as far as possible under the old seal, then pull it upwards with a pair of pliers. In my case, the seal popped out almost instantly.
15. Clean the tube. Take care to remove any metal pieces, dust etc. that fell into the tube.
16. Grease the new seal everywhere. Put it flat onto the fork tube (closed end up) and press first with your fingers, then with a soft tool until it is in its place. You may probably use a big wrench socket.
17. Re-insert that metallic ring. Use pliers and be extra careful not to damage the new seal ... as I said, you may want to have a spare seal handy ;-).
18. Grease the seal again. Grease the "dust caps" and put them back onto the tube.

Have a break. Most of the work is done!

1. Time to reassemble! Carefully slide (push and turn) the lower tube onto the fork. Secure it with the lower Allen-head bolt.
2. Re-insert the "oil change screw".
3. Fill in the appropriate amount of the appropriate oil, then close the fork with the upper Allen-head bolt and put the plastic cap back on. I always change the damper oil in the two parts of the fork at the same time.
4. Install the lower fork stabilizer ("steep" end facing forward), but do not fully tighten the screws yet.
5. Install the brake saddle. Tighten that one firmly.
6. Install the front wheel, but do not fully tighten the screws yet.
7. "Pump" the front brake until it works again.
8. At that point, you should be able to put the bike back onto its wheels. Remove the weight from the back and get the bike off its centerstand. Push the bike a few meters and activate the fork, brake a few times - the aim of this "exercise" is to move all of the fork parts, stabilisers etc. in their "ideal" working position (by the way, I do this every time I remove the front wheel).
9. Now, finally tighten front wheel axis, axis holder, lower fork stabiliser.
10. Put back the dust bellows, re-install the fender and put back everything else that I may have forgotten to mention.
11. Clean up. Look carefully for "superfluous" parts that you may have overlooked.
12. Carefully double-check all screws that you have touched, especially on the wheel, brakes and stabilisers.
13. Carefully test ride the bike.

Have fun!

Slipping clutch

If the clutch lever starts to feels "sticky" (as if the clutch cable would break soon), you are probably encountering a problem that seems to haunt virtually all 2V GS models: The piston of the clutch mechanism ("Kupplungsdruckkolben") has swollen and is stuck in its guide of the gearbox housing. As a consequence, with a hot engine (commonly after a run on the highway) the clutch separates, but does not re-engage again ... and slips.

Luckily, the fix is rather easy: Just take off the clutch lever at the rear end of the gearbox and withdraw the rubber cap. Under this cap you will find a spring and a cylindric device that can be withdrawn with a pair of tweezers (yes, it's a bit of fiddling). This device is the infamous piston. The outer diameter of this piston must be at least 28.60 mm and at maximum 28.75 mm. You can either buy a new part (about 35 EUR), or simply have it machined down to 28.60 mm (which is what I did). Re-install everything and your clutch will be fine again.

On my GS, this happened after more than 120 Mm during a sunday afternoon ride. I don't know why this piston starts to swell after 14 years, but at least the fix was easy.

Thanks to Markus Kraus for his detailed information!

Replacing the pushrod seals

After several years, my GS showed signs of oil leakage at the pushrod base seals. This is probably not a "real" problem as long as there is just some slight oil mist, but it becomes annoying once the oil starts to drip out.

Repairing the leak "as such" is easy, as you just need to change the four pushrod seals. The bad news is that to change the pushrod seals, you need to take the cylinders off ... which means that you can spend a full afternoon with this work. However, the good news is that if you have already some practical experience in mechanics on this bike, and you are in good mood and self-confident, you can do it yourself.

Most of the work can be done with the stock toolset. As for the special tools, you need the wrench for the exhaust nuts, a hammer with plastic head, a pair of pliers for circlips ("Seegerring-Zange"), and a good torque wrench with hex inserts. A ratchet set can speed up work.

The list of parts that you are probably going to replace:

--------+-----------------+------------------------------------------------
 amount     Part number      Designation
--------+-----------------+------------------------------------------------
   4      11 32 1 262 995   Pushrod Seal/Gummistopfen/Bouchon de caoutchouc 
   2      11 11 1 337 567   O-Ring/Joint torique (Cylinder base)
   4      11 11 1 262 141   Gasket Ring/Dichtring/Anneau d'étanchéité 
   2      11 12 1 338 716   Cyl. head gasket/Zyl.kopfdicht./Joint de culasse
   2      11 12 1 338 426   Gasket/Deckeldichtung/Joint de couvercle
--------+-----------------+-------------------------------------------------

In addition, get some liquid sealant. I have used both Loctite 5926 and Würth "Silikon Spezial 250" with success, but Hylomar blue or similar material reportedly does the job (the important point is that it must resist hot oil up to 150°C at least and no acetic acid should be set free during curing). Also, get some high-temperature anti-seize for the exhaust nuts, e.g. copper paste, ceramic paste, or "Optimol TA" (Note: some people advise against the use of copper paste in connection with aluminium parts). Some degreaser or similar solvent.

If you do this for the first time, plan at least 1.5 h for the removal and about 2.5 h for the re-installation, plus ample time in between to clean the combustion chambers. I recommend to make lots of notes and pictures. Make sure you do not mix up parts: neither left and right, nor intake and exhaust ... better prepare at least two different, labelled (!) boxes for the parts.

The engine must be clean. You may want to use a high-pressure cleaner to remove oil residues and other crud, in particular abrasive stuff like sand, from the engine. You do not need to drain the engine oil.

Before starting anything else, make sure you are able to remove the exhaust downpipes (german: "Auspuffkrümmer"). If your downpipes haven't been removed for a while, put some thin oil ("Kriechöl") on the threads and wait a few hours, then set on the wrench and rotate the nuts with a hammer. If you screw up the exhaust threads on the engine, you're in expensive trouble, so be careful.

Removing the cylinders

1. Loosen the exhaust clamps (under the engine) completely, then remove the exhaust downpipes. Normally you won't need to loosen the interference tube. If the downpipes don't come off easily, tap from the cylinder side (inside the "main bent") with a plastic hammer to drive them out.
2. If your GS has original BMW crashbars, remove the lower left front bolt and its clamp. If this part is left in place, you will not be able to pull the left cylinder off later on.
3. Remove the gas tank and air filter. While this is not technically necessary, I find it more convenient.
4. Remove the carburetors and hang them e.g. over the battery, or in the air filter area. Remove the spark plugs, hang their cables e.g. over the frame.
5. Remove the valve cover.
6. Turn the crankshaft over until the piston (on the side where you are just working) is at OT and the valves have some play.
7. Undo - evenly and in stages - the four nuts that hold the rocker arms in place. Pull off the two rocker assemblies without disassembling them ... otherwise you may have a hard time putting the roller bearings back in ;-). I used a simple household rubber ring to keep the parts together.
8. Pull out the pushrods.
9. Remove the two remaining nuts that hold the head connected to the cylinder.
10. Separate head and cylinder (gently tap with a plastic hammer, if needed). Take the head off the mounting studs and carefully put it aside.
11. You may want to leave the piston inside the cylinder (this will avoid the hassle of fiddling the piston rings back in). Thus, gently slip the cylinder forward until the bolt of the piston becomes visible. Remove one of the two circlips ("Seegerring") and gently push the piston pin to the other side. The rod will come free. Pull off the cylinder with the piston inside, but please avoid that the rod drops against the crankcase.
12. Repeat the same procedure at the other side of the engine. Note that the clutch cable may slightly impede this movement on the right side of the engine, however, there is no need to remove it.

That's it ... take a break.

This may be a good time to test the heads for leaks: If you pour some solvent (alcohol) in the inlet or exhaust chamber, nothing should leak into the combustion chamber ... otherwise it's time to have the heads overhauled.

Remove all the old seals and clean the sealing surfaces from crud, sealer residue etc. You may want to take the time to clean combustion chambers and pistons ... I have used oven cleaner to remove most of the oil coal and various mechanical tools to remove the solid residues. Make sure not to scratch anything, as a scratch will act as a "crystallisation point" for the build-up of new deposits. Thus, the last step should be polishing and washing with clean, dust-free solvent.

Reassembly

1. Slip the new pushrod seals onto the pushrod tubes. Align the mold line so that it points straight downward.
2. Add the big O-ring and the two small O-Rings (for the two top studs) onto the base of the cylinder. Some people oil these O-rings slightly before inserting them. - Additional note: The huge O-ring at the base appeared somewhere during the 1980s. Initially it was a white 2.0-mm ring, later on it was replaced by 2.2 mm. The ones that I got in 2004 were black.
3. Apply very few (!) liquid sealant onto the sealing of the cylinder base, but make sure you stay at the outer part of it: do not apply any sealant to the O-Rings!
4. Slide the cylinder onto the four mounting studs, until the hole of the piston aligns with the bore of the rod. Check that you've got the right cylinder and the right piston: The arrow on the piston points forward! Install the piston pin and put the circlip back on.
5. Add the cylinder head gasket. Please note that there is only one direction in which this gasket is aligned correctly: the holes must perfectly match the holes for the pushrods. If you get this wrong, the pushrods may not be able to move freely.
6. Make sure that the crankshaft on the side where you are just working is in OT and that there are no foreign bodies that got inside, then attach the cylinder head loosely with its two nuts.
7. Do not forget to insert the pushrods.
8. Set the rocker assembly back into place. Ensure that the "dots" at the upper end point outwards, then use the screws to pull the whole cylinder/head assembly loosely but evenly into place. Follow a cross-walk pattern. Do not fully tighten the bolts yet!
9. Once the cylinder is seated in place, unscrew the rocker nuts a little bit, just enough to press the upper and lower rocker mount together by hand (this is to reduce axial play). Holding them firmly together, tighten the six nuts with a torque wrench, in the sequence 10 - 4 - 8 - 2 - 6 - 12 o'clock. First round with 15 Nm, then 25 Nm, then 35 Nm. And please ... do not try to do this without a torque wrench. I am always surprised about the huge difference in perception between 25 and 35 Nm!
10. Repeat this with the second cylinder.
11. Turn the engine over several times (e.g. by turning the rear wheel in 5th gear), then adjust valve clearance. I presume that I do not need to describe how to do this ;-)
12. Re-install sparks and spark plugs.
13. Re-install the exhaust system and the lower left crashbar bolt.
14. Re-install carburetors, air filter assembly and gas tank.
15. Put a flat oil pan under each head, then start the bike. After a few moments, oil should appear at all of the four rocker assemblies - this is to ensure correct lubrification. Is everything runing fine?
16. Stop the engine and re-install the valve covers.
17. Clean up your workspace. Any parts missing/superfluous? Hopefully not ...
18. Important: After a few hundred km, re-tighten the cylinder head bolts (again: use the cycle of 15 Nm, 25 Nm, 35 Nm) and re-adjust valve clearance. This control and adjustment is truly necessary as the head gasket will "seat" during the initial phase, which in turn reduces valve clearance. On my GS, I did this just 400 km after the gasket replacement ... and found significantly less than 0.1 mm of clearance on all four valves.
19. Have fun!

Final drive swap

Commonly, wear and tear of the final drive go unnoticed for a long time, as the noise builds up very gradually. I noticed this problem only when someone else spun my GS's rear wheel and commented on the rushing noise with "ah yes, this bearing is dead, too". Indeed the rear wheel started to have some axial play (funny enough, only in one position). A while later I noticed that the rear drive was getting very hot even after only 30 km of riding, so it was time to change.

Repairing the final drive requires exchange of the main bearing plus some delicate adjustments; common wisdom (and even BMW dealers) says that it may be cheaper to get a second-hand final drive. This is indeed what I did and in spring 2005 I changed the rear drive. The "old" one is now awaiting repair, but in the meantime I can ride the GS with the "new" rear drive ;-)

Swapping the final drive is technically not difficult, but it requires quite some tools and fine adjustments. This work is safety-related, so you should know what you are doing. Note especially the positions (depths, angles) of the major nuts, bolts and clamps before unmounting them.

You will need some tools that are not part of the stock toolset: A 27-mm ring key, a 15-mm wrench for the paralever rod, a 12-mm hex ("Inbus") key with a long extension, one torque wrench covering at least 40 to 105 Nm and another one for the range 5 to 10 Nm (to adjust the rear bearings).

In addition, get some anti-seize (e.g. copper paste or MoS2 grease), BMWs driveshaft grease (Staburags or MP3) and a thread sealant. For the latter, the BMW workshop manual lists Loctite 242 (medium stregth, can be removed with tools), their spare parts catalogue mentions 2701 (extra strong, cannot be removed without heat). I used Loctite 243, which seems to be an improved successor of the 242.

It will very probably be required to replace the two paralever bearings that are located on the left and right side of the rear drive. These are available as BMW part number 33 17 2 311 091 (needle bearing 10x32x17, FAG 10-6465A, apparently custom-made). Price was 28 CHF each in summer 2005; you need two. To exchange them, you will also need a small puller for bearings with ca. 20 mm ID and a hot air gun.

Removing the Final Drive

1. At least the rear of the motorcycle should be clean. Put the motorcycle on the center stand; remove the rear wheel.
2. Drain oil of the final drive.
3. Remove the brake liners (be careful about the spring load; wear protective gloves).
4. Unscrew and remove the brake lever; note the arrangement of the parts. Withdraw the brake cam from the inside.
5. Unscrew the two clamps that attach the rubber bellow and loosen the bellow on both ends. Watch if oil is flowing out - if yes, you have a leak either at the exit of the gearbox, or at the entrance of the final drive.
6. Use a 27-mm ring key to loosen the hex nut that secures the right ("outer") bearing pivot pin. This nut is attached with 105 Nm, so again you will need "some" force. Loosen the bolt a few turns, but do not remove it yet.
7. The pivot pin that holds the left ("inner") bearing of the final drive is sealed with Loctite. Heat it to at least 100 °C, then use a 12-mm hex key with a long (!) extension to break it loose. This is factory-tightened with 105 Nm, so you will need "some" force. Carefully remove this bolt.
8. Carefully remove the "outer" pivot pins. The inner races of the bearing will usually come off, too.
9. Unscrew the paralever rod from the rear drive. Support both the swingarm and the final drive, e.g. with some pieces of wood.
10. Unscrew the lower end of the shock. Swing the shock upward and attach it e.g. with a strap.
11. Pull the final drive off.
12. Clean the rear part of the swingarm, especially the threads of (and for) the bolts.

Have a break. Verify the bearings: If you turn the inner races of the bearing, the movement should be smooth. However, usually you will notice some "marks" here, indicating a worn-out bearing. Note: If these bearings are damaged (e.g. have developed a lot of play), carefully inspect the two pivot pins for increased wear, such as a slightly elliptical shape. In this case you will need to replace the pivot pins, too. (Thanks to Helmut Schaer for this hint!)

Changing the bearings is rather straightforward:

1. Use a puller to extract the old bearings.
2. Clean the area thoroughly, then heat to ca. 120 °C.
3. Insert the new bearings and quickly use e.g. an outer race of the "old" bearing to drive the new one into place. Note that these bearings have two distinct sides; the side where the outer race is largest (here, this was the side that carried the writing) is mounted towards the inside of the swingarm.

Reinstalling the final drive

1. Make sure the centerstand is secured, so that you cannot push the bike off the stand if you push hard on the rear end of the bike (e.g. strap-down tie between centerstand and crashbar).
2. Make sure the paralever rod is held away from the rear end of the swingarm, e.g. by pulling it away with a strap.
3. Clean the rear part of the swingarm, especially the threads of (and for) the bolts. Support the swingarm, e.g. with some pieces of wood.
4. Pull the rubber bellow over the final drive, but do not attach it yet.
5. Grease the final drive with a few grams of Staburags NPU 30 PTM or MP3. This is a special high-pressure grease; do not try to replace it by standard grease.
6. Insert the final drive into the swingarm. This is easier said than done; you may get it right within a few seconds, but it may also take quite a while ... I found it helpful to position the rear end of the driveshaft exactly in the center of the swingarm by adding some textile tissue under it; this can be pulled out once the final drive is in place.
7. Align the driveshaft roughly in its final position, then attach the paralever "compensation" rod completely (47 Nm, bolt pointing to the outside, nut inside).
8. Put the rear shock back into position and attach it loosely; do not fully tighten yet.
9. Align the driveshaft precisely in its final position. Wet the threads of the "inner" bolt with Loctite, then carefully screw the bolt in (wobble the rear drive if necessary, but do not use force). Use hand-tight first, then tighten down with 105 Nm.
10. Grease the "outer" bolt with some anti-seize (I used copper paste). With the driveshaft still precisely in its final position, carefully insert the bolt (wobble the rear drive if necessary, but do not use force) and screw it in, but not more than hand-tight.
11. The factory manual says to tighten this bolt with 5 Nm, then loosen it again a bit and re-tighten with 7 Nm. Warning: Do not try to "estimate" this ... use a torque key.
12. Put on the nut that secures this bolt (32-mm key) and tighten it with 105 Nm.
13. Reattach the two clamps that attach the rubber bellow.
14. Fully attach the nuts that hold the rear shock (29 Nm)
15. Reinstall the brakes: Insert the brake cam into the rear drive housing (from the inside). Add the brake liners (careful about the spring load; wear protective gloves). Note: The springs are installed "under" the brake liners, i.e. facing the outside. The rubber damper on ther lower back spring should be aligned so that its flat side faces the brake cam.
16. Attach the brake cable and brake lever.
17. Fill oil in the final drive.
18. Mount the rear wheel.
19. Adjust the rear brake.
20. Put back everything else that I may have forgotten to mention.
21. Clean up. Look carefully for "superfluous" parts that you may have overlooked.
22. Double-check all screws that you have touched, especially on the paralever, wheel and brakes, then carefully test ride the bike. Important: After a few hundred km, verify the bolts (I use paint marks) and ensure that the rear drive bearings do not show any play.
23. Have fun!

The difference between the worn-out and the "new" drive was striking: Spinning the rear wheel on the centerstand, I could hear no noise at all.

You may want to verify and readjust the play of the pivot bearings after about 1000..1500 km. Experienced riders recommend to verify the bolts regularly if you ride a lot of rough roads.

Oil leak!

At about 143000 km, after a holiday trip in Italy, I was coming back from a very short ride - something like 1 km to the washing place and back. The bike was barely on the centerstand when I noticed a trace of oil behind me. This was not just a few droplets - it was a real oil leak.

First I thought it was the gearbox neutral switch, but the smell of the oil was clearly that of motor oil. Since the engine bash plate was soaked in oil, too, I removed it from the bike, roughly wiped off the excess oil and re-started the engine. The oil pressure warning light behaved as usual, i.e. it went dark right after starting the engine. Letting it idle, I carefully observed the engine block.

Oil was bubbling out at the front of the oil filter cover - !

I switched the engine off and dropped the bike on the sidestand. I removed the oil filter cover and found all three bolts to be firmly in place and the oil filter as such was also in good shape. The most important item, the white O-Ring (aka "the $2000 O-Ring" since it is a critical part; it must seal both the oil filter tube/canister to the outer cover and the canister to the engine case), also was in the correct shape: slightly compressed. What was it then that caused this leak?

The question was answered by measuring the distance between the outer edge of the oil filter tube/canister ("Mantelrohr") and the flat surface of the engine block (see also a Diagram at the HPN website, annotations in German). In the past, I had always measured something like 3.8 mm here, which is just the perfect distance so that the white O-Ring is compressed, but no additional shim nor seal is required. Yet ... the value that I measured now was 4.2 mm. This meant that the tube had settled, the O-Ring with its 4.0 mm diameter would not seal anymore and oil - as well as oil pressure - was lost.

Technically, the issue could be solved quickly by inserting a suitable shim from an earlier oil change (yes, I keep those ;-) under the cover, just above the (fresh) O-Ring. However, what strikes me is that this movement of the oil filter tube occurred "out of the blue", after more than 140 Mm and 15 years, without any warning. Would I have been on a trip, it was highly probable that the loss of oil - and of oil pressure - would have gone unnoticed until it was too late :-(

My conclusion: Measure the distance described above every time you open the oil filter cover ... and, from time to time, keep an eye on that area to see if it is still dry.

• Robert Fleischer's Oil and Filter Change Procedures and Technical Information
• Michael Kräwinkel's short explanation (in German)

Muffler gaskets

In the 1990s, BMW assembled the GS exhaust system using graphite gaskets. These were soft, easy to install, often reusable and easy to replace.

Later, BMW decided to replace the graphite gaskets by aluminum sleeves. These parts have tight tolerances and require a very clean exhaust system: if you have tightened down the exhaust clamps, they will no longer fit.

This became a problem on my GS after the HPN conversion when the gaskets that I had in stock would no longer fit: now the exhaust had leaks at two transition points. Riding around with unnecessary noise, almost like a "modern" 4V GS with exhaust ... not what I like.

If you're like me, you do not want to buy a special tool to enlarge the exhaust pipes (just for one single use) ... instead, you can use "exhaust assembly paste" (I used the product from Presto). Essentially, you dismantle the exhaust system, clean and degrease all joints and sealant surfaces. Upon reassembly, proceed step by step and apply sufficient amounts of that paste in place of the gaskets, then wipe off excess paste. The paste dries out slowly and the heat from the exhaust gases will finally "bake" the paste into a solid, ceramic-like material.

With that, my GS finally sounds "normal" again :-)

History

I got my GS in 1990-05, brandnew.

Very early I noticed rusty parts on the exhaust lines. BMW changed these without problems, as they just introduced the stainless-steel exhaust system for the GS. Now I have the stainless steel "end pot", but the collector is still the original version. As it gets hot rather rapidly, there is no real need to change it.

40000 km, changed the two rubber hoses between carburator and cylinder. ID 41 mm, OD 52 mm, length 28 mm.

54850 km (1993-05). Changed the front brake liners. (now Lucas Girling 533, about 35 DM in 1992)

58000 km, 1993-08: Engine rebuild, see above.

61000 km (1993-10): First alternator trouble, see above.

63195 km (1994-01), changed Battery. Now a VARTA, which worked fine until spring 2004. After this time - ten years! - this battery died due to mechanical failure: one of the cells was no longer charged.

65000 km (1994-05): Sudden stop of the engine. It was different from the "must switch to reserve" behaviour - I was riding on the highway and all of a sudden the engine stopped as if someone had flipped the kill switch. First check, does the ignition work? No - no spark. Checked the fuses - OK. Removed the gas tank, and then I saw it: The isolation of two cables (one led to the ignition coil) was worn out, probably doe to vibrations. It took a length of isolating tape (always have a roll of that with you!) and the engine started immediately. I packed everything on the bike and rode on, the final 10 km until I arrived home. - Fortunately this was an unusual situation for a failure: A warm and sunny sunday afternoon, I was not in a hurry, only about 10 km from home, riding on a crowded street (german highway), the next emergency phone was less than 1 km away, and I had lots of time.

68000 km, 1994-06: The replacement alternator is defective, see above.

70100 km (1994-06), changed cables for gas throttle. Cable lengths are: left 1118 mm, right 1158 mm; diameter 1.2 mm, with fixation ("nipple") 6 mm diameter and 6 mm long. These are not identical with the cables of the R100GS (1130 + 1165 mm). (For the clutch, the cable is 1520 mm long with 2.0 mm diameter. One of the "nipples" is 7 mm diameter, the other is difficult to describe ... but it seems that the cable for the clutch is identical for almost all BMW airheads;-)

80000 km, 1995: The engine had starting problems and did not run well. After a long, long search I found that on one of the carbs the spring that holds the "starting carburetor" in its position was used up. The effect was like riding with the choke partially open on one of the carburetors, causing bad response. After changing the spring everything went OK!

86100 km, 1996-06: Changed rear shock, see above.

92100 km, 1997-04: Changed front fork springs, see above.

103900 km, 1999-09: And again, the alternator.

110000 km, 2001-05: Front fork seal (right) defective. Changing the fork seal is actually not very difficult, see above. Almost at the same time, changed the front brake liners - original BMW/Brembo, almost 70 CHF. I still have the impression these are not as effective as the Girling 533. Note: These lasted until 166950 km and had about 2.5 mm left when I changed them.

110500 km, 2001-06: Changed the timing chain.

111600 km, 2001-08: It's the turn of the ignition coil.

114000 km, 2002-05: New seat cover. It was not strictly necessary, but the old one looked shabby. The core is still in perfect shape.

116100 km, 2002-05/06: Gearbox overhaul. At the same occasion, carburetors overhauled (ultrasonic cleaning, new seals and gaskets, new diaphragms).

117900 km, 2002-08: Installed an LED voltage indicator.

119100 km, 2003-04: Verified the alternator brushes and found that they were barely used (2...3 mm missing). - Exchanged one of the H&B bags' mounting brackets (broken part).

124000 km, 2003-07: Minuscule - but annoying - oil leak at the oil pressure switch. Replaced; this requires a 24-mm tubular wrench, which is not part of the stock toolset.

126000 km, 2004-03/04: After ten years, the Varta battery died due to a defective cell. Replaced by a Banner 530.30. At about the same time, I changed the pushrod seals, cleaned the combustion chambers, installed a new shift lever and modified the crankcase venting system. And encountered the slipping clutch syndrome.

130850 km, 2005-05: Changed the final drive.

133500 km, 2005-07: changed the right throttle cable and modified the way these two cables are installed on the bike. I hope that I have finally found a way to remove the permanent strain from the right cable ...

139500 km, 2006-07: replaced the left throttle cable, the carburetor needles (p/n 13 11 1 337 692) and needle jets (p/n 13 11 1 260 971). Shortly afterwards, installed a handlebar riser and lower footpegs.

143400 km, 2006-10: Leaking oil filter cover, due to a settled oil filter tube! Corrected by inserting a metal washer until the expected tolerance was met. - Almost at the same time, the neutral switch of the gearbox started leaking. Replaced in 2007-01.

146400 km, 2007-04: Revised the heads (almost 90000 km after the first revision), due to high oil consumption at rpms above ~4000 rpm. The engine received new valves, valve guides, valve springs etc and the valve seats were re-grinded. Material costs were about 300 EUR.

147000 km, 2007-04: Broken spoke on the rear wheel. Replacement part numbers and prices: 36 31 1 452 737 spoke, 2.30 CHF; 36 31 1 452 727 nipple, 3.10 CHF; 07 11 9 904 003 screw, 0.30 CHF.

148400 km, 2007-07: Following an "unplanned get-off", the bike needed some repair. Replaced the right fork tube, fork brace, lower triple clamp and - while I was at it - steering head bearing, speedometer, control lamps, lamp housing and some worn-out rubber seals. I measured the frame with the BMW tool and found to be perfectly straight and symmetrical, i.e. it had not suffered any damage.

156700 km, 2008-09: The collector box of the exhaust system has developed a rust hole. Swapped against a second-hand replacement that I had acquired a while ago.

158150 km, 2009-04: Repainted the centerstand (got sandblasted in Tunisia 2007 and 2008 ;-) and replaced its worn-out bushings. Changed the leaking rear crankshaft seal and the equally leaking seal of the gearbox entrance. Cleaned and lubed the starter, changed alternator coal brushes.

165800 km, 2010-05: After only 6 years, the Banner battery started to fail. Replaced by a Kung Long WP18-12, a gel-type battery with 18 Ah. At the side of the battery there is now sufficient space for a small box, holding the most common spare parts.

166950 km, 2010-07: The front brake rotor (disc) was worn up. Replaced by a "new old" part (secondhand but 6.0 mm thick, i.e. as good as new) and replaced the brake liners; now using Lucas MCB 533 SV.

168600 km, 2010-10: After a 1500-km trip, the clutch cable started to fail, less than 1 km from my door - that's what I call a trusty steed ;-). This was still the first, factory-installed cable. Replacement p/n 3273 2 324 956, 46.30 CHF.

Summer 2012: Found the source for intermittent charging problems that had bothered me for a while. The insulation of the two cables that lead to the alternator brushes was worn right at the point where these cables touch the engine housing, probably due to vibrations.

180 Mm passed on 2013-08-12 during a gravel trip on the Ligurische Grenzkammstrasse (Route du Marguareis). Nothing particular to report ;-)

190 Mm passed on 2015-05-14 during a trip in eastern Switzerland. Nothing particular to report. I placed order for the HPN frame reinforcement.

194000 km, 2016-06. During a weekend trip in the Aosta Valley, the sidestand attachment of the left crashbar broke. A few km further, the starter motor failed due to dropped magnets. The crashbar was welded a few days later, the starter motor was replaced by a brandnew unit, obtained from Carsten Tiedemann.

197571 km, 2017-06-11. The bike is completely disassembled, the frame sent to HPN for reinforcement and to become HPN 0619. During that time I performed a bunch of maintenance tasks: changed timing chain, replaced alternator wiring, changed pushrod seals, changed all oils, ...

197571 km, 2017-08-20. HPN number 619 is alive :-)

199645 km, 2018-05. The Öhlins shock had developed an oil leak and needed an overhaul.

200 Mm passed on 2019-05-29 during the trip to the HPN Forumstreff 2019. The bike runs fine, nothing particular to report.

202360 km, 2022-05: after 12 years, the Kung Long WP18-12 battery is slowly dying. I replaced it by the same type.

Manual

You may be interested to know that the BMW workshop manual for the GS is available as a regular, official part from BMW. The booklet carries part number 01 50 9 799 000 (german version, printed 4.93) and covers the R80GS, R100GS and R100R.

I have been asked a few times what should be considered in particular when you buy a BMW "airhead" GS secondhand. The questions (and answers ;-) have been summarised in a separate document in Adobe pdf format (last updated 2018-07). Feel free to contribute!

Other GS riders

• The Airheads Beemer Club.
• The International BMW Riders Organisation.
• Motobins (UK) has a number of tech tips for BMW R and K series.
• Jim Buchanan's motorcycle pages.
• Powerboxer.de, many repair instructions. In German.
• Daniel Dicke's Website, in German.
• Gerd Oldekop's R80GS Basic, in German.
• Michael Rein's Site, in German.
• Rainer Restat has a page about his G/S and several technical background articles. In German.
• Wendell Duncan's Microfiche for the 1990-09 and later model year R80/100GS.
• Online BMW parts catalog at realoem.com.

Discussion

• HPN Forum, in German.
• www.2-ventiler.de, in German.
• The BMW-GS mailing list at micapeak.com.