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wethead/oilhead FD?


JamesW

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Something I've been curious about is what has BMW done to solve the final drive issues that plagued the oilheads and was, imo, caused by the single sided swing arm design? Have been following posts on the wethead forum and see virtually no threads about FD issues with these bikes. Could it be better quality control or change in supplier that has mitigated the problem or possibly a component design change?

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Egad! Another drive train issue to worry about? I'm aware of the drive spline issue but finally decided it was a bad match between 6-speed trans & clutch disk. What's this about a FD problem?

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Something I've been curious about is what has BMW done to solve the final drive issues that plagued the oilheads and was, imo, caused by the single sided swing arm design? Have been following posts on the wethead forum and see virtually no threads about FD issues with these bikes. Could it be better quality control or change in supplier that has mitigated the problem or possibly a component design change?

The FD design for the 1100 and 1150 boxers was completely changed with the release of the 1200 boxers. The hexhead FD failures had been mainly from blown shaft seals, which was contributed to the amount of oil in the sealed (for the earlier years, up to camhead) FD. BMW quickly changed the spec. for the oil volume required in the FD, and that had solved the problem. Camhead FD, and presumably all the newer models, also have venting of the FD. The main drive bearing in the earlier 1200s still fails, but on rare occasions, and I am assuming that had to do with the QC of the bearing itself. The wetheads have had virtually no issues of any types, but there are reports of catastrophic failures of drive u-joints, typically with the GS/GSA crowd, where they have higher chances of water ingress into the drive housing.

 

BTW, you do know the root-cause of the FD bearing failures for the 1100s, 1150s, and the K bikes of similar vintage, right?

 

Added Note: the 1200s do NOT have any spline issues whatsoever. That design was also changed with the 1200s. My suggestion is that you should NOT break down the FD to lube the spline. It doesn't need it, and if you don't replace the rubber boot back, and sealed properly, you might run into the u-joint issue! The spline do NOT need lubing, and it's virtually dry from the factory!

Edited by PadG
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The ring (large) bearing was also upgraded on the 1200.

BMW sent a bulletin out actually recalling the original bearing we all had in stock and superseded to an upgraded bearing that arrived several weeks later. The old was on a "stop sale"

The vendor was changed, or BMW changed the spec on the bearing to a better bearing or something.

The quantity of oil could be a "chicken or the egg" thing as tiny fly specs of black gear oil on the rim was the early tell-tale that the seal was going because the bearing was going and the fluid was black with metal.

But the end result was, with the new bearing and ok, the lower fluid level, the 1200 FD failures all but ceased after the updated bearing was installed.

 

As far as single sided swingarm, the twins have had that going back to the 80's with the Airheads and the K bikes have all been single sided,

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"BTW, you do know the root-cause of the FD bearing failures for the 1100s, 1150s, and the K bikes of similar vintage, right?"

 

If I remember correctly the 1100/1150 FD issue was mainly caused by wrong tension on the large bearing caused by improper shimming. As far as FD oil quantity the 1100/1150 FDs had vents so overfill was never an issue associated with seal failure.

 

If you have an R1100RS and wanted to perform preventive measures to avoid possible future problems what steps, if any, would you take? I am using 80w90 Motul dino lube with molybdenum in hopes of avoiding the issue but what, if any, further preventive measures should one take? I want to keep my R1100RSL for the rest of my life.

 

Single sided swing arms are not a new concept and don't necessarily cause FD failures if all else is designed and built correctly but nothing does it as well as a double sided swing arm with an axle turning on tapered roller bearings. Large ball bearings are not the idle component to use to support half the weight of the motorcycle.

 

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Something I've been curious about is what has BMW done to solve the final drive issues that plagued the oilheads and was, imo, caused by the single sided swing arm design? Have been following posts on the wethead forum and see virtually no threads about FD issues with these bikes. Could it be better quality control or change in supplier that has mitigated the problem or possibly a component design change?

 

Afternoon James

 

Well!-- there have been a number of final drive changes since the 1100 final drives.

 

The 1100/1150 bikes had a number of failures, mainly due to crown bearing disintegration, it was originally blamed on bearing shimming, then blamed on the number of balls in the crown bearing, then blamed on the ball separator in the deep groove bearing, then just blamed on BMW.

 

It sure could be a bad initial shimming but that doesn't explain the number of bearing reoccurring failures after proper bearing shimming, it could be due to the bearing ball count but that doesn't explain the number of failures after the bearing was changed to 17 ball from the 19 ball then back to the 19 ball again.

 

It sure could be due to inferior ball separators but that would have to be across all the bearings over the years (doubtful).

 

It could have been from a stack-up of the above in the bad final drives.

 

I have installed number of final drive bearings over the years & on most I could see a dirt/impurity path on the ledge just under the vent. I can't say for sure if this IS/WAS the cause but having dirt, sand, road grime enter though the vent sure didn't help. (BMW must have caught on to this venting allowing dirt in as one of the upgrades on the 1200 final drives was to eliminate the vent)-- It did help the 1200 dirt ingestion but brought on other issues like seal leaks & grimy road water/junk drawn into the sealed bearing housing.

 

On my last few BMW 1100's & 1150's I actually ran a remote vent hose from the final drive vent into the air cleaner box, or up under the seat --I can't say for sure that was the answer but I never had another bearing failure on a remote vented 1100 or 1150 final drive. (could be dumb luck or it could have stopped the bearing issues, no way to know for sure). I sure wouldn't take an 1100 GS or 1150 GS across river crossings or way back into mud or axle deep sand without remote venting the final drive though.

 

Now on the first BMW 1200 (hexhead) BMW tried to address the shortcomings of the 1100/1150 final drives but some of the FIXES brought on new & improved problems.

 

As mentioned above they eliminated the final drive vent, that kept all the venting induced crud out but allowed the cooling (contracting) final drive air chamber to go to negative pressure & suck in water into places that shouldn't have dirty water. BMW also sold those early 1200 bikes as life-time final drive gear oil bikes (no changes needed)--Obviously that didn't work.

 

On the later 1200 hexhead bike BMW added a bottom drain plug & even a fill plug then went back to recommended gear oil changes (this helped).

 

They also moved the crown bearing to it's own sealed chamber & lubed it with it's own sealed grease ( didn't run in the gear oil any longer).

 

At about the same time they lowered the final drive fill amount to below the seal height & that also increases inter air space volume (another positive move from BMW) .

 

The late hexhead final drives only had one REAL PROBLEM & that was the basic bearing housing design. I wish I knew what BMW was thinking but they designed the side cover, axle, & bearing to be press fit on all sides. No wiggle room on this fit AT ALL. If ALL the dimensions were machined PERFECTLY & the bearing was a reasonably close to it's C-factor rating then you ended up with a good long lasting drive. If any one of the 3 were out of spec even a little then they failed crown bearings. They didn't have a LOT of failures but on the ones that did fail they had repeated failures until BMW authorized a new replacement final drive. But even the good dives could suck water & junk into the bearing housing due to no venting.

 

The hexhead final drive did have an alloy wheel flange that was prone to failure but BMW addressed that with a massive recall & steel flange install. But this again brought on some additional final drive failures due to the tec doing the work overheating the flange to install it, of getting it part way on then having it not move so they either re-heated it way too hot while still on the axle, or beating it the rest of the way on with a large hammer.

 

About the camhead release time BMW went back to adding a vent to the final drive BUT this vent was different as it used new porous membrane to keep dirt & water out (THIS seems to work). I think they also addressed the bearing press fit (or employed a better inspection process) as very few crown bearing failures in the camhead bikes. The vented final drive is now (I think anyhow) the official replacement for the old non-vented hexhead drive.

 

The 1200 water head bike final drive is flipped over ( shouldn't effect anything)-- As to it's good or bad I really can't say I haven't had to go into one yet. Good thing as there are very few parts available for them.. I t-h-i-n-k BMW also went back to a gear oil lubricated crown bearing (won't know for sure until I have to tear one apart). It s-e-e-m-s that BMW now has a handle on the final drive issues (or at least until they get sloppy & lax then something in the build process could bite them.

 

 

 

 

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Thanks very much for that D.R. you have explained much. I had heard about remote venting the final drive and I will do this now for sure.

 

You know I had an '86 K75C with a single sided swing arm and don't recall ever hearing or reading about FD issues. Of course this was before the internet and information wasn't as plentiful or as easy to obtain. The later airheads also were single sided as well and again apparently had no issues.

 

The only thing I can see that is is an advantage to single sided swing arms is easy fast rear wheel removal. I guess esthetically the single sided swing arm is more attractive than double sided but that would be a matter of opinion.

 

Anyway, I'm going to run that remote vent line asap.

 

Thanks again for your input D,R.

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DR - For the old style FD, it was proven quite conclusively that shimming was the root cause of the failure. That was done in the other forum, BMWLT, quite a few years back. I had participated in the discussions. The reason that people had been getting repeated failures, after getting their dealer to "repair" the failed FD is because they simply don't know what they were doing! The dealer will, typically, take the drive apart, and replace the bearing, USING THE SAME OLD SHIMS! What they were supposed to do was to take some measurements (there is a procedure for that) to recalculate the proper shim thickness to use for a given bearing. Bearings have a relatively loose width tolerance, and the differences from one bearing to another is more than enough for the necessity of recalculating the needed shim thickness. Back then, there were two members of that other forum who had been rebuilding the FD for those who wants the work done properly, and none of those rebuilt had ever failed. One guy, of the two, is still providing that service.

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DR - For the old style FD, it was proven quite conclusively that shimming was the root cause of the failure. That was done in the other forum, BMWLT, quite a few years back. I had participated in the discussions. The reason that people had been getting repeated failures, after getting their dealer to "repair" the failed FD is because they simply don't know what they were doing! The dealer will, typically, take the drive apart, and replace the bearing, USING THE SAME OLD SHIMS! What they were supposed to do was to take some measurements (there is a procedure for that) to recalculate the proper shim thickness to use for a given bearing. Bearings have a relatively loose width tolerance, and the differences from one bearing to another is more than enough for the necessity of recalculating the needed shim thickness. Back then, there were two members of that other forum who had been rebuilding the FD for those who wants the work done properly, and none of those rebuilt had ever failed. One guy, of the two, is still providing that service.

 

Remote vented my FD to the air cleaner yesterday for a total cost of about $3 and about 2 hours. A small price to pay to eliminate a possible problem area. I have thought about having my final drive shimming checked by someone familiar with the procedure but that someone is hard to find and would require some down time so definitely a winter project. Further investigation looks like I could do the check myself so I might just do it this winter.

 

I think D.R. pretty much covered all possible causes for the FD failures and he didn't say that FD bearing shimming wasn't a cause.

 

I can definitely say that my final drive did suck in a quantity of water once when I washed the motorcycle after a ride and the FD was hot when I began washing. As luck would have it I changed the FD oil within just a couple days after the washing. I actually flushed the drive with kerosene then filled with dino 80w90 and drained then filled again. I now use only Motul 80w90 with moly in the FD and transmission. The Motul certainly quieted the noisy M93 transmission, big difference.

 

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DR - For the old style FD, it was proven quite conclusively that shimming was the root cause of the failure. That was done in the other forum, BMWLT, quite a few years back. I had participated in the discussions. The reason that people had been getting repeated failures, after getting their dealer to "repair" the failed FD is because they simply don't know what they were doing! The dealer will, typically, take the drive apart, and replace the bearing, USING THE SAME OLD SHIMS! What they were supposed to do was to take some measurements (there is a procedure for that) to recalculate the proper shim thickness to use for a given bearing. Bearings have a relatively loose width tolerance, and the differences from one bearing to another is more than enough for the necessity of recalculating the needed shim thickness. Back then, there were two members of that other forum who had been rebuilding the FD for those who wants the work done properly, and none of those rebuilt had ever failed. One guy, of the two, is still providing that service.

 

Remote vented my FD to the air cleaner yesterday for a total cost of about $3 and about 2 hours. A small price to pay to eliminate a possible problem area. I have thought about having my final drive shimming checked by someone familiar with the procedure but that someone is hard to find and would require some down time so definitely a winter project. Further investigation looks like I could do the check myself so I might just do it this winter.

 

I think D.R. pretty much covered all possible causes for the FD failures and he didn't say that FD bearing shimming wasn't a cause.

 

I can definitely say that my final drive did suck in a quantity of water once when I washed the motorcycle after a ride and the FD was hot when I began washing. As luck would have it I changed the FD oil within just a couple days after the washing. I actually flushed the drive with kerosene then filled with dino 80w90 and drained then filled again. I now use only Motul 80w90 with moly in the FD and transmission. The Motul certainly quieted the noisy M93 transmission, big difference.

 

 

Afternoon James

 

Careful to not use too much moly in your final drive. Years ago the MoCo that I work for had a number of rear axle carrier bearing failures due to a last minute change to a high moly gear oil.

 

That moly is just great for high loading gear tooth contact wear but turns out not so good for bearing life as the moly would coat the bearing rollers then build up on the rollers & tighten up the bearing clearance.

 

The BMW final drive has little to no gear wear issues but lots of bearing issues so high molybdenum concentration really isn't needed.

 

If it wasn't for that darn hypoid gear set in the final drive then the final drive spool bearings would probably do best in plain old 30 weight motor oil.

 

 

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DR - For the old style FD, it was proven quite conclusively that shimming was the root cause of the failure. That was done in the other forum, BMWLT, quite a few years back. I had participated in the discussions. The reason that people had been getting repeated failures, after getting their dealer to "repair" the failed FD is because they simply don't know what they were doing! The dealer will, typically, take the drive apart, and replace the bearing, USING THE SAME OLD SHIMS! What they were supposed to do was to take some measurements (there is a procedure for that) to recalculate the proper shim thickness to use for a given bearing. Bearings have a relatively loose width tolerance, and the differences from one bearing to another is more than enough for the necessity of recalculating the needed shim thickness. Back then, there were two members of that other forum who had been rebuilding the FD for those who wants the work done properly, and none of those rebuilt had ever failed. One guy, of the two, is still providing that service.

 

Remote vented my FD to the air cleaner yesterday for a total cost of about $3 and about 2 hours. A small price to pay to eliminate a possible problem area. I have thought about having my final drive shimming checked by someone familiar with the procedure but that someone is hard to find and would require some down time so definitely a winter project. Further investigation looks like I could do the check myself so I might just do it this winter.

 

I think D.R. pretty much covered all possible causes for the FD failures and he didn't say that FD bearing shimming wasn't a cause.

 

I can definitely say that my final drive did suck in a quantity of water once when I washed the motorcycle after a ride and the FD was hot when I began washing. As luck would have it I changed the FD oil within just a couple days after the washing. I actually flushed the drive with kerosene then filled with dino 80w90 and drained then filled again. I now use only Motul 80w90 with moly in the FD and transmission. The Motul certainly quieted the noisy M93 transmission, big difference.

 

 

Afternoon James

 

Careful to not use too much moly in your final drive. Years ago the MoCo that I work for had a number of rear axle carrier bearing failures due to a last minute change to a high moly gear oil.

 

That moly is just great for high loading gear tooth contact wear but turns out not so good for bearing life as the moly would coat the bearing rollers then build up on the rollers & tighten up the bearing clearance.

 

The BMW final drive has little to no gear wear issues but lots of bearing issues so high molybdenum concentration really isn't needed.

 

If it wasn't for that darn hypoid gear set in the final drive then the final drive spool bearings would probably do best in plain old 30 weight motor oil.

 

Good afternoon DR - are you sure that the reason you stated is correct? I submit that the reason why moly makes any rolling type bearing fail is simply because those bearings, whether it's roller or ball, depends on friction to work! That's why they are always installed with a given amount of preload on the balls/rollers and the races. Without friction, they will not roll, but slide, and you know that sliding is bad, because that's when things starts to wear!!

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DR - For the old style FD, it was proven quite conclusively that shimming was the root cause of the failure. That was done in the other forum, BMWLT, quite a few years back. I had participated in the discussions. The reason that people had been getting repeated failures, after getting their dealer to "repair" the failed FD is because they simply don't know what they were doing! The dealer will, typically, take the drive apart, and replace the bearing, USING THE SAME OLD SHIMS! What they were supposed to do was to take some measurements (there is a procedure for that) to recalculate the proper shim thickness to use for a given bearing. Bearings have a relatively loose width tolerance, and the differences from one bearing to another is more than enough for the necessity of recalculating the needed shim thickness. Back then, there were two members of that other forum who had been rebuilding the FD for those who wants the work done properly, and none of those rebuilt had ever failed. One guy, of the two, is still providing that service.

 

Remote vented my FD to the air cleaner yesterday for a total cost of about $3 and about 2 hours. A small price to pay to eliminate a possible problem area. I have thought about having my final drive shimming checked by someone familiar with the procedure but that someone is hard to find and would require some down time so definitely a winter project. Further investigation looks like I could do the check myself so I might just do it this winter.

 

I think D.R. pretty much covered all possible causes for the FD failures and he didn't say that FD bearing shimming wasn't a cause.

 

I can definitely say that my final drive did suck in a quantity of water once when I washed the motorcycle after a ride and the FD was hot when I began washing. As luck would have it I changed the FD oil within just a couple days after the washing. I actually flushed the drive with kerosene then filled with dino 80w90 and drained then filled again. I now use only Motul 80w90 with moly in the FD and transmission. The Motul certainly quieted the noisy M93 transmission, big difference.

 

 

Afternoon James

 

Careful to not use too much moly in your final drive. Years ago the MoCo that I work for had a number of rear axle carrier bearing failures due to a last minute change to a high moly gear oil.

 

That moly is just great for high loading gear tooth contact wear but turns out not so good for bearing life as the moly would coat the bearing rollers then build up on the rollers & tighten up the bearing clearance.

 

The BMW final drive has little to no gear wear issues but lots of bearing issues so high molybdenum concentration really isn't needed.

 

If it wasn't for that darn hypoid gear set in the final drive then the final drive spool bearings would probably do best in plain old 30 weight motor oil.

 

Good afternoon DR - are you sure that the reason you stated is correct? I submit that the reason why moly makes any rolling type bearing fail is simply because those bearings, whether it's roller or ball, depends on friction to work! That's why they are always installed with a given amount of preload on the balls/rollers and the races. Without friction, they will not roll, but slide, and you know that sliding is bad, because that's when things starts to wear!!

 

Afternoon Pad G

 

I'm 100% positive. We ran test after test, long durability runs, loaded vehicle runs, chassis dyno runs & you name it we tested for it. This wasn't an easy thing to isolate let alone define once we found it. We needed to catch a bearing failure at just the right point of failure prior to it self destructing to the point of not being able to tell what happened.

 

Skidding bearing rollers or balls have been talked about for years but that just doesn't happen (at least according to our highly experienced bearing experts).

 

 

 

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Hi DR.

 

I don't want to belabored the point, since it's purely academic. I have no question that the bearing failed due to the moly, but was questioning whether it failed due to bearing skid or the moly (presumably molybdenum-disulfide) taking up clearance. The moly coating should be just molecular thickness, is what I am thinking!

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Hi DR.

 

I don't want to belabored the point, since it's purely academic. I have no question that the bearing failed due to the moly, but was questioning whether it failed due to bearing skid or the moly (presumably molybdenum-disulfide) taking up clearance. The moly coating should be just molecular thickness, is what I am thinking!

 

Afternoon PadG

 

Yes, if the gear oil moly additive was just a diluted molybdenum-disulfide in a thin carrier then, yes, it would probably only add a thin molecular thickness, but most moly gear oil additives are not like that. They are usually designed to have additional adhesion and cohesion additives so as to stick to the gear teeth under load.

 

The problem that I mentioned above with the moly build up was a multi department investigation as the original blame was thought to be a supplier-build bearing-shimming issue & for a while that even seemed logical as we recovered a number of vehicles built in that time frame then re-shimmed the carrier bearings to nominal specs, tightest spec & loosest spec then tested the nuts off of those vehicles (we didn't see any early bearing failures so the shimming MUST have been it, eh!)

 

Well the problem was still happening in the field even after a separate inspection process was implemented to assure correct bearing shimming.

 

Turns out when we re-shimmed the bearings we refilled the differential with a different gear oil (without the heavy moly additive).

 

I was only involved in the testing & set-up part as the drained gear oil, failed bearings, & in some cases complete rear axle assemblies were sent to the appropriate labs or suppliers to do the evaluations & measurements.

 

 

 

 

 

 

 

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i should mention that I didn't use a separate molybdenum additive. I used Motul SAE 80w90 mineral based gear box oil that contains or is reinforced with MoS2 which is a molybdenum derived additive. It is a high pressure lubricant. Of course I have no idea how much MoS2 is in this oil. About all i observed was a large reduction in noise coming from the M93 transmission. One 1L bottle does both transmission and gearbox.

 

Also, imo, while single sided swing arms can be as reliable as double sided units a double sided swing arm with associated load bearing axle is not as likely to experience failures as observed with the 1100/1150 BMWs. I would like to know what BMW did differently in the early "K" bikes (K100 K75) to avoid FD issues.

 

D.R., If I read your post correctly after you re-shimmed the bearings you filled the FDs with oil not containing any moly and still experienced the same failures as you did with oil containing moly?

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i should mention that I didn't use a separate molybdenum additive. I used Motul SAE 80w90 mineral based gear box oil that contains or is reinforced with MoS2 which is a molybdenum derived additive. It is a high pressure lubricant. Of course I have no idea how much MoS2 is in this oil. About all i observed was a large reduction in noise coming from the M93 transmission. One 1L bottle does both transmission and gearbox.

 

Also, imo, while single sided swing arms can be as reliable as double sided units a double sided swing arm with associated load bearing axle is not as likely to experience failures as observed with the 1100/1150 BMWs. I would like to know what BMW did differently in the early "K" bikes (K100 K75) to avoid FD issues.

 

D.R., If I read your post correctly after you re-shimmed the bearings you filled the FDs with oil not containing any moly and still experienced the same failures as you did with oil containing moly?

 

Morning James

 

No, we didn't get any failures with the non moly gear oil on properly shimmed bearings. (I probably didn't write it in a way easy to understand).

 

Don't let the moly thing bother you too much as the gear oil we had issues with had a very high moly content. My comment above was more to the point of don't go real heavy on the moly content (like don't add additional moly additive to a moly containing gear oil)

 

Moly is great for good tooth wear prevention so if you have gear wear issues then use moly, if no gear wear issue then moly is not needed.

 

Best prevention on the old 1100/1150 bikes is to simply change the gear oil often in the final drive (like at engine oil change, or rear tire change) as it doesn't hold much oil. Then simply strain the removed gear oil through a coffee filter, or paper towel (easier said than done though).

 

Then take the strainer media with anything in it out into the sun & look for spaklies. Also run any hard particles found in the strainer media or found in bottom of drain pan between your finger & thumb. If you feel anything sharp feeling that is usually a sign of future bearing issues (nice soft gray or black sludge is normal & isn't an issue).

 

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Good morning DR - interesting data! Thanks. The moly have been around a very long time, as additive, and I had even used the stuff in my Triumph back in the '60s.

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Morning D.R.,

OK, thanks for the clarification. I might use just straight mineral gear lube in the FD and just Motul in the transmission. Think as a winter project I'll check the carrier bearing clearance just to make myself feel better.

 

I think BMW should copy the Yamaha (FJR) drive train. Really is not a good idea to ask a carrier ball bearing to support half the weight of the motorcycle. And then we have the driveshaft design with two U-joints.....just nothing like German engineering, NOT!

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Changed out the FD oil from Motul with MoS2 to good old Valvoline 80w90 mineral oil. Going to continue to use the Motul with MoS2 additive in transmission. Just better to be safe than maybe sorry.

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