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Clutch input splines mostly stripped


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Today I nipped down to Steve's house to finish off digging onto Steve's Broken Bike - it has been a while but between my schedule and winter weather (Steve has no garage to work in), this has been the first opportunity since October to look at it.


Well we got the bike stripped and the gearbox off - after a few minor problems including having to drill the head off of the screw on the clamp holding the rear brake lines to the gearbox.




What we found was pretty much what we had feared, but not quite. The splines in the centre of the clutch plate were toast - completely stripped:




The gearbox input splines however were only partially worn - damaged but not stripped:




The clutch pressure plate and driven plate are pitted and so the whole clutch will be swapped out but as yet we do not know if we can live with those damaged splines on the gearbox. I am going to talk to Steve Scriminger, a well respected UK gearbox rebuilder, to ask his opinion but I would also welcome input from this forum (especially if your name is Anton.....)





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Afternoon Andy


Those input shaft splines are worn enough to take a new clutch disk out in a short time. How long I can’t say but no way would I put one back together with a worn input shaft like that.


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Good Afternoon (well Good evening, it is 10:40pm here),


that is pretty much what I thought, but I was hoping to hear otherwise as I know Steve will need to save up for a while before he can afford to get the gearbox rebuilt.



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Wow! How did they get like that???? Did you buy the bike from someone else who really beat the crap out of it? Sorry to see what you have lying in front of you, I wouldn't be too thrilled either.

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Ugh....that brings back some bad (and expensive) memories.


You couldn't pay me enough to put that back together and ride it with the splines in that kind of condition. I went through this same type of thing a few years ago when I was supporting my wife through nursing school and my bike was my main source of transportation. My clutch started slipping and when I went to replace it, I found that the splines were about to strip. I came down to two options


1. Find a replacement transmission

2. Rebuild the transmission


After opening my transmission up, I found that the guts were in surprisingly good shape considering it had 100k miles on it at the time. I decided to rebuild it with a new input shaft, and everything has been good for another 30k miles so far.


Here is a link to my adventure LINK


Good luck, and feel free to fire away with any questions.

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Hi there, I´ll go with a new shaft. If have too choose would only change the friction plate (the rest of the clutch assembly is almost the cost of the input shaft). Usually you can live with an old spring plate and pited pressure/coverplate, witout even notice, but not with those splines.

Best regards


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You should replace the input shaft and some mechanics ( Anton L. ) also recommend changing everything from the engine crank shaft to the transmission. ( flywheel/clutch housing, all pressure plates, clutch plate, etc. ) on the assumption there probably is a runout misalignment rather than an axial misalignment which lead to the spline failure. I'm not sure there is data to support this recommendation, but Anton certainly knows what he's talking about. When mine failed at 43,000 miles, I just replaced the input shaft and main input shaft bearing, all tranny seals, and the clutch plate. I've then undertaken pulling the transmission every winter and inspecting the splines and regreasing them. I've got about 30,000 miles on the new splines and the wear is minimal, but I'm watching the splines closely because the wear probably accellerates as the wear gets worse.

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Wow! How did they get like that???? Did you buy the bike from someone else who really beat the crap out of it? Sorry to see what you have lying in front of you, I wouldn't be too thrilled either.


I am not sure if you know or not, but than can be a relatively common problem on some of these bikes. There seems to be a period when it was worse, and mis-alignment problems were common.

So no one had to 'beat the crap out of it'.....sadly, BMW did it for them.


Steve, you have my sympathy.



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Loose crankshaft main bearings could also cause premature transmission input shaft spline failure.


A lot of problems will show up if the engine rotation axis doesn't exactly match the transmission input shaft axis.

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I don't think this is caused by Main Bearings. I think there would be more serious problems.

nrp, I think your second paragraph is the point, the transmission is misaligned from the engine. The problem is, how to elliminate it. I guess a gearbox swap is the most dependable way.

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Measuring the alignment of a local spline failure (TIR between the engine crank and input bearing bore) with a kludged fixture, I found that the rear main was about .007 thou loose - and in a strange diagonal axis, which happened to correspond to the direction of the alignment error.


I am speculating that an initial alignment error caused excessive wear on both the spline and on the rear main bearing while placing a lot of radial load on the transmission input shaft bearing too.


Others have reported that the flywheel face etc are burned as the clutch disc is dragged around the flywheel face every engine revolution.

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I have a 2001 R1150RT and it has a history of destroying input shaft splines.

39K Km. BMW completely rebuilt the g/box and replaced the clutch.

38K BMW completely rebuilt the g/box and replaced the clutch.

5K BMW completely rebuilt the g/box and replaced everything from the flywheel back.


They have consistently claimed they could not find any evidence of misalignment. It is now less than 1K since the last rebuild.


The bike has always had a bad vibration over 4K revs and by 5.5K revs it was so bad it felt as though the bike was going to self distruct so I always kept it below the vibration point.


Interestingly, this time the vibration is dramatically reduced and I have reved it out to 6K and I felt reasonably comfortable at these engine speeds.


The only apparent difference with this rebuild is the replacement of the clutch carrier etc. Possibly this was the culprit all along.






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Hi George, I wonder if on the other occasions that it had been rebuilt, it had been put together without installing it with a 120 degree offset of the major clutch components. All of the white marks need to be 120' apart when re-assembling the clutch assembly (flywheel, center pressure plate and outer pressure plate), get them reasonably close. Failure to do this may/will cause vibration and you will have to pull everything apart and do it over .



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I found that to be very interesting. I would have thought you'd line them up, but I guess they are marking where they are balancing , and perhaps that is based on access.


Keep in mind my biggest wrenching activity has been removing one panel... That thread of Keith's blew my mind.

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A balance issue (i. e. the white dots) will cause vibration, but won't cause the same failure problem as a misalignment issue. The burned flywheel face suggests the clutch disc is being drug around the flywheel face every engine revolution because of radial misalignment between the engine axis and the transmission axis.


How did they check misalignment? It requires a dial indicator mounted onto the flywheel, reading the transmission input shaft bearing housing bore. Run out should be less than about .003 inches.

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