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What's that whine?

skinny_tom (aka boney)

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skinny_tom (aka boney)

The story starts with a blast to Colorado Springs last fall. I didn't have a great deal of time in either direction, so I was putting in a 700+ mile day for one of the three I had allotted in each direction. I'll may write a report about it, but it goes like this: Ride 750 miles, ride 450 miles, ride a few miles visit Whip briefly for coffee and then 3 days in Colorado springs. Ride Pikes Peak but not Mt Evans because it's already closed, so ride 700 miles instead. Slip in and out of Torrey in less than 9 hours, find a bunch of charcoal ovens in the desert, ride out of Ely NV at zero-dark-thirty in 21 degree temps and make it back home.


The two full days I spent messing around (one there and one back) necessitated that I ride hard, and one of those ride hard days was 110 degrees where I sustained speeds in excess of 90 on the interstate and smaller highways for hours at a time. I suspect that the heat involved with that type of riding caused premature failure of the seals on the input shaft bearing of the transmission. I noticed a whine at the end of that day that was varying in pitch with the speed of the engine so long as the clutch was released. The only shaft in the transmission that spins at the same speed as the engine is the input shaft. Also, I remember when the input shaft on Richard's 1100RT went out, and it sounded like that, only not as bad.


It was totally rideable, so I waited until I had a few days window here and there to pull it apart, replace the bearing, and get it back together.



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skinny_tom (aka boney)

Using a guide put together by one of the resourceful ADVRiders I split the bike and pulled the transmission, and then using some printed pages from the BMW service guide I split the transmission case and pulled the internals. None of it is very hard, just time consuming. 


Once I had it apart, I could tell by feel, the subtle difference between the one bad bearing, the front bearing on the input shaft, and the rest of them. 




Believe it or not, these are all very common sized bearings that are available just about everywhere. However, the markings on them suggest there's something else at play, so I called the manufacturer and spoke with an engineer. She didn't have the specifications on hand but confirmed my suspicion that these have some BMW OEM specification that isn't part of the "over the counter" bearings. So I spend $50 instead of $25 on a new bearing at BMW and included new seals while I was at it. Some other parts too, but they're not critical to this job. The hardest part was finding a suitable replacement for the specified sealant used to marry the case halves. The Loc-Tite was pricey and hard to find. I found some anaerobic stuff by permabond that matched the requirements for a lot less.



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skinny_tom (aka boney)

The other issue is that BMW uses a special stand, spacers and dummy shafts to set up each shaft and determine the shim size. Again, prohibitive in cost for the home shop. Instead, I decided on a hokey 3-step process by which I could essentially ensure that I would have the same size, if not still within specs shaft when I was done. 

Before I took the offending bearing off, I built a home stand that would allow me to set up a dial indicator to "zero" the length of the shaft, at the inner race of the bearings.



Then, knowing there would be a lot of potential inaccuracies in this one, I measured the same length with calipers:



And then, once the bearing was off the shaft, I measured the inner race and compared it against the inner race of the new bearing:



The bearings had a difference in width of 0.005 mm that, after some research and consideration was an amount that I was not going to easily be able to adjust by changing the shim size on the shaft. Considering the tolerance for overall shaft length is 0.05 mm, so long as the original size of the built shaft wasn't at the long end of the tolerance range, I had very little chance of exceeding it. 


A chance I was willing to take. 

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