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Points to ponder; "First time it happened to me, I thought I had sucked a valve.", but then it went away and I thought what the fuck was that? Went home, checked valve clearances, timing and advance mechanism. Couldn't find anything, and since it was running fine and going down the road, I had no clue. When it happened again, I figured it must be fuel starvation at WOT. Adjusted the floats, everything seemed fine, but then it happened again! Drained oil from transmission and rear drive looking for chunks, and then pulled off the rear wheel and... voila. I knew they were worn, but the speed at which they let go (and then pulled fine as if nothing was wrong) threw me off.

To continue to work at all means that the teeth were worn unevenly. As it slipped a notch, or two, it caught fairly well as another set was worn down differently and it held.

It has never happened to me, so I only have the stories told to me by the riders. After the first jerk, when it slipped, it would catch and then quickly jerk again and again. Soon it wouldn't pull at all. Not one was ridden into my shop. They were all hauled in. It wasn't a large number though, maybe 4-5 or so.

This will never happen with regular maintenance, as it will be caught before it gets near a failure. We documented the % remaining on any wheel removal where we thought it was near 1/3 left. This gave the owner time to consider alternatives.

I have two airheads, one high milage (R90) and one low (R65). There is much more noticeable play in the driveline on the R90 when you let off the throttle. I have checked the things I can and it seems like the biggest source of slop is the rear wheel splines, which is why I have been watching them. I also get some noise in the R90 when rolling downhill with the motor off that noise has not changed since I got the bike, and a slight amount of rear braking makes it go away. I have no idea what it is.

I hope when my rear drive fails, it will give me a few hundred more mile of gentle riding to get me out of the desert. The shame of coming home on the back of a Honda would be bad, but putting 1,400 miles on my truck going back to salvage the bike is of questionable economics. Yesterday at the BMW dealership the twits there offered me $500 trade in value on it. I passed.

Just for the sake of forensic science, I dug out the slipping rear drive and here is what I found. At first glance I thought, "Hmm, there is still a flat on the tip of the gears...", but then I took some macro photos and got a closer look. Note the "s" curve of wear and the small ridge on the trailing edge: Here is a shot of normal wear for comparison:

Bamboo812 wrote:Just for the sake of forensic science

Mine is somewhere between your two photos. unfortunately closer to the first. I wonder if the "S" wear happened very fast near the end, which may mean I am closer than I think.

Another thought, the wheel had decent splines, but it spun a outer bearing awhile later. I wonder if this could have contributed to the odd wear and go/no go/go I experienced?

Those splines aren't worn enough to slip just yet. You have another problem.

Duane Ausherman wrote: You have another problem.

Diane wants to go pillion Brad.

ME, thanks, you gave me my first laugh of the day. You seem to be very dependable in that area.