The bad news is that the splines on the shaft are pretty worn.
Has anyone on this forum tried filling the area where the splines live with gear oil as detailed at the thread below? It sounds like the gear oil works itself up the shaft and then drains back down and repeats over and over One guys is claiming one of the Bob's BMW guys did it with great success and it significantly reduced spline wear (300,000 miles rumored). https://forums.bmwmoa.org/showthread.php?58425-1985-K100-Drive-shaft-splines/page2
Pulling a quote from the other website:
Seems pretty simple and effective; essentially:
1. Drill and tap a hole to use to be able to add the gear oil.
2. Seal interface of rear drive and swing arm.
Your moto's driveshaft splines are worn but I wouldn't see them as
badly worn. With regular attention, they might run for ten or twenty thousand miles, and maybe even more than that.
You've asked if a forum member has done this modification. I'd suggest tracking down the source of the post that presented this mod and asking them how it's going. Eight years have elapsed. I'd have some questions for the poster and have some for anybody who has done this.
As far as the modification you've described goes, the lubrication recommended for these parts is a
molybdenum paste. Which gear
oil would you use. Where on the assembly is the fill hole to be tapped. How large must it be to allow visibility of the shaft's oil level? How would it be sealed? Will there be pressure created by heat? Will the front end of the driveshaft socket be sealed? If the oil is migrating away from the shaft to
drain back, what's lubricating the shaft before then? What would be the oil replacement interval? How would it be drained? What would be the inspection interval?
The molybdenum in moly paste acts as a transfer metal created by friction. It is bonds onto the metal surfaces then is burnished by contact and that's how it lubricates and inhibits corrosion or fretting of the interacting parts, and why it is used sparingly. Excess application impedes the transfer process. The protection needs periodic renewal. Metallic surface should be cleaned and dried before application so optimal bonding will occur.
The durability of these shafts in the monolever system seem unpredictable; they seem more long-lived in the paralever system according to many posts. The lifespans of driveshaft and input splines have been inconsistent as reported on this site. Chris Harris has a video explaining why transmission input splines in six-speed versions of some motos—e.g., R1150, R1200—were wearing faster than those in the five-speed models. He seemed to attribute
some of the excessive spline wear to the racking rotational/forward and backward motion of the shafts created by operating at low revs—riders jogging along in a gear that is too high and not optimal for the speed. The remedy was to shift at higher revs in all gears. That is likely to be valid for our motos, too. It could be a partial explanation of the inconsistent wear among splined shafts of the same vintage and usage.
Maybe somebody who has done this mod will post here. If
you work out the details and do it, please post the progress with photos and keep us informed of the outcome. If you contact the original poster and get an update, please let us know.
