1992 BMW K75S - Drive Shaft Spline Lubrication

When I bought this bike in the spring it appeared to be very well maintained and that remains my opinion of its condition. But there were no service records, and the previous owner, who had owned it for less than two years, did not know when the drive shaft splines were last lubed. This is not a maintenance item to skip, so it was high on my to-do list. It was also a good time to replace the rear shock.
CORRECTION: While the splines on the U-joint end are in good shape, the ones at the final drive end are NOT. I have ordered a replacement drive shaft.
Helpful videos:
• 1992 BMW K75S - Drive ...
• BMW K75 K100 - Greasi...
The process I used:
docs.google.com/document/d/1s...
Shock absorber:
kpartsholland.com/products/ko...
00:00 Intro
00:10 Background
00:23 Research
00:55 Approach
01:17 Remove the rear wheel
03:39 Remove the rear brake caliper
04:19 Remove the rear shock absorber
05:21 Remove the final drive unit
08:49 Remove and lubricate the drive shaft
09:56 Reassembly
15:15 Outro

[@lee-dg9yh]

Thank you for your effort in producing your video on spline lubes Unfortunately, I must comment so others don’t get misled by some of the items in it. As others have told you, after you posted your video, your splines are indeed severely worn!!! The splines at the final drive end should have the same shape as the splines at the transmission end. Because the snap ring at the transmission end does not allow the shaft to slide in and out on that end, there will be virtually no wear at that end. Virtually all wear will be at the final drive end. If you look at the still photo of the splines on the final drive end of the shaft before you start the video, you will see that each tooth of the spline looks like a very pointy mountain with a very large distinct step on one side. The tooth SHOULD look like a very symmetrical mountain with an almost 1/16” wide flat top. Any lack of symmetry on both sides or narrowness of the flat top is all wear. The large step on the driven side of each tooth indicates a very worn shaft. The narrowness of the peak indicates very little mileage left before the shaft strips completely out. The lube you used, even though it is what is recommended by Clymers and iirc at one point by BMW, has proven over the past 38 years by people who have put many hundreds of thousands of miles on early Kbikes (especially the 20 spline driveshafts that came on the ‘86 and later non paralever bikes) to be sorely lacking in performance. Early Flying Bricks require a good high pressure (unlike Optimol) grease high in molybdenum disululfide (above 50%) preferably with some tacky additive like provided by Wurth 3000 to prevent washout. A highly recommended spline lube is sold by Ted Porter’s Beemer Shop. I also belive the spline lube sold by Euromotoelectrics is a suitable lube. The amount of wear on your shaft might (or may not) indicate similar wear on the final drive input splines. Best option is to buy very good used replacements with little wear. PM me if you are having trouble finding good replacements. Most of what I see on Ebay are as bad as what yours are, even though the sellers say they are fine. Buyer beware! Another tip for those watching your video, never allow the swing arm to sag much more than where the shock allows it to travel. The boot between the swingarm and transmission could be as old as 40 years old and brittle. Excessive droop could tear it, adding $56 (as of this date) to the cost of your spline lube. I see you did put a jackstand under the swingarm, but it was after you had already allowed it to go to full droop while disconnecting the shock. A few other tips, either place a 2x8 or 2x10-12 board under the centerstand (if you are strong enough to get it on the centerstand with the board in place) or roll the rear tire up on a 2x and then place another 2x under centerstand, put it up on centerstand, then remove board from under rear tire. You will then be able to fully remove rear tire without removing rear license plate section of rear fender. Or you could just remove the license plate section of the rear fender to get tire out. Another tip, do not remove the rear shock at either end. After the final drive is disconnected from the swingarm, just slide it back and pivot it 90 degrees and let the shock support it while you remove the driveshaft. Don’t remove the speed sensor, just disconnect it at the connector by the coolant overflow bottle. What ever the method, relube the splines AT LEAST at EVERY rear tire change!!! New driveshafts are currently $750 from BMW and will only go up before they will be No Longer Available (NLA). Re lubing and inspecting the splines is cheap!

[@JDnBeastlet]

lee - thank you for the information as I was unaware. I have updated the description and will republish the video with corrections soon.