Boxerworks.com

This was a non running project bike and I am sorting thru all issues that I find. I have got the engine running and have taken the bike around the block (Transmission, Clutch, Brakes are working).

I am currently changing both front and rear tires. The R100RT is on it's center stand with front fork legs on the ground. After a couple of days in that position, I noticed a few drips of oil under the final drive housing. After cleaning up the spline area and the final drive, after a couple more days, there is a visible amount of oil on the inside of the spline (under the yellow paint in the picture).
I did not see any leakage when the bike was level and both wheels on, could the tilt because of both wheels being removed cause this oil to appear?

I haven't checked the final drive oil level, would this occur if the final drive is overfilled?

Is it the main final drive seal (which would be strange because the seal is on the outside of the spline area) ?

Is it another seal within the final drive hub?

If there is minimal leakage and I monitor the final drive oil level, can I ride now and take care of this problem over the winter months (I live in Wisconsin)?

All comments would be appreciated, Thanks[

gsm_r100rt wrote: ↑Tue Aug 12, 2025 12:57 pm Is it another seal within the final drive hub?

Yes

#2 is a seal. pn 33 12 3 004 337 newer alt part # Shaft seal ( 30.42.7 )
#3 is a needle bearing pn 33 12 1 242 739 NEEDLE BEARING - 32X47X24.5
#4 pn 33 12 1 230 527 COMPRESSION RING - 1,8MM


#3 is a seal 33 12 1 233 528 SHAFT SEAL - 65X85X10

How tough would it be to replace those two seals?

Would it require any special tools?

I think it's almost certain to be the inner drive seal, the smaller one that locates in the main casing (#3 on the upper of the two diagrams posted above). Unusual, it's normally the big one that goes first. Replacing them is not too hard and, since you aren't disturbing the pinion or replacing running parts, you should get away without adjusting the backlash. Worth checking it before you start though.

The only 'unusual' (rather than special) tools you need are a couple of longish bolts... 6mm if memory serves. There are two threaded holes in the inner cover. Two suitable bolts will enable you to draw off the cover with the minimum of fuss. Best if the bolts have rounded ends where they will press against the outer cover.

Rob

gsm_r100rt wrote: ↑Wed Aug 13, 2025 12:53 am How tough would it be to replace those two seals?

Would it require any special tools?

There are a few YT videos.

https://youtu.be/ra4dSZv5Nfc?si=q8K_5gI8CYJsHlLb
https://youtu.be/DtI5Seo8usU?si=3OYu21Hs5q0qLwls
https://youtu.be/SdadynFQu50?si=4irbIoQqLLIfZsST