1985 K100RS. A couple of maintenance items question.

I have a couple of questions for you long-time brick owners. I've just finished my 3rd riding season since owning it and have now put on 11,790 miles in that time for a total of 41,800 miles. I pulled the drive train out of it in January 2020 right after getting it, which included pulling the clutch assembly for checking the friction plate thickness and for any leaks. The friction plate thickness was measured with a micrometer at various locations and all were in the high 5.2xmm range. I am having no clutch issues and have no reason to suspect a seal leakage, so given what I have said, when would you guys have another look at the clutch? Oh, the splines on the gearbox input side were lubed with a bit of Staburags on reassembly but 2 years ago I went to TS60 on the output side splines. When I do go back into the clutch I'll use a little TS60 there as well.

Also, when would you guys ever drop the oil pan just to check for sludge buildup? FYI this past riding season was 5,000 miles, all on Mobil 1 15W-50 synthetic. Again, having no issues.

Thanks,
Tom

mcmlcccvrs said:

I have a couple of questions for you long-time brick owners. I've just finished my 3rd riding season since owning it and have now put on 11,790 miles in that time for a total of 41,800 miles. I pulled the drive train out of it in January 2020 right after getting it, which included pulling the clutch assembly for checking the friction plate thickness and for any leaks. The friction plate thickness was measured with a micrometer at various locations and all were in the high 5.2xmm range. I am having no clutch issues and have no reason to suspect a seal leakage, so given what I have said, when would you guys have another look at the clutch? Oh, the splines on the gearbox input side were lubed with a bit of Staburags on reassembly but 2 years ago I went to TS60 on the output side splines. When I do go back into the clutch I'll use a little TS60 there as well.

Also, when would you guys ever drop the oil pan just to check for sludge buildup? FYI this past riding season was 5,000 miles, all on Mobil 1 15W-50 synthetic. Again, having no issues.

Thanks,
Tom

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I would check the transmission input splines at 60,000 miles or so, OR if it ever gets a little wonky downshifting from 4 to 3 or 3 to 2, or next year sometime. I just don't trust Stabarugs to be as long a life lubricant as the TS 60.

Assuming modern (later than about 1980) oils I wouldn't even think about pulling the pan to look for sludge, ever. You can if you want, reach in with your finger and see what you find through the bottom plate when you change the oil filter. I would bet there is no sludge.

I do advise as a preventative measure adding CD2 Engine Detergent or Valve Medic in the oil about 200 miles before an oil change every 12,000 miles or once a year. This is to prevent the starter clutch pawls from sticking from varnish from the oil.

Thanks, Paul. I'll leave pulling the trans again for at least 2 years based on my current level of riding. I'll do the CD2/Valve Medic or equivalent the end of next riding seasons oil change.

Thanks,
Tom

Older K bike maintenance ideas

Paul is right about keeping the Sprag starter clutch pawls "fresh" and anything else he says. I put a new sprag in once. I had coast started it many times in 2nd gear before I really fixed it.

My '85K100RS with 204,000 miles likes to have the "microvolt/millivolt" connectors touched with a contact enhancing (cleaning) solution from time to time NAPA CE-1. Those 30 year old blade pinching connections need to be cleaned of corrosion or you may get very sudden on/off/on engine symptoms, start with the big connector over the battery. New parts, like the crank rotation sensor always give you 50% of a brand new of a pair of those microvolt connections, often enough to make the connector problem go away and all are left to think that it was the sensor.

When I put a 12 rivet Bull gear in (a first year K100 6 rivet goof) at 160,000 miles, I replaced the clutch friction disk for the first time, not because it was out of spec, just because. I grease both ends of the drive spline every 50,000 or so.

Learn to check the valves using shims when cold. You may rarely need to actually adjust them, shim and bucket.

Loved a '90K75S as well but sold it when a '13 R1200GS came home, kept the '85K100RS and a '03 KTM 250-4 EXC.

The engine seems to really love new spark plugs every 12,000 miles or so. It seems smoother afterwards.

Enjoy!

Can you put up a pic of your RS please, I wasn't to see how it differs from the R100 RS.

skibum69 said:

Can you put up a pic of your RS please, I wasn't to see how it differs from the R100 RS.

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They are about as different as..well, an airhead and a K-bike.

https://en.wikipedia.org/wiki/BMW_K100

Pic of my '85 K100RS during covid in NY state

Thanks, guys. Good information.