'87 R80RT - jumpy in first gear

[Manfred]

I've been riding this bike for 8 or 9 years. Today abnormal stuff. In first gear, 5,000 rpm or so, funny noise (box of gravel?) and bike acts like it's jumping in and out gear. Doesn't not happen in other gears. At work, so not much time at the moment to dig into it.

[Bamboo812]

I'd drop the oil and look for chunks on the drain plug...

[Manfred]

I will ride it home gently after work and do that before riding it again.

For the record: I have an hydraulic oil pressure gage installed and the warm/hot pressure at 3,500 and up is 80 psi. Has been around that since I installed the gage.

[Kurt in S.A.]

You're measuring engine oil pressure at 3500 RPMs? Nothing to do with the transmission oil, though.

Kurt in S.A.

[Manfred]

Right, Kurt. Oil pressure starts off in the morning around 100 psi and drops to 60 or 70 at idle when hot. Runs around 80 psi at operational engine speeds.

[Manfred]

I adjusted the clutch at the handlebar as there was no play in the handle. The transmission oil was down a little, so I filled it up.

Here's what's interesting: when the bike is running in neutral and the clutch handle is not engaged, I can run up the throttle to 3,500 rpm and it sounds fine. When I pull in the clutch handle, it sounds like robust baby rattler from the area where the clutch engages.

Weird enough for me. Any ideas?

[Kurt in S.A.]

Clutch throw out bearing? In the first scenario, the bearing wouldn't be turning; in the second situation, it would be turning.

Kurt in S.A.

[Manfred]

My Clymer manual shows a thrust bearing around the push rod of the clutch. Would this be the same as a throw-out bearing? I find no mention of that.

[Bamboo812]

Same same. There needs to be free play in the cable, or the thrust bearing will get fried. If it's not already...

[Airbear]

My Clymer manual shows a thrust bearing around the push rod of the clutch. Would this be the same as a throw-out bearing? I find no mention of that.

Yes, thrust and throw-out refers to the same function. You can access that bearing with the gearbox in the bike by removing the clutch actuating lever at the rear of the box. Draining the gearbox and examining the sludge on the magnetic plug would be the first step, however.

And before Duane gets grumpy again you'd better check this web page: http://w6rec.com/duane/bmw/trans/