Took the bike for a ride last night - Parked to enjoy the sunset and when I got back on the bike it wouldn't move.

When I let the clutch out and give it gas the bike begins to accelerate and then stops accelerating no matter how much more gas I give it.

When I let off the gas completely it just idles as if it's in neutral.

Does anyone have experience with this type of problem?

It's a 1985 K100rs

Thanks so much

Does the engine RPM increase but the road speed remains the same or does the RPM stay the same?

The clutch doesn't usually just let go but sounding that way,Any free play on clutch lever at all

RPM's DO Increase when I give gas

tjh1985 wrote:RPM's DO Increase when I give gas

See #3

@moriarti

There is little to no play in clutch cable - not sure how to adjust it to loosen it up

OK,disconnect clutch cable at gearbox end and then push clutch activation arm in and make sure it not partially sized and moves in and out easily.Any sign of stiffness then it must be serviced.youtube videos on clutch cable setting easy to follow


With cable OFF PULL CLUTCH ARM right back put bike in gear and push back/forth
to see if clutch is holding,fingers crossed

Well, shoot - Clutch activation isn't stiff and I tipped the bike over to boot. So no winning for me today. On to the trailer and into the shop it goes...Thanks for trying to help me figure it out though.

Thomas

This won't be the answer on your bike because the exhaust system is different.
On a 1992 K100rs I had sudden and complete lose of the clutch. I had been driving on a freshly seal coated road. You know where they spry down tar and them cover it with 3/8" minus gravel.
Anyway the engine was no longer connected to the rear wheel and the clutch lever was a bit floppy.
There ended up being a a small perfectly shaped rock held inplace with a bit of tar wedged between the clutch arm and the exhaust system. So hard to see anything in there on the latter bikes with the bulge in the exhaust system.
 I am guessing a seized needle bear in there might act the same. Hard to imagine it just seizing up solid though.


I hope yours proves to be as simple.

Is the final drive making any awful noises..?

gorio wrote:.......
There ended up being a a small perfectly shaped rock held inplace with a bit of tar wedged between the clutch arm and the exhaust system. So hard to see anything in there on the latter bikes with the bulge in the exhaust system.
......

I've heard of this happening before. We had someone here a few years ago that reported a stone had lodge in there preventing the clutch arm from fully returning.

The 1985 K bikes the clutch friction disc hub and input shaft on the transmission were supposed to be lubed every 15000 kilometres if I remember correctly.
My 85 K100RT had the transmission pulled and the splines lubed before I bought it at 16000 kilometres I pulled the transmission and lubed the
splines again at 30000 kilometres. I also installed a newer friction disc in the clutch. The hub on the new disc looked like stainless steel the
original was dark metal. Apparently BMW changed the material in the hub and input shaft and the lube interval changed to 45000 kilometres.
Again going from memory. If the splines are not lubed they can wear away and stop driving.The splines on both ends of the drive shaft are
supposed to be lubed as well.

Hi,did you get to the bottom of the problem, as I have now a similar issue.

First question, its there any mechanical noise or grinding? OP never responded to that question. Put bike on centre stand, run it in gear check that out.

Second question, any oil dripping from the hole in the bottom of the bell housing??

Third question, is there free play at the clutch lever?

On my problem bike started loosing drive, as though it was running out of fuel and there was some mechanical noise and straight away I thought of the splines, reduced throttle and bike would drive but as soon as I increased revs same problem, felt lucky to get home, noticed on a downhill section of road bike picked up ok so then started thinking it could be the clutch,I have just recently bought the bike (1985 K100RS) so don’t know the maintenance history but was planning to lube the transmission and gearbox splines so this has just brought this forward. When I bought the bike seemed to be running fine ,carried out a service and found air filter in wrong way around,incorrect spark plugs, oil breather pipe badly split, corrected all these things and bike now runs worse than when I bought it, very disillusioned with bike at present.

I'm with olaf#14,then remove drive/prop shaft to  inspect splines/joint and run the bike to see if noise persits before doing a full stripdown,best of luck

Thank you all for the advice it is appreciated,

Middleton wrote:On my problem bike started loosing drive, . . .

Have you checked the clutch adjustment according to how it is explained in BMW's manual?

Hi, Clutch adjustment seems fine,bike runs through the gears when on the centre stand, gear change seems smooth but there is some clunk what I think is from the driveshaft when the clutch is released but as I have never had a shaft drive bike before I am not sure whether this is normal or not, that noise wasn’t noticeable when driving on the road. There is no oil from the gearbox hole.
I have just noticed the rear brake disc appears to have several large fractures to add to my woes so I don’t want to ride it until that is fixed, it was quite a eye opener when I saw them and now feel quite lucky that I actually got the bike home.

Middleton wrote:Hi, Clutch adjustment seems fine,bike runs through the gears when on the centre stand, gear change seems smooth but there is some clunk

That would be a No answer to my question. 

It's likely that drive splines are a problem but a clutch adjustment isn't checked the way you have described.

On the clutch adjustment, I checked the distance against the cyber manual and it was ok, the clutch action is quite light but was not sure on the free play,when I touch the clutch at the handlebars you can see slight movement at the clutch cable at the gearbox end but it does not seem to operate the clutch just a bit of play, I am not sure if the allowed 5mm of free play at the handlebars should move the clutch arm at all.

Middleton wrote:On the clutch adjustment, I checked the distance against the cyber manual and it was ok, . . . 

I am not sure if the allowed 5mm of free play at the handlebars should move the clutch arm at all.

Which distance is ok?

Free play is the distance the clutch hand lever moves before its cable moves the clutch lever that is lightly contacting the clutch rod piston. Free play is measured at the gap created between the clutch hand lever and the clutch hand lever housing.

I measured the 3 inches at the actuating arm where the rubber gaiter is.

I think from your description I will need to alter the free play slightly as mine as soon as you touch the clutch at the handlebars you can see very slight movement at the clutch actuating rod.

UPDATE:

All six bolts on my Output Shaft were sheared off (pics attached). Hence why the motor was spinning and I wasn’t going anywhere.

I’m replacing the 6-bolt (pictured) with the K1200 12-bolt (pictured). And as one would expect, the deeper the project goes into the engine the more issues pop up...new water pump on order now. But I’m good with it all because this baby is going to running AMAZING in another few days!

Thanks for everyone’s input when the problem arose. It’s pretty awesome to have a community like this one hear.

You say pics attached but I'm not seeing any mechanical gore

@middelton - yes, I did. The bolts holding the output shaft sheared off. I have a more detailed update with pics

Lovely pics, how very weird that they finally let go when the bike was at home! Do you usually set off by doing a wheelie down the street?

Hello tjh , are they bolts or rivets ? , the factory unit is originally put together with rivets , if they are bolts someone has perhaps been in there and not used the correct fastener ?

John Re

Melbourne Australia