No drive!!!

[neo]

Ok, so I have had 2 x hard days at work and I mean real hard physical work, im dying to get out on the k... So I fill the tank and head off to my dads as its fathers day Sunday and he's going away for the weekend I figured I'd go and give him his bottle of wine and his card early. Start the bike (1991 k75 rt) on the button like clockwork as. Ormal despite the 115k miles under its belt, whilst riding I thought I could feel the teeth of a gear through the bike and it sounded a little noisier, then thought I was just paranoid and kept riding despite thinking this a few times, about 6 miles off so arrive at my dads blah blah blah then come to leave, ride off no prob about a mile up the road the noise of shredding gear and then no drive at all despite the gear, my suspicions it the driveshaft gear stripped or the rear bevel gear or both? Any ideas,tips, pointers, suggestions, help with diagnostics would be appreciated and for this I thank you all in advance 🍺

[frankenduck]

At 115k I'd guess it's the drive shaft/final drive splines.  Best way to tell for sure is to take the final drive off and inspect the splines.

[neo]

That will be my next move, is it clearly visable if they are gone? I believe it's just 4 bolts holding the rear assembly on, will I need to remove the brake caliper or drain any oil? Thanks again

[frankenduck]

Yes, it will be very obvious if they are gone.

Yes, on removing the caliper. You need to remove the wheel and undo the nut on the shock stud too.

You don't HAVE to drain it but if you don't then you'll need to keep it upright so that gear oil doesn't come out of the breather cap on the top.

[neo]

Hi all, update on the brick... ok so stripped the old girl down today to find:

Final drive

Worn splines on the drive shaft/Recon drive shaft ordered
Gearbox Removed to find: The center of the clutch friction plate (spline part) sheared from the actual plate itself!!
so when in gear the center of the friction plate (spline part) spins but the friction plate stays put!!! never ever seen this before, its completely ripped away from the plate itself, the previous owner had a clutch installed one can only assume not very well!!, my suspicions are that the friction plate was installed off center thus an oblique effect when spinning hence fatiguing the metal around the spline part of the friction plate causing a crack and eventually complete shearing off.

any suggestions whilst its all out? i have ordered the white grease from the bm specialist, a new plate, some washers i am told i need etc, do i grease the spline that goes fom the clutch to the gearbox? my guess is no because of fling off and contamination of the friction plate, please correct me if im wrong, i will grease both drive shaft ends for sure

thanks in advance

[frankenduck]

the friction plate was installed off center

The friction plate is loose when you pull the clutch in and would center itself.  And if it were installed off center then you'd never be able to get the transmission back on.

Are you certain that it is a BMW clutch plate?  Maybe they used something aftermarket.  Or it was just a bad clutch plate. :dunno

BMW clutch plate:

You can put as much lube on the splines as you want.  Just make sure that you only put it on the trans input splines and that there isn't any on the front of the trans input shaft.  Any that gets pushed out of the rear will be pushed out past the collar on the clutch plate and spin harmlessly off onto the wall of the bellhousing.

[neo]

Oh i see, so the plate is essentially "floating on the shaft" blimey.. something weird has happened with mine, lovely clear pics, many thanks, the friction plate looks slightly off center in the assembly tho, the clutch was a German made SACHS? i wisg i had taken a pic of it, i will do so and post them, the spline part has ripped away from the plate!! just outside the 8x studs in your picture, boy i hope the twit has re assembled the clutch correctly from stock, there was no grease at all around the splines on the gearbox/clutch end and seeing as it had just been replaced not good!! also a lot of bolts were loose in the process of the removal starting with the rear wheel!!! i just dont know what could have caused this, also the clutch splines look shite, quite pointed, again not good for a new clutch, the gearbox to clutch spline looks passable but it has covered 115k

[Inge K.]

the clutch was a German made SACHS?

Same company which delivers the genuine clutches.

Inge K.