Hi all, having some issues with my 250 gripper in the gearbox department. The problem is a loud cracking noise from within the crankcases and temporary loss of drive for a split second.This only happens when the motor is under load (climbing a hill) there are no problems when the bike is on the flat. Originally thought it might be the cush drive but that is all working perfectly. Any advice gladly accepted thanks Higgo.

Sure sounds like a cush drive problem.

Any noise when the drive resumes?

No there's no noise when drive resumes, and like i said in my brief explanation the cush drive is working perfectly.

I did see you said there was no issue- but that sure sounds like it!

Did you check the woodruff key?

Primary chain?

I would think if the gear dogs or drum had an issue it would make a big sound when re-engaging.

Sorry- guess not much help!

I do have a 74 MAR gearbox on the shelf- but I'm afraid any pics wouldn't help much.

the ossa drives through a taper, behind the cush drive. pull it off and lap it back in with fine grinding paste. these tapers can a pig to get off,

but if your's is loose you could have it easy. pullers are available, don't bodge it!

 

changing the crank seal whilst in there would be sensible.

 the only woodruff key is in the fly wheel .

 

 

Dang-

Of course there is no woodruff key on the primary side.

I just had two of them apart to replace crank seals too!

Jeeshh!! (I'm an idiot! )

So I fully agree with Stan.

Pop it all apart and make sure all is good.

Chain, cluch, Cush etc.

I've split the crank cases and everything is good in there. Had my mate round as a fresh pair of eyes and he had another look at the cush drive. He inspected the gears that sit on the cush drive and found the facers where the 2 gears mesh together have high spots and of course they should be silky smooth?? Hopefully we're on to something.  

the cush drive faces are always rough.this will not cause lack of drive.even with a broken spring they cannot slip past each other.

 

  CHECK THE TAPER.

They can slip past each other if they aren't tightened fully, which can also happen on a MAR if the collet that retains and compresses the spring is sitting on top of the splines on the tapered sleeve instead of being seated in the splines, which means the spring isn't under enough tension. Can't remember the Gripper component arrangement exactly as it has the weight that the MAR doesn't.

 

I had a slipping cush drive on one of my bikes once, due to the above