1983 XJ750 rear end problem...

Mine does it too. I thought it was the clutch because when I felt,heard it it was just as the clutch plates about to lock up. Like it was loosing the last bit slip. Dissasembled the clutch and found the steels were all rusted up. Glass beaded them and got it back together. Haven't noticed it so far but I haven't gone for much of a ride. Also switched to motorcycle oil instead of car oil. Put new shocks on it too.I'll keep you posted.

 

That play is in the "dogs" that engage the gears and is normal.
The rest of the driveline "lash" is tiny by comparison.

 

I absolutely HATE the amount of slop in my drive line makes me sad, but that's one of the drawbacks to chain drive. I've learned to roll off and on the throttle carefully to minimize the jerkiness in town traffic.

 

Hey Brewster - have you checked your swingarm bearings?

My old Diversion had worn / dry bearings and it made the disconcerting noises you are describing. They are quite a small bearing for their application on the XJ's so they do tend to wear out quicker than conventional needle swingarm bearings.

 

I have thought about those shocks!! i think i may pull them off today and get them in a bench vice and see if i can tell if they are crappy. maybe the shock part with the oil damping is gone. cranking up the springs may make a difference.

 

I have looked at thoses swing arm bearings - they seam OK, but i haven't disassembled anything. just wedging a prybar up and down on them dosn't show any play - and the bike ride is good other than when i get on it. i'll look today and give them a shot of grease (I think there is a grease fitting??)

 

Hmmm i'll look into that middle gear damper. The book shows it, its a damper that would seam to make this kind of clunk if some higher (than what i normally apply) power were put into it. Also, the book makes a note of the fact that this middle gear runs in its own oil which while added by regular means through the main oil fill hole, to DRAIN that old oil there is a separate drain plug. I got this bike with 25,000 miles on it and no speedometer so im sure it's 25,000+. I have no idea if that oil was drained by the previous owner(s). I have drained that oil when i got the bike - but must confess that i have only drained it once in the 5,000 miles i have put on it. --- Sure sounds that this area of the driveline could be the "clunker"

 

I don't think there is a grease fitting - it's a take apart job on the shaft drive swingarms as there is no straight through pivot bolt, just tapered bearings on each side of the pivot point.

 

Brewster, don't mess with that middle drain plug, you could be heading for a world of hurt
Mr Time to Ride did a Mr Science on it not too long ago, there's not much in there and it seems those bolts like to strip
believe me that oil's not the problem

 

Not to bring up a dead thread, but did anyone have any luck figuring out what was going on? My '82 has been doing the same thing, but I can't recreate it with the bike on the stand. For me, it only happens when getting started rolling from a standstill, and not every time, either.

I have the normal (I think) amount of drivetrain play, but I don't think it's related. If it was, then it would be jerky every time I transitioned from decelerating to accelerating, wouldn't you think? This particular clunk only happens when it's under constant torque, after rolling about 5-10 feet, and only once. After that it won't happen again until I come to a complete stop, and then start up again.

I'll check the shocks, like Robert suggested, but I would think if they were the issue, I'd be feeling clunks all the time, not just under this one specific set of circumstances...

I've checked for play on everything I can see externally. I'm hoping someone else has already figured this one out, because I'm really not looking forward to opening up the drivetrain without even having a good idea what I need to do...

 

x2

 

I think I have the same noise in my new '82 Maxim. A little clunk when starting from a stop, even slipping the clutch and starting slowly, and doesn't happen all the time. When it does happen, it always feels like it's at about the same point as I release the clutch... when the handle is about 80% out.

 

Got anything in the trunk? I think my clunk comes from tools shifting in the tail section.