I am rebuilding my 1992 K100RS after a run in with a cager.  One of the damaged parts that needed replacement was the paralever swing arm. 

Now that it is all assembled I noticed that with the bike on the centerstand the driveshaft's u-joint rubs on the inside of the swingarm. 

I have checked the shaft and it is true with no run out, and the u-joint is smooth with no play or binding.  The swingarm is installed correctly with proper preload and no play in the bearings and the driveshaft is installed with the snap ring correctly in the groove in the transmission output shaft.  The only way I could get rid of the rubbing was by shortening the new YSS shock by about 8mm to rise the swingarm.

Has anyone else seen a similar situation?  Is there anything else I should check?

Point-Seven-five wrote:
Now that it is all assembled I noticed that with the bike on the centerstand the driveshaft's u-joint rubs on the inside of the swingarm. 

Which one of the u-joints?
If the rearmost u-joint, is the circlip between the drive shaft
and the final drive shaft correctly mounted?

Inge, it appears to be the front u-joint since I can feel the resistance when turning the drive shaft with the final drive removed.

It appears that the circlip is in the proper location in the spline connection to the transmission output shaft.  The end of the shaft just reaches that support in the swing arm and there is only a couple mm. of end play on the shaft.

The bike was rear-ended in a collision last fall which broke the swing arm just in front of the joint where the final drive is attached.  The u-joint at the final drive is good with smooth movement though it's entire range of motion.

Point-Seven-five wrote:  Is there anything else I should check?

You didn't mention that the u-joints were correctly in phase. Could that cause the rub?

U-joints out of phase would cause vibrations, here it sounds like something
is out of normal position.

Have you checked the svingarm mounts in the gearbox?
What I have in mind is that the sidewalls in the gearbox maybe have been
deformed and moved slightly to one side....that would move the swingarm
out of position relative to the driveshaft.

Laitch wrote:

Point-Seven-five wrote:  Is there anything else I should check?

You didn't mention that the u-joints were correctly in phase. Could that cause the rub?

U-joints are phased.  It's an automatic thing I do with them so I didn't think to mention it.

I suppose the output shaft from the transmission could be bent, but I can't see how it could be bent by a force applied to the drive shaft when there is a u-joint between the application of force and the shaft, and the joint and the shaft have no visible damage. 

I guess that I might have to take the time to check output shaft runout.  Won't happen for week or so.

Just curious but how do you know/make sure your u-joints are phased?  (this is for me to get it right, not you .75)

If you have only a 85 K100RT then you don't need to know as only the 16v engines have 2 uni joints.

How do I phase my u-joints?

I have red paint marks on the two halves of the drive shaft that I made by phasing the joints on the bench and then marking the points that need to be lined up.

Thank you gentlemen.  While I don't have a Paralever now, I think there is every possibility that I will get one eventually    I will have to say that every time I think I hear something low down towards the rear I think that it is some or all of my rear splines going to pieces.  By the weekend I hope to have the transmission off and have a good look at everything.  When I did my FD splines last year I know that phasing wasn't on my radar.  Glad to know that this is one step that I didn't inadvertently screw up.

And back to the real issue at hand....

Point-Seven-five wrote:

Laitch wrote:

Point-Seven-five wrote:  Is there anything else I should check?

You didn't mention that the u-joints were correctly in phase. Could that cause the rub?

U-joints are phased.  It's an automatic thing I do with them so I didn't think to mention it.

I suppose the output shaft from the transmission could be bent, but I can't see how it could be bent by a force applied to the drive shaft when there is a u-joint between the application of force and the shaft, and the joint and the shaft have no visible damage. 

I guess that I might have to take the time to check output shaft runout.  Won't happen for week or so.

Have made sure the back uni is clipped into place like the front one goes in because if not they work their way forward then go out of balance in a big way and usually tear the shaft and drive housing to bits.

Both ends of the drive shaft are firmly clipped into position.  The front has a tiny bit of end play, less than a mm, and the rear has almost none.

perhaps could be worthwhile removing the swing arm and just seeing where in fact its touching

but I thought I read that its when the rear end is at full extension on the new to you shock ?

to me it kinda sounds like the g/box shaft end of the drive shaft hasn't been fitted home fully to the g/box , letting the knuckle of the uni joint sit out further than normal ?'
but you checked that ...

another thought .what is the distance eye to eye of the new rear shock  , is it close to spec ?

Charlie, I measured the original length on the new YSS shock at 15" eye to eye.  By shortening it about 8mm I now have it so the drive shaft doesn't rub at full extension.  I'm not sure what the specification is for the length of the rear shock.

.75,
Is it possible that the transmission housing got damaged (where swing arm pivots are) from the collision?

BTW I will be in Jamestown NY Sunday and have some spare parts (transmission) if you are interested or in need.

Caveman, I don't think there is any distortion of the mounting points on the transmission.  There is no cracking in the metal around the points where the swing arm attaches, and the pivot pins are "easy" to insert into the swing arm bearings.

I appreciate your offer, but until I check the output shaft for runout I will hold off buying any more parts.

.75
The stuff I have can be got for a coffee and tip on some good roads in your area. I bought 3 basket cases (85 100rt, 86 100rt, and 92 1100lt) all in one box to fix up my other bikes. I don't like the hassle of trying to sell the stuff over the net and shipping it out. If I have something someone can use or need close to me they are welcome to it.

Caveman, thanks for the offer, but I would rather confirm the need for a transmission since I am also trying to get out from under a pile of spares cluttering up the garage. 

I still wouldn't mind meeting up for a coffee and to trade info on good roads.  I know there's a lot of them around your parts.  I used to ride enduros back in the 70's in Meadeville, Grove City, and Oil City to name a few.