85 K100 Final Drive Kaput!!! Upgrade everything?

[lukeman]

This weekend during a full throttle off the line start through second gear I come off the throttle and hear this terrible racket coming from below.  I still have thrust but whenever I decelerate or hold down the clutch it makes a terrible sound.  Like there are marbles rattling around somewhere.  I just swapped the tranny with a 23k K1100 one month ago, the clutch looked good, all the splines are fine.

Up on the stand everything is fine as long as the rear wheel isn’t spinning.  The noise is coming from the final drive I believe.  I figure if the drive shaft broke, I wouldn’t be able to go anywhere.  So I hobble my way 10 miles home hoping that at no point does the final just decide to lock up.   :dunno2:

I’ve heard that it is pretty rare for the final to go on the old K100s, but not impossible.  I’m going to rip the rear end off this weekend to check out for sure, but I have a ton of play in the rear wheel while in gear and all the sound comes from that location.

My question for everyone is does it make sense for me to bring everything up to a K1100 rear end spec?  I already have the k1100 transmission in which would be the hardest part.  Does the paralever make that much of a difference to justify the cost of swapping out everything as opposed to just the final drive? I assume that I’ll need to get a new shock which is the biggest cost of entry…

Drive shaft  ~$175
Swing-arm   ~$100
Rod              ~$40
Shock          ~$300-$400
Final Drive  ~$300

[Inge K.]

This one wasn`t exactly quiet either, but the bike (-85. RS) was still able to move in the correct direction.



Inge K.

[lukeman]

Damn...  That must have made a horrible noise.  I'll definitively inspect the drive shaft thoroughly as well!

[lukeman]

 Got ambitious today after work and well I think I found the culprit.



Oh and its pretty much a bitch to remove the front of the driveshaft from the transmission when the rear is missing.   :dunno2:

[frankenduck]

If you pull the swing arm off then you should be able to pop it off through the pivot hole with a big screwdriver.

I think I may have an 85 driveshaft in my stash.  I'll check in the morning.

[DRxBMW]

Got ambitious today after work and well I think I found the culprit.
Oh and its pretty much a bitch to remove the front of the driveshaft from the transmission when the rear is missing.   :dunno2:

Curiosity ?   did the U joint make any protest noises as a warning of impending doom ?

Tip: if you remove the swingarm, EASY beans to pull a stubborn DS. BTDT

[lukeman]

Thanks Duck,  I'd be interested if you had a decent splined 85 K drive shaft laying around.  If not I might just go Paralever, as this particular drive shaft is harder to find than the other years.

It didn't really make any noise that I was aware off, it wasn't notchy from what I remember.  Now that I think about it  I do remember seeing an o ring on floor when I pulled it out a month before it blew up.  It was in my dad's garage and figured it was there before I started removing everything..  Maybe not now though.  It was a real mess in the swing arm, the roller pins of the bearings went everywhere.

I did remove the swing arm as it would have been impossible to do with it on.  I'm not sure if every lock clip on the driveshaft was as tight as this, (probably, but i've always just banged it off with vice grips and a hammer) but I couldn't remove it tugging as hard as I could. I ended up having to do what Duck suggested by punching out one of the holes of the joint and then getting a heavy duty screwdriver through the swimg arm pivot hole,making a level using the tranny hole as the fulcrum.

[wmax351]

Just saying.

[frankenduck]

Spline pic emailed.

You left something off of your list: Right peg plate.  It needs to step out at the rear to clear the wider swing arm.

You have 3 options:

1) Shim out your existing one - possibly with longer mounting bolts.

2) Use one from a K100RS4V.  (You'd probably have to buy a new one for $165 because they crack easily if the bike is dropped on the right side so finding a used one is nearly impossible.)

3) Install K1100 peg plates - but that's a little more involved than just the peg plates because they mount differently.

See here: http://www.realoem.com/bmw/showparts.do?
model=0532&mospid=51713&btnr=46_0233&hg=46&fg=65

That's what I did on my K75 when I converted it to paralever:

[lukeman]

Oh yeah i didn't even think about needing a different peg plate.  With the 85 driveshaft in the mail I think i'll I'm going to leave it mono.  It would be tough to justify spending all that money to reduce the accel/decel motion of the rear wheel by half.