Hello,  I just got a 1984 BMW K100RS 4 days ago and I wanted to do some routine maintenance/service since the bike was sitting in a garage for nearly 10 years prior to me getting it.  I started off with lubing the splines, however, when it came time to remove the swing arm for the final drive I couldn't.  I removed all four bolts, 2 were pretty rusted the others were in decent shape.  Based on the research I've done, most say you should be able to wiggle and shake the final drive and swing arm loose in order to separate them.  No such luck.  It's sealed pretty tightly and looks to be seized. I sprayed some PB blaster in the bolt holes and on and around the seam a bunch, let it sit then blasted it again.  I was able to get a little wiggle after that but barely any.  I cant fit a screwdriver in the seem in order to pry it open.  I ordered some Kroil to help cut through the rust, hopefully, that will do better than PB Blaster.  I took a rubber mallet to it but didn't want to hit it too hard in fear of damaging the final drive. 

Anyone experience this problem before?  Does anyone have any recommendations?  

Thanks!!

Since you never know what prior owners have done it is possible that somebody put some sort of adhesive or sealant on that surface.

Banging the final drive with a rubber mallet won't hurt it.

Another thing to try would be putting the bolts back in part way and tapping them with a hammer (within reason) to back the final drive off.

If you have a knife that you don't care about then you might try tapping that into the seam once you get a little opening.

could the po have run some sealant around the joint between the final drive and swing arm ?

don't forget here are 2 x locating dowels on the final drive that , if corroded could be adding some resistance to separation and movement

good luck

charlie99 wrote:don't forget here are 2 x locating dowels on the final drive that , if corroded could be adding some resistance to separation and movement

good luck

Good point. The final drive needs to come straight back to come off since those dowels won't allow for twisting.

Yeah give it a darn good flogging with a rubber hammer and make sure to catch it before it hits the floor.

I like Duck's suggestion to put the bolts back in and hammer on the heads.  Just make sure to have them almost all the way in.  A 1/16th inch of play is all you need.  A hardwood block and a heavy hammer should do the trick.

It might be wise to use four disposable bolts to prevent damage to the good ones.

Heat is yo friend.

If the final drive input shaft is seized to the driveshaft by corrosion, using wheel rotation snapped backward and forward several times to fracture the bond created by corrosion within the splines then pounding on the final drive with Thrash Metal vigor using a dead blow hammer might produce enough vibration to free it up.

Before you remove the final drive it's a good idea to drain the gear oil from it.  If you don't then you have to keep it upright to keep gear oil from leaking out of the breather hole at the top if you put it on its side.

Two Wheels Better wrote:Heat is yo friend.

Really? On a K bike?  Do you have asbestos knees? 

Thanks to all who have replied.  All great suggestions, I will exhaust them all until I get the damn thing separated.  Ill report back once I do to let you all know what did the trick.

Dowels can seize as said and IMHO that's the most likely cause of the problem. Heat first, then you could slacken the bolts very slightly, do them back up almost hand tight and do a slow ride on it to see if it will crack what is likely to be corrosion between dowels and the aluminium. Knife in there definitely wont separate it.

Will watch this one as its on my list for my new 83 K100RS.

Hi all, sorry for the delay but I was able to fix the problem.  I bought some "Kroil" and wiggled the swing arm and also whacked it with a rubber mallet until I was able to get some give and then I poured some kroil into the creases.  Rinsed and repeat.

Thanks for all your help!

Splines were in great shape btw

Well, there's good news!