I was checking-over my bike yesterday. I grabbed the rear wheel at 12 and 6 and push/pulled, and then at 9 and 3. I felt a little play and I could hear a faint "clunking". At 42,600 miles it looks like it's time for the final drive bearing to be replaced? No leaks. Drained the oil and there was absolutely no metal filings at all on the drain plug magnet.

I found this post from 10 years ago:

https://www.k100-forum.com/t5697-how-to-check-and-replace-the-final-drive-crown-wheel-bearing-and-seal

These guys did it with the final drive still on the bike and just pulled the cover. It seems straight forward enough, or.............

My BMW guru friend who used to work for BMW did mine, one on RT at about 80k miles, one on K1100 at about 100k miles. The K1100 was absolutley fine, came back from France, not a hint of a problem and stopped at a supermarket 2km from home and all was good, not a hint of play or wear or uneven handling. In the last 2km the race broke up and took out the seal. It was sudden. I rode it another 12km to his place a week later where the job got done. 

He always did them on the bike if he could, over time did many final drives.

Big thing is getting shimming right at the end of the job and he reckoned it was easier on the bike.

Yours seems to be failing early. He did warn me failure can be sudden and I keep thinking if the K1100 had failed like that on the motorway in France and the bearing itself had broken up.....

In my experience (two of them) you get a small amount of play if held at 12 and 6 but nothing at 9 and 3. Does yours clunk in all directions?

They normally last around 75K miles but you never know what kind of abuse they've had in the past.

Having done one I would say it is far from straight forward, I consider it more an engineering job than a mechanics job. The heating, the press required to get the bearing off (I refuse to believe anyone can just lever them off) and the shimming with a dial gauge is all much more specialist than I was set up for as a home mechanic.

An update. I spoke to an independent BMW service shop in town about my issue. He wants me to swing by tomorrow morning, put it up on the center stand, and he'll do an assessment. He has done them before. If he thinks it warrants servicing, then I'll pull the final drive and take it to him.

In the link I posted, the guy mentions that shimming only needs to be done if the housing is changed, but not if just replacing the bearing. Okay. I don't know what I don't know, but the guy I'm having look at my bike says it most certainly should be checked after replacing the bearing.

I can say for absolute certain that if I replace the main bearing in the bevel drive on one of my Guzzis, I have to reshim the crown wheel to ensure the correct clearance from the housing and then reshim the pinion to ensure that the crown and pinion are meshing correctly. I've done a few and it's a RRPITA - it can take a couple of hours if all goes well and the best part of a day if it doesn't.

I had to re-shim despite using the same housing and crown wheel, all I did was change the bearing but it must have settled on a slightly different part of the CW. Also read a lot about not having to re-shim. Seemed a lie to me!

I am curious as to the amount of change in the shim thickness with the new bearing.

It seems to me that except for wear on the gear faces, the manufacturing tolerances of the bearings would allow direct replacement without the need to make significant changes in shim thickness.  Or is that wear on the faces the cause of the bearing failure in the first place, thus requiring re-shimming of the drive?  Not being a mechanical engineer, I am ignorant on this topic.

Point-Seven-five wrote:It seems to me that except for wear on the gear faces, the manufacturing tolerances of the bearings would allow direct replacement without the need to make significant changes in shim thickness.

Unfortunately not. Bearing tolerances and case fretting usually add up to a new shim or two. As little as 0.25mm on Guzzi drives, but all the same...

I am just getting ready to go see the guy now. I suspect it might turn out to be a waste of our time, though. 

When I checked the bike and found that tiny, tiny amount of play, it was with the bike cooled down. It had probably been sitting for 2 to 3 hours.

I just came back from a brief ride for brekkie with friends, and with everything up to temperature there is zero play. I don’t get any movement in the slightest. Nevertheless, I am going to go see the mechanic.

As I suspected, a waste of time. With everything up to operating temperature there was no movement to be had. He just said to keep an eye on it. Okay.

He has a 1985 K100RS for sale in his shop on consignment with 81,159 km on it, so we checked that bike for play. It had considerably more play than my bike-clunking in every direction. I'm thinking maybe that bike needs to be looked at.

I have limited experience on these bikes and only one other to compare it to-the one in the shop for sale. I'm not going to worry about this and just ride the bike. Maybe I'll get the roller bearing and seal on my next parts order and have it handy.

WHAT!!!! And you didn't buy the bike - !

Dai wrote:WHAT!!!! And you didn't buy the bike - !

Nope. I need 2 bikes like I need another hole in my head. That and the fact that I have only been mildly successful at cloning sheep.

RS Rider wrote:

Dai wrote:WHAT!!!! And you didn't buy the bike - !

Nope. I need 2 bikes like I need another hole in my head. That and the fact that I have only been mildly successful at cloning sheep.

I agree about 2 bikes.

Seriously, only 2 bikes? How can you walk past a K like that?

The shims preload the bearing sideways by 0.5mm (or something like that, I'm going by memory) so it should really be solid at all temperatures. Sometimes it takes a bit of wiggling to squeeze the oil out so you can then feel the movement/clunking properly.

However, since yours also has movement when held at 3 and 9 o' clock, it may well be something else. Is the final drive fully tightened on to the swingarm??