Now that parts for round one repairs are arriving and being installed I've been looking at round two, which is a rattle only when cold. I put this down to the cam chain tensioner, it sounds like chains, but searches seem to show a possible rivet issue and when 12 rivet output shafts first appeared is a bit ambiguous. I thought 86.

Without looking inside, can I otherwise tell if this 05/86 R100RS has 6 or 12 rivets on the output shaft?

I've also read if the rivets have an issue and the gearbox is out, as it is, you can feel slop in the output shaft. Tried that and can't feel any so I'm hoping I can rule that one out.

The 12 rivit shafts first appeared with the introduction of the 16v engine and then slowly made their way into the remaining 8v which were in the RT and LT and then were not in any great numbers. I took the crank cover of a 91 LT and it had a 6 rivit shaft but I have a 5/90 engine here with a 12 rivit shaft so except for the sure knollege that if its a 16v it will have one its a lucky dip but nothing before the 16v engines had a 12 rivit shaft.

Oh dear, I'll have a look when I do round two. thanks.

I've had a look inside and if these are the rivets in the pic, then I have 6 and they are solid

That's the critter. Many early Ks go all their life without failure but I have heard of failures as early as 30000k and up to 400000k before expiry.

Hey, Robin.

Is that the output shaft see from the right side cover? 

Incidentally, how does one go about replacing it? Does the gear box / bell housing have to come off?

Erman wrote:Hey, Robin.

Is that the output shaft see from the right side cover? 

Incidentally, how does one go about replacing it? Does the gear box / bell housing have to come off?

Gearbox and bell housing and sump have to come off as well as the oil/water pump.
It's quite a big job as jobs go on a bike but can be done with the engine still in the frame.

Yes the right side cover was off. Those out of focus nuts are on the crankshaft.

Here's a BMW Service Document on getting the output shaft out with the engine in the frame to resolve the knocking when cold issue.

[url=http://starshed.net/K100RS/11 037 88 (2289)r output shaft.pdf]http://starshed.net/K100RS/11%20037%2088%20(2289)r%20output%20shaft.pdf[/url]

Obviously they would have a bike lift to do it, I don't and I don't think I'd try it unless the engine was out of the bike and on the bench.

There seems to be a bit of an issue pasting a URL.

unfortunately ...you have to go in really deep ....

Thanks for the input. 
As I understand the bike is still rideable with that clacking noise, meaning I can take it from home to the workshop 5 miles away?

I would recon so ...mines has be clacking away for at least the last 50,000 k s

You are certainly in the correct area. The noise is usually not caused by the loose rivets.
The noise is caused by a defective tensioner spring assy on the thin gear that's mounted on the rear of the output shaft main gear.
The retaining pin that holds the annular tension spring to the back of the main gear is likely worn out or sheared off and the annular spring end is also worn out where it mounts on that retaining pin.

The annular spring is designed to rotate the rear portion of that shaft  (tandem )gear assy so the gear teeth are slightly misaligned when installing. The installer has to load the spring so the gear teeth of both front and rear gears are in alignment and then engage the gear assy back into mesh with the drive gear on the crank. The mesh between the two main gears then has "pre-load" and has 0 "lash" between the teeth. When the spring has failed as they all do, the gears clatter against each other when cold.......as things warm up, the clatter dissipates as the gears expand.
 In addition to the box of rocks syndrome, the engine will also exhibit a disturbing heavy "growling" noise when cold & abruptly closing the throttle to slow for an intersection. Even more pronounced if the early TPS is active. That noise sounds even more like it comes from the chain area.
 There is a bmw bulletin on correcting it and I believe they change the design of the spring as well as change the thrust washer behind the gear from a tension waved washer to a selective spacer washer.
 It's such a PIA that most don't attempt it unless there's a failure.
A qualified BMW mechanic with experience and all the shop tools could complete the job in about 4 - 6 hours.

Regards, Ibj...

I  read a post on another forum where the knocking when cold problem was solved by reshimming those cogs. 
There are shims in front of them and adjusting them correctly solved the problem.
The premise there was that the cogs bang against each other.

I think the re-shim you are talking about is the replacement of the washer I mentioned between the gear & the rear bearing with a measured to size selective shim.
 I'm not 100% sure. It would still require the previously mentioned removal of the shaft.
Regards, Ibj...

Part 19 on this image is the shim.

Sorry ijm, I dunno where that is your talking about, but adjusting that shim (19), and the book settings are wrong, will certainly stop the cogs smacking together.

Robin,
 We are on the exact same page. You and I agree that the shim is (at least part) of the recommended bulletin.
Not only does that shim need to be installed (Have to measure and obtain the correct one), but it actually replaces (supersedes) an original curved thrust washer.
That shim is part of the fix, the replacement of the round spring Part #17 and the dowel pin that secures it (not shown) and replacement of parts #13 are also required.
Sorry my original wording was so confusing.
Regards & good luck, Ibj....

For me, It really is a big job. I'll put up with the knocking noises when cold
Since I tuned the TB's the noises have got a lot quieter

Great choice, Robin. I am of the same opinion with mine.

Frankly, if I were to have a major engine failure say from a broken timing chain, I would probably replace the entire engine with a used one rather than trying to fix it.
 Used K100 engines (especially 8V) can be bought all day on Craigslist for $150.

I might, however consider doing the shaft update on the used engine while I had it out on the bench.

Picking up my new (old) R100rs next week. Wish me luck, I bought it sight unseen!

Regards, Ibj...

I got an R1100RS in the garage in bits. Talk about torque, I'm sure my arms are 2" longer just riding it home. 100Kms (60 MPH) @ 2000RPM's

Honking big twin, thump thump thump

Hope it gets you home Jay. You'll love it .. thump thump thump.

Think of it like a ww1 airplane ....

In my earlier life.......say 20 years or so ago, I had an 81rs (same color) and I've always wished I could have it back. After that Rrs was crashed, I then had an 85 Krs.....just like the one I'm riding now.

Since obtaining this one......it's never been as wonderful as I remember the first one being.

I'm hoping that the 82 Rrs is indeed every bit as wonderful as my memories of my first one were.

I had an opportunity yesterday to ride a 1996 R1100RT,  the owner & I were considering a trade.......his 1996 R1100RT for my 85 K100rs. 

I think I could have made the trade, however, I suspect he was trying to unload his perhaps because he learned at his last dealer service that there could have been oil in the area of the clutch (He says not) but the dealer gave him a $1700 estimate for a clutch job.

Also......the bike smelled fairly strongly of Hot motor oil.

I know it's an oilhead, but I don't think the rider should smell it unless it were leaking somewhere.

Test ride, however was quite impressive........was going very fast before I realized it.

The driver's seat though, seemed to not allow me to move far enough to the rear