K100 maintenance advice - output shaft

[jetpoweredmonkey]

I'm stripping down my 1987 K100RS for some TLC.  The fuel pressure regulator seems to have gone south by leaking fuel into the vacuum hose and diluting the oil, so I need to swap that out, check the valves, do the splines and figured I'd give it a good once over with new injector o-rings, fuel hoses, etc. while she's in bits.

I really love this bike and it's in great condition, so I'd like to also fix the rattly output shaft.  I already changed the alternator monkey nuts and this did not cure the rattle, it seems very clear to me that the output shaft is the problem - a pretty good rattle when cold, goes away mostly once warmed up, but you can hear it a bit getting on/off the throttle.  It's not the cam chain.  Reading through the manual, it looks like a lot of work to get the shaft out, but it's also pretty straightforward. 

My question for the gurus is whether it's worth all the effort to replace the split gear spring, or is the rattle likely to come right back in another few thousand miles?  Or, is it possible to swap the output shaft for a later one from a 16V bike, with a possibly better design?

Thanks guys for any advice.

[Rick G]

The output shafts on the K100 from about 89 on have a shaft with 12 rivits and not 6 as yours does. The 6 rivit shafts were not strong enough and after about 100,000miles or so gave out.  There are a few who have tried to replace the rivits with bolts and extra rivits but they don't seem to be successful.
My advice is to get a 12 rivit shaft from a late model K100 engine and use it.  But be carefull if you buy a complete engine, I have seen 2 engines recently one a 90 the other 91 and both had 6 rivit shafts. They had either been robbed out or never had them in the first place.
I don't know for sure if a shaft from a 16v engine fits as BMW are in the habit of making changes at any time during a model.  A K75 is not the same and cany be used.

[TimTyler]

The fuel pressure regulator seems to have gone south by leaking fuel into the vacuum hose and diluting the oil,

How do you know? (Just curious)

... so I'd like to also fix the rattly output shaft.

How are your valve clearances, and are your throttle bodies balanced?

[jetpoweredmonkey]

Thanks guys for the replies.

As for the FPR going bad - I noticed last time I did an oil change that the oil level slowly climbed from halfway up the sight glass to past full after a few weeks of riding.  In addition, the oil became dark fairly quickly.  Somewhere I read about the pressure regulator failing and allowing raw fuel to be sucked into the #4 intake vacuum port.  I checked mine and sure enough, the vacuum hose was full of a small amount of liquid gas and has become soft and "sticky" as they do when exposed to fuel.  It wasn't enough to noticeably affect fuel economy and the engine runs normally, but it's clear that at least some gas is making its way into that hose.

Tim you are probably right about checking the valves and TB balance, I am certain that at least the TBs are probably long overdue for attention.  I suppose it's possible that getting things tuned up will make the rattle go away, just thought I'd check in for people's experience with that while I had the bike pretty well torn apart.  On the other hand, the bike runs like a dream and has a rock steady idle already.  It sounds like finding a 12 rivet output shaft is a bit of a crap shoot, so maybe I'll just do the big tuneup first and see if it helps.

[TimTyler]

I noticed last time I did an oil change that the oil level slowly climbed from halfway up the sight glass to past full after a few weeks of riding. 

My oil level also rises about a half inch after the first few hundred miles following an oil change, but it stops rising at that point. I attributed it to the oil's reaction to heat but I'm no scientist.

I had a similar rattle sound that was more prominent at idle and with a cold engine. Fine tuning the engine completely eliminated it. My exhaust valves were very tight.

[jetpoweredmonkey]

I had a similar rattle sound that was more prominent at idle and with a cold engine. Fine tuning the engine completely eliminated it. My exhaust valves were very tight.

Music to my ears, Tim!  I believe I'll let the output shaft alone.

Love your profile pic, the back of that motobrick looks like Darth Vader's gatling gun.

[jetpoweredmonkey]

Good progress tonight stripping things down...this bike is 100% unmolested.  I love that. 

Sent off the injectors to Mr. Injector to be cleaned and checked, just because she deserves it.

While the valve cover is off I thought I might remove and re-seal the cam chain cover, it seems to have a weep along the bottom, and I can check on the cam chain guides.  Can this be done without disturbing the timing?  It sounds like a dealer-only proposition to reset the timing.  I sure wish they'd put in a timing window somewhere for us home garage hacks.

[Inge K.]

Can this be done without disturbing the timing?  It sounds like a dealer-only proposition to reset the timing.  I sure wish they'd put in a timing window somewhere for us home garage hacks.

From the Haynes manual:

[jetpoweredmonkey]

Just what I needed, thanks Inge.

[jetpoweredmonkey]

Got the final drive, swingarm and transmission off without any fuss tonight.  The K vs. an airhead reminds me of my Vanagon vs. an old Bus.  The air cooled machines are simpler but I am certain that the water pumpers are easier to work on!

EXCEPT...where the heck is the circlip that's holding the drive shaft on?  Is it at the front of the shaft or in the middle of the universal joint?

[Gubro30]

It's on the transmission output shaft I believe, you don't see it but it'S there.

Grab the drive shaft gently with vise grips and a rag and tap it with a hammer - it will pop out easily. Reassembly is the opposite, give it a firm tap and it will click back in.

[K75RT Keith]

By the time you buy the parts to refit the injectors, you may as well send them out for cleaning.  For a few bucks you finish the job and may not need to take them out later for cleaning 

[jetpoweredmonkey]

Thanks again guys. 

As for the injectors, I agree, they are enroute for cleaning, I was going to just re-seal them but they were looking grungy, so I figured it was cheap insurance against another tear-down!

[jetpoweredmonkey]

My brick is doing its best impression of a Star Wars snow speeder.

I think it's come apart about as far as it's going to, and now it's starting to go back together.  Today I removed the calipers and fettled them, and pulled the triple clamps out for re-greasing.  There was a lot of preload on the bearings and the steering was stiff, although the old grease was in good shape, even though it had pretty clearly never been apart before.  Also pulled all the wiring plugs apart and shot the contacts with Deoxit.

The fork sliders were looking faded so I sent them off for a fresh coat of paint at my friend's paint shop.  Those forks are easy to get apart, just remove the bolt at the fork bottom and the sliders come right off, no need to fool around with the caps and spring stack as far as I could tell.  I think you could replace fork seals just by removing the wheel and brakes.

I have my injectors back from Mr. Injector and they look great.  I was going to put the fuel rail in tonight but I have a question.  The injectors came back with new o-rings but I had a pack of o-rings from EME that I wanted to install.  There are two different colors, brown and blue, four of each.  Does anyone know which goes where?  I'm guessing one tolerates heat better than the other...?  Link below:

http://www.euromotoelectrics.com/Fuel-Injector-O-ring-13-64-1-437-474-p/boinj-oring474x8.htm


photo by jetpoweredmonkey, on Flickr

[orforester]

Nice bike, clean shop, can I trade you shops? 

I am working on another spline lube, darn there are alot of pieces to take off. 

[jetpoweredmonkey]

Found the answer - the blue o-rings go on the fuel rail side, brown to the cylinder head.

Next question - valve shims - where do you guys get 'em?

[TimTyler]

Next question - valve shims - where do you guys get 'em?

My local BMW dealer service manager let me trade in my old three for new three.  :2thumbup:

I think there are some Japanese bike shims that'll fit too if that's easier.

[jetpoweredmonkey]

Thanks Tim, I'll try there first.  Someone is selling individual shims on ebay too.

Got a little more work done today.  The rear main seal was leaking, a new one is on the way.  In hindsight I think the leak was due to my rising oil level issue, when I parked the bike, the oil level was at the top (probably above) the sight glass.  When I pulled the clutch assembly off the output shaft, oil poured out of there.  I don't think that seal is supposed to hold oil back at rest, it will migrate through eventually.  Still, no way to know for sure, so a new one will go in once it arrives.  I spent some time cleaning the grunge off the inside of the bellhousing, I'm running out of stuff to do while waiting for parts, why not!  I also made some guide pins to reinstall the transmission, dead easy, hacked the heads off a couple of bolts and slotted them for a screwdriver.

To install the new seal to the correct depth (not flush like the original), I'm going to try cutting a circle spacer out of an old yogurt tub lid.  I should be able to use the old seal as a template and just tape it up to the back of the crankcases to act as a stop.  Looks like it is about the right thickness.

Another task for today was installing a battery cable kit from Euro Motoelectrics.  When I bought the bike, the battery was three years old and I had a big trip coming up, so I replaced it because it seemed to crank pretty slow.  The new battery was not much better.  Looking at the wiring, especially the pitiful ground wire, they looked like they would be hard pressed to run a turn signal, let alone a starter.  The EME kit looks like it would have no trouble powering a welder!  The new cables were a little fiddly to get through the rubber grommet into the electronics box, but otherwise easy to install.  You just run them parallel to the existing cables, and throw away the old grounding cable.  Can't wait to see how she cranks now!

Man, this bike is in good shape.

Got my valve adjusting tools ($28) and clutch pilot tool ($18.50) in the mail from Kenneth Lively a few weeks ago.  They are really well made and a real bargain for the price.  If you need a set, Ken's email is polepenhollow@yahoo.com.

Got my injectors and rail reinstalled too.  The blue o-rings go toward the fuel rail, brown toward the cylinder head.  Mr. Injector cleaned these for me and they came back looking like new.

[mystic red]

I think you could replace fork seals just by removing the wheel and brakes.

That's the way I do it. :2thumbup:

[jetpoweredmonkey]

Got the fork lowers back from the paint shop today.  Looking good!  Also got a big expensive box of mostly tiny little parts in the mail!

[jetpoweredmonkey]

Stayed up way too late and got a lot done tonight.  Installed the new pressure regulator, rebuilt the forks and got the front end together with new seals and gaiters.  I'm glad I hassled with getting the forks painted, they look like a million bucks!

Hit a snag.  I'm getting ready to put the clutch back in, and I see in the Haynes that there is a thrust washer that's supposed to go between the clutch housing and the output shaft.  I can't remember removing this part for the life of me, I have things well organized and it's nowhere to be found.  Is it possible that some bikes don't have it?  The fiche says it is either 1mm or 1.25mm thick.  That is a big gnarly washer, I can't imagine misplacing it.  It doesn't seem to be stuck to the back of the clutch housing or the end of the shaft.

[jetpoweredmonkey]

Today I discovered my missing thrust washer.  When I pulled out the old output shaft seal, chunks of plastic fell out from behind it.  The remains of the washer.  It looks like it somehow self destructed and has been kicking around behind the seal for some time.  Some parts of it must have stayed in between the clutch housing and output shaft, because the nut was still tight.  I was surprised to see it was made of plastic, but this has to be it, you can see it in the photo on the flanged part of the clutch housing where it lives.  It's exactly 1.0mm thick as the fiche indicated it should be.  So, I feel better because it turns out I didn't lose it after all!

Unfortunately it is not complete, there are some small pieces missing, I suppose they must be down in the sump, or maybe they were pulverized by the output shaft bearing, who knows.  The bits that did come out are kind of rounded on their broken edges as if they've been washing around in there for a while.

I was surprised to see this washer is plastic, I will be curious to see if the new one is too, I hope not, because BMW wants $25 for it!  For anyone going in to do a spline lube, I sure think it would be worthwhile to pull the clutch housing off, replace the o-ring under the outer nut/washer and look to see if your thrust washer is still intact.

[frankenduck]

The thrust washer is part 9 here: http://www.ascycles.com/Illustrated_catalog2/MicroList.aspx?id=51752&catID=21&catname=Clutch&bindName=Clutch&bindCat=21_0251

[Inge K.]

The thrust washer is part 9 here:

Trust washer is part # 10.

[frankenduck]

I always thought that was the name for the washer in front of the clutch nut.  Learn something new every day...