As appears to be the custom on this forum, I'll start a new topic for the bike here and answer some of the responses from my new member post. I'm not really looking for answers but it's theraputic to have a bit of a moan. Feel free to chime in.

To recap, it's a K100RS 16V in black with 85k miles on it. Manufactured May'91, first registered Aug'92. Not been used for the past 3 1/2 years. Aside from some cosmetic tattyness and non-functioning ABS, it has the following faults keeping it off the road:

• Clutch gone. Rideable, just, but won't take much throttle or revs.
  
• Radiator leaking - badly.
  
• Two out of three discs below minimum thickness.
  

In answer to 92KK 84WW Olaf:

• I checked on Tosi's site. The ABS control unit doesn't work and, because of corrosion on the board, might well be beyond saving.
  
• The radiator was described by my local radiator repair centre as a 'sieve'. I spotted one large hole, they found 6 more. They can't get a new core for it so, hello James Sherlock.
  
• I read the description for the front brake caliper repair kit on Motorworks' site; I'll try to get away without splitting them
  
• The exhaust studs are rusted up so I'll have to pull the studs out of the head - carefully.
  
• At the moment, my money is on the rattle being the two allen keys sitting between the battery box and gearbox shell. But I'll run it up with the alternator off before splashing out on new rubbers.
  
• I hadn't thought to do the crankshaft seal if the clutch is dry. But maybe that's a good call while it's apart.
  
• It has the 3.50x17 three-spoke front wheel, I haven't seen many of those up for sale.
  

In answer to JGT:

I think I paid too much for it, in fact, I think I've been had. A radiator is going to be around £100, clutch plate £84, although if I'm unlucky and it needs pressure plate and cover plate, that's another £200, At this point, since I have no particular affection for the bike, I start to ask whether it's worth doing. I think your suggestion of £1000 for a runner with 12 months MOT* is a little low but I agree, they don't fetch much. Then again, that means lot's of cheap-ish second-hand parts around. But if I can't see a way to get it on the road for £1200 this one might well be for the chop. Anyone interested in a K750xxx UK registration?

*MOT is UK annual safety check.

Thing is that if you do that lot you have a good K.

On your list a few things can be had sometimes quite cheap. 

1 Clutch. Could be clutch splines need lube, if its sticking on the splines it will act like its gone. Look at the little hole under the bell housing and see if its dry. It smells of neglect so odds are these are not done and you might be lucky. The gurus take out the bell housing bolts and use two bolts to keep it all aligned and just slide it back an inch or so to get a look in. Ideal is get a K mate to help you. Might just be worth taking a look. Having said that my K100RT got a clutch at 78k miles [I had it since 36k miles] but also rear main seal and all the other bits and seals. Also check the picot arm bearings, they too could be seized not allowing the clutch to drop fully.
2 Rads are never really worth fixing, go for a used one and its an easy enough swap. While you are at it check the fan works. They usually die, seize or whatever. There are cheap options for motor replacement etc but don't wast time buying a used one, it will die too.
3 The front calipers if split are difficult to reseal. You don't need to split them.
4 Look at your headers and see if you have a loose exhaust flange. If the studs are good leave them and use lots of WD 40 and if you need, a splitter. Sometimes the nut comes off, sometimes the nut doesn't come off and the stud comes out. Honda studs fit perfectly too, I just discovered.......Being a 16v also check where the headers meet the silencer, they split there. For cheapness you can fit a 2v exhaust, cheap and plenty out there.
5 Buyers will look for these things done, document it well because if you are selling on proof of rear seal and clutch is one thing that buyers fear.
6 I think your front wheel is K1100RS? If it is there are lots of them out there.

Having owned two of these wonderful beasts so far, here are a few thoughts.

First, clutch slipping can be caused by badly a adjusted clutch mechanism and cable.  Go back and carefully check the adjustment of the cable and the bolt that pushes on the clutch pushrod.  Olaf's recommendation to check the clutch splines is also important.

Second, how worn are the brake rotors?  If close to spec and not warped, new ORGANIC pads will stop the bike for a while until you are able to source a usable set of used rotors.  I would avoid really aggressive riding until they are replaced.

Third, where does the radiator leak?  As mentioned, there are good used radiators to be had.  I have gotten a lot of good used parts off of ebay.  You might want to replace the OEM fan with a Spal fan.  It's very possible that the blades slid forward on the shaft and ran against the radiator core.  This is not uncommon.  A new fan along with a good used radiator should get things working properly in the cooling department.

Regarding cooling, a used radiator will benefit from a good cleaning inside and out.  An hour or two soak in distilled white vinegar will clear out any mineral buildup inside the radiator and soften up any insects in the fins so they can be flushed(from back side to front).

The ABS system can be removed to lighten the bike by about 10-12 kg.  If you are adventurous, you can even remove the main harness and delete the wiring along with a rewrap of what's left to make a really clean looking harness.

What is the problem with the 3.50x17 front wheel?

A little good news regarding the radiator.  The same radiator was used in later model 2V K100's as well as K1100's.  For some reason, K1100 parts don't sell for as much as K100 parts even when they are the same so you might be able to find a better deal by looking for K1100.

Point-Seven-five wrote:A little good news regarding the radiator.  The same radiator was used in later model 2V K100's as well as K1100's.  For some reason, K1100 parts don't sell for as much as K100 parts even when they are the same so you might be able to find a better deal by looking for K1100.

And K11 rads are newer too.

I have to disagree with Olaf over splitting the front brakes. No; Brembo don't supply the little o-ring that seals them. Why not, I have no idea because it's the same o-ring as they do supply in the P08 caliper overhaul kit. However, yon little devil has a BS part number and I just happen to have fifty of them sitting in my spares drawer. PM me.

Good luck with your project or resale, stanthomas, whichever happens.

My thanks to everyone here.
Firstly, to address some of the questions:

• The radiator has passed on, it is no more, it has ceased to be, it's expired and gone to meet its maker...
  
• The fan, however, is working fine.
  
• I checked the clutch adjustment as per the Clymer manual; it was fine.
  
• I don't know whether there's anything wrong with the front wheel; it's been repainted and has some marks on it that could be signs of being straightened. It will need to be examined before running on the front of a 130mph, 500lb bike.
  
• The discs measure: front left 4.11; front right 3.51; rear 3.27. My understanding is that the minimum thickness is 3.55mm.
  

It's very clearly been neglected. Perhaps the clutch started slipping with last but one owner who then chucked in a corner before finally selling it on. The rusty water that came out seemed to have very little of anything resembling anti-freeze so chances are the radiator spent the last 3 1/2 years quietly rotting. What I can see down the coolant passages in the engine block doesn't look too bad though.

It hadn't occurred to me to look at K1100 parts; thanks for that tip.

Now Olaf made the perfectly valid point that if I fix everything on the list I'll have a very good K. But there's the problem, and the reason for this discourse - I don't know whether I want a K. I've never ridden a K and, without wanting to upset anyone here, it might be just another heavy, sanitised, water-cooled, 4-cylinder. I hope it's not and the plan was to get a couple of hundred miles out of this one before needing to spend any money. Then I'd know. whether I like it. If I do there's no problem doing whatever it takes to make it good 'cos I'll be keeping it.

To go off at a tangent for a moment, I have an '81 R100RS. In 1981 I blagged an extended test ride of the exact same model during the Isle of Man TT. I was impressed with the way it rode the bumps and what you might call 'effortless speed'. But it was a bit sedate, a bit too upright, an old man's bike. So I bought another Ducati. Now I am that old man and the R100RS hits the sweet spot between a raw motorcycle and a practical ride; you know, electric start, oil tight. all that stuff but with clattery valve gear, carburettors, petrol taps you have to turn on and off, brakes that are only just good enough. What Pirsig might call soul. But it needs some tlc, so what better than its offspring to run around on.

Anyway, thank you all for the opportunity to meditate on the subject. I've decided to try to put it back on the road for the minimum I can get away with. Which at the moment is a radiator and, probably, a clutch plate. Fingers crossed my friendly MOT tester won't bother measuring the rear disc.

Look on ebay for organic carbon kevlar brake pads.  They stop well and are pretty easy on the rotors.  Downside is that they seem to be a bit dirty.  I use them on all my bricks and am getting upwards of 20,000 miles from them.

I get them for about $20US for six pads for all three calipers.

https://www.ebay.com/itm/Front-Rear-Organic-Brake-Pads-1991-1992-BMW-K100RS-FL-Set-Full-Kit-16-er/163962621090?fits=Model%3AK100RS%7CMake%3ABMW&hash=item262cef0ca2:g:E5UAAOSwJcNd3Zr4

Regarding your needs in a bike, I'm an old man(71) and enjoy the performance from my 16V K100RS.  It's handling feels light, accelerates with urgency and feels comfortable at 90+mph.  It's also reasonably easy to work on.

Min spec for the front rotors is 4.5 mm
Min spec for rear rotor is 4.57 mm (has 0.18" printed on it)

(From BMW shop manual which I have hosted here: http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/shopmanuals/BMW_K1_K100RS4V_Repair_Manual.pdf )

To recap, it's a K100RS 16V, '91 with 85,000 miles.

Radiator replaced with a K1100 one from James Sherlock. Pretty good nick. Decent thermostat too. Flushed and refilled. Engine fires up, no leaks. One down.

Now. Shaft off, gearbox out, clutch pulled. As you can see in the pictures, the clutch and housing is soaked. Seems to be coming past the o-ring on output shaft (and has been for some time). O-ring has hardened up and is clearly past its best. Main output shaft seal looks to be dry but I'll replace it together with the o-ring and the gearbox input shaft seal while it's apart.

One oily clutch:


So wet you can see reflections in the oil:


Looks dry behind clutch:



My questions, and there are a few. Sorry to go on but I'd appreciate some expert knowledge.

1) The clutch/output shaft nut wasn't tight. Saw the torque setting and was ready with a pipe for the breaker bar but the nut almost fell off. Is it common for this nut to be loose?

2) When I had the engine running it sounded like a bag of nails at tick-over (1000rpm). Noise coming from the back of the engine / clutch area. Pretty much went away at 2000rpm and above. Hot or cold. Alternator was off. Yes, it's running roughly and needs a good tune-up but is it normal for these bikes to clatter at tick-over? Is the finger-tight clutch retaining nut a likely cause? Is there anything I should be checking while the back of the engine is exposed?

3) The output shaft seal has some green gunge around its outside. Is that the way BMW assemble them? Should I give the new one a smear of Hylomar?

4) Clutch friction plate thickness is 5.0 mm at inner edge, 4.8mm at outer edge. Presumably this taper is reflected in the inner and outer pressure plates too. Is 0.2mm of taper going to be an issue when only the friction plate is renewed?

5) How important is keeping clutch components 'as assembled'? The plates have clearly been drilled for balance. And there are no paint marks in sight. Is assembly balance still a concern on these bikes?

6) When I pulled the final drive off the swinging arm, the rear UJ stayed in the shaft. The splines at final drive (back) end of the UJ were well greased, the splines at the shaft (front) end were quite dry. All splines in good shape however. Is the rear UJ free to slide at both ends, and therefore should be lubed at both ends, or is is retained in the shaft somehow?

[Edit] to answer my own question, on 16Vs the UJ is retained in the final drive by a snap ring similar to to one at the gearbox end. So it will come away from the drive shaft when the final drive is removed.
There is less fore-and-aft movement on the spline at the final drive end compared to that at the gearbox end but should be greased (MS2 paste) anyway.
Forward snap-ring is part:26 11 1 451 977, rearward is part:26 11 2 310 656.

7) Finally, the pivot pin for the clutch operating lever looks far longer than necessary. Is this the right part?

1.  No

2.  My 16V K100RS's idle rather nicely.  The loose clutch could definitely be a source of noise.

3.  I installed those seals on my bikes with a thin film of petroleum jelly just to make them slide on a bit easier.

4.  I have no idea if that taper will be a problem.  I guess it can affect the amount of force exerted on the assembly when engaged.  You'll just have to see if it slips while it beds in. If you stack the two plates together is there a gap at one of the edges?

5.  Go back and look very closely at the clutch parts and find the marks.  On some assemblies I have taken apart they were almost invisible.  They need to be spaced 120 degrees apart.

6.  When I do the drive shaft I lube every spline. 

7.  I can't say if it's right or not.  It's been a long time since I looked at mine.

5: I was in the same position once. I used a static wheel balancer to to try and identify the 'heavy' points on the individual clutch components, and so offset them by 120' on assembly. It didn't work. I think the manufactured clutches are thrown together as a set, and then drilled as one to balance. There's 9 permutations, I got fed up of trying to solve it and I just put it back together anyhow. The bike didn't fly apart and I'm either immune to vibration (likely by now) or things weren't too bad.

6: I'm fairly sure the rear part of the driveshaft is secured on the bevel box input shaft with a snap ring. The only sliding movement takes place on the long splines within the driveshaft itself. As advised, all splines should be lubed though.

7: The extra bit of shaft is for a mechanism to automatically retract the sidestand when the clutch is pulled. Not BMW's finest hour, lots of owners remove them. Also, if someone's replaced the shaft with a new one, then maybe that's what was supplied. Not a problem until you try to remove the shaft and find that the corrosion on the spare bit prevent withdrawal. (There's some nasty rumours circulating that I've used an M8 bolt instead of the that shaft on several occasions..... )

Thanks for the advice. I'll order the parts and see what it sounds like when it's back together.

Ordinarlly I'd be looking at a nice ride thru the Peak District to Motorworks; seems I have defer to ParcelForce this time

I found the clutch balance paint marks. The marks on the pressure and cover plates were easy enough to spot after a good clean but that tiny, tiny fleck of yellow on the clutch housing would have been lost forever were it not for inferring it must be somewhere in the "other" third.

I bought used clutch from a 100k mile K1100 in better condition than mine. The machining marks are still evident so I'd guess it had a complete clutch some 20k miles ago. With a new friction plate it should be good to go.

Clutch operating arm pivot pin is firmly seized; even welding a bar on and trying to put some rotatation into it just ended up shearing the pin. Trying to drive it out with a hammer will likely break the gearbox lugs so, taking the advice on this forum, a used arm is winging it's way to me and I'll cut the old arm off with a grinder.

As previously mentioned, the engine sounded like a bag of nails at tick-over. Just like the first video in this  this forum topic (My clutch 02)

To try to discover why,  I refitted the clutch housing in the back of the engine and torqued it up (the nut was not tight when I took it apart). Left the plates off and bolted the gearbox back on to mount the starter and exhaust hanger. And the clatter has gone. So either the clutch was loose on the output shaft or some part of the old clutch was rattling. I'll do the seals, fit the replacement clutch with new friction plate and try it again but at least I know the cause.

Now we come to the question de jour:
There is still a noise coming from the back of the engine in the region of the intermediate housing. Not a rattle this time, more like a bicycle freewheel but a deeper note. Might be from the vicinity of the alternator drive but loading up the alternator coupling with a block of wood doesn't quieten it. Nowhere near as loud as the original clatter and I might not have bothered about it if the bike weren't already in bits. The rest of the engine: cam box, bottom end, oil/water pump are quiet and sound good. But there's definitely something going on in that intermediate housing and I'm inclined to pull it off and take a look. Before I do, is it normal for a freewheely type noise to eminate from the intermediate housing area, louder than the rest of the engine? Are the starter motor sprag clutches noisy (running, not starting)? Any bearings in there subject to early failure?  Anything I should look for on a 16v with 85k miles?

Thanks.

Fit a grease nipple to the clutch arm is a wise move, as well as waterproofing the GPI switch while your there.
Regards Martin.

I was going to put plain bushes in the clutch arm with a stainless pivot. I have done this systematically on my airhead. Needle bearings are an unnecessary complication in this application and, as we see, prone to corroding and seizing. If the plain bushing wears after 20k miles, which is quite a few years these days, the pin will still pull out and it's cheap and easy to replace.

Any thoughts on the noise in the intermediate housing?

Try running with the alternator removed, see if it makes a difference. See if you can pin down the source of the noise with an automotive stethoscope, they're not dear or alternatively a long screwdriver.
Regards Martin.

@MartinW Alternator's off. Noise is definitely inside the intermediate (aka bell) housing.

One thing I haven't tried is torquing the alternator coupling centre bolt, that was the solution to one discussion of a similar noise on this forum.

I would add that this noise is engine speed, from tick-over and up and is there hot and cold.