I am about to start reassembly of my clutch and Clymer says I should start with the thrust washer on the output shaft. I’m 99% certain I didn’t remove one. Real OEM (item 10 on the fiche) calls this a ‘stop washer’ but it is spec’d in 1 of 2 thicknesses 1 or 1.2.5 mm). Neither Motobins nor Motorworks seem to stock it and there are discussions on here about whether this is a ‘real thing’. Do I need one, and if so how do I find out what size? Bit of a mystery. Apologies cant get rid of the bold.

Cheers, Stu

This is one of the part numbers, 11211460873


PS I have a small (3 or 4mm) amount of forward to back play on the output shaft. Is this normal?

I just did my K1100LT Clutch and it had one.

The part is available from tills.de

Thanks RF. 1 or 1.25mm?

Now that I've checked the diameter I'm absolutely sure I didn't take one out. 

Anyone know what's going on with this esp. As it seems to be there or not depending on the year, the thickness seems a bit arbitrary, and the k75 doesn't have one att all even though that part of the clutch looks the same across models?

G'day Stu, when the main seal and "O" ring was replaced on my 1986 K100RT, the thrust washer was broken.. I got a local parts supplier to get one and it was 1mm. I think the thickness of the washer was stated in the Real OEM website.
Cheers
Tom

Thanks Tom,
I’ll take a punt on the 1mm then. Real OEM shows the same part (diff number) in 1mm and 1.25mm config. There seems to be some very un-BMW inconsistencies in this application, but first I need to get back on the road (cabin fever), then I’ll do some more research.
Cheers, Stu

I recon you've got one alright, it probably stuck to the clutch housing when you removed it, and has fallen off along the way.

If you're working on a concrete floor, you have a good chance of finding it back. Backtrack where you took it.

Have a close look at the housing, it might still be stuck on. From memory, there is a lot of slop in the shaft.

This washer has been discussed before, back in 2013:


https://www.k100-forum.com/t6518-flywheel-clutch-housing

Mike

G'day again Stu, I meant to add to my last post that I measured the broken washer with a micrometer and it came in a whisker under 1mm. So the replacement washer was going to be 1mm thick.
Cheers
Tom

If you are really concerned about the washer thickness using  Plastigage would give you a accurate measurement of the thickness required.
Regards Martin.

daveyson wrote:Have a close look at the housing, it might still be stuck on. From memory, there is a lot of slop in the shaft.

Like anyone could be that dumb.



DOH!

Thanks everyone. 
New 1mm ordered, shame hidden away, moving on with my life 

There's no shame in dumb stuff, it's great for a laugh. I recommend further reading on it,  a UK book I had a couple of decades ago called "the book of heroic failures" which celebrates failure. It was great for a laugh.  I laughed until I stopped.

Actually I thought,  wouldn't it be funny if you looked on the floor for two hours only to find it still on the housing, which gave me the unfortunate idea to edit the post.

daveyson wrote:There's no shame in dumb stuff, it's great for a laugh.

In which case I won’t be embarrassed to mention that I ordered the new one from leebmann24.de, and they sent me a lovely email in English to check that I really did intend to collect in person from Passau, Germany. 

So you recon those two examples are dumb, do ya? 

Try to get your hands on that book, you'll laugh hard. 

I removed a water trap from a sink once.  As I was holding it, I thought hmm,  I can't put this down without the water spilling out,  so I poured it down the sink! 

Beat that!

daveyson wrote:Beat that!

Can’t 

The thrust washer eliminates sliding steel to steel contact when the rubber dampers come under compression, and when the pressure is relieved, even though It's only a small amount.

If the measured clearance doesn't allow enough compression using a 1mm thrust washer after the clutch nut is torqued, a 1.25mm washer could be used. Because of the number of components affected when the clutch nut is torqued, having an option for washer thickness allows for fine tuning of the pressures.

The K75 is a different animal, with balance weights  instead of an absorber, so doesn't require the fibre thrust washer.

If a thrust washer is used that is too thick,  the absorber assembly might not be able to compress, because of the increased friction. If a thrust washer is used that is too thin, it may not be able to eliminate end float of the output shaft, because of the reduced friction.  Since my '86 model was different to my workshop manuals,  I took notes,  and the thrust washer clearance was 0.66mm. and had a 1mm thrust washer.