Hi,

I have a valve chain which really needs replacing on my K75. I have a spare K100 motor on the floor. I'm fairly sure that I do not even want the know the price of completely changing the valve timing chain and associated gears, so I need to know whether the valve gear is identical and I can just swap between the two motors.

To save me stripping down the spare motor and stripping my road bike to check dimensions, can some knowledgeable person tell me if this is possible. Maybe if timing marks are a little different, or any gotchas.

many thanks.

If your spare engine is a 2V K100, then according to the parts fiche at MaxBMW, the part numbers for sprockets, chain and tensioner are identical. Have a look here at the full list then compare with a K100 of your choice using the site's Change Model function.

many thanks, that's just what I was looking for.  Time to get the spanners out. 

Here's a comparison of the part numbers from RealOEM:

Great help , thanks.

The only difference I have come across is the hydraulic tensioners are different. They are interchangeable and either will do the job well however IMO the K75 tensioner is a better design.

RicK G wrote:The only difference I have come across is the hydraulic tensioners are different. They are interchangeable and either will do the job well however IMO the K75 tensioner is a better design.

What's hydraulic about the cam chain tensioner? They seem pretty mechanical to me.

It uses oil pressure to hold it tight while running and the ratchet is only there to prevent the piston receding all the way so the chain is not very loose at start up.

Thanks Rick, I'd noticed that the tensioner had a different part no. , your evaluation of the differences is very useful.

realoem shows $100 for the chain and another $200 for the three gear wheels, I knew I didn't want to look !

Are the sprockets showing any signs of wear? I have never seen any with any visible wear.

Well, I'm on false trail here. I was sure that the cam chain was slapping around yet it seems fine. There is some wear on the back of the chain sprockets but as far as I can tell by squinting at it, there is no obvious asymmetry in the teeth. I changed the chain a couple of years back without changing the sprockets and was half expecting worn sprockets would have prematurely stretched the chain. Seems OK though.

My main problem is that it is running like a pig. That's not the valve timing but I thought it may be a contribution to poor tickover and was something which needed checking. If it's OK, I'm happy with that.

I ran it for a couple of seconds with the rocker cover off to check that the hydraulic tensioner was OK and did I not see any slackness in the chain.

I was surprised that just a couple of seconds running dropped quite a bit of engine oil, which ran out of the timing casing. Do you know where is that flowing from? Is that normal?

The oil comes from the camshaft bearing caps closest to the sprockets and the tensioner by the bucket so the chain is fairly much running in a bath of the stuff.