Thursday, December 8, 2011

BMW R100S Clutch and top end assembly

I retreived the newly rebuilt cylinder heads in San Diego yesterday so decided to assemble the engine top end this morning. When I originally pulled the R100S engine apart, years ago, it had cylinder base metal gaskets installed. Unfortunately I tossed them thinking that new ones would be used. I then found out that the base gaskets were not used on these engines. The later engines had an "o-ring" groove on the cylinders for sealing. This engine had no o-ring grooves so sealant was necessary to seal the cylinder to the engine.
I want to reduce the engine compression a bit so I purchased a pair of earlier base gaskets and then trimmed down the interior diameter to fit over the engine cyliders. All I have is a small Dremel type tool so I spent probably an hour on each gasket, trimming down the interior diameter to fit over the cylinder base.
Hopefully the base gasket will not reduce the compression too much. I saw signs of detonation on one piston so reducing the compression should hopefully make the engine run a little cooler and get rid of any "pinging".

The base gasket in place prior to cylinder head installation.

I cleaned up the pistons / ring grooves well before installing them in the cylinders. There are also a couple of o-rings on two of the cylinder studs. I made sure they were properly in place before installing the heads. I previously had pinched one of the o-rings causing a minor cylinder base leak.

Brand new Black Diamond Valves, Valve Seats and o-ring valve guides.

I actually spent more time modifying the base gaskets than it took me to assemble the engine top end.

I then turned my attention to the clutch assembly. I ordered a set of special bolts needed to back off the pressure plate assembly. Once the clutch came out I was in awe that it even worked. Two big chuncks were missing from each side. The pressure ring / pressure plate are grooved and worn down. This unfortunate developement will require replacing everything in the clutch the tune of $500.00 or so.....

Suprisingly the fly wheel has been lightened and balanced.

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Gila Mtns.

Gila Mtns.