84 R100 Top End [Archive]

gfdunn

02-08-2009, 04:14 PM

I am going through my top end with new seals & gaskets and since it's apart wanted to go back with new rings of course after honing. The pistions and cylinders are in good shape. There is a local shop that carries airhead parts and they told me I could not buy rings for the pistons and that I would have to buy the complete piston heads with new rings on them. This seems like BS so I thought I would ask you all. Surely someone sells ring kits.

Thanks much, Catfish

20774

02-08-2009, 04:31 PM

You have Nikasil cylinders. They have special rings. Also, be careful on the honing. Generally, you don't hone these type of cylinders. You should still see the original cross hatching.

Don't know about having to buy pistons and rings together, but you're options are a little limited with the Nikasil stuff.

RandyB

02-08-2009, 05:34 PM

They're called cast iron.

Try Fed Mogul part # E-495x5594

That'll get you enough for 4 pistons.

gfdunn

02-08-2009, 09:44 PM

Thanks Kurt. Actually eqfthe cylinders are still great with the original crossing. I still should still be able to get the rings though right?

20774

02-09-2009, 06:30 AM

I still should still be able to get the rings though right?

Don't see why not. Hucky's BMW has them listed http://www.bmwhucky.com/. Be sure and measure the ring gap on the existing rings and also the bore to confirm what size you need.

sumran

02-09-2009, 06:52 AM

What is the mileage on the top end? Are the pistons already out of the cylinders? Is it burning oil? That set should go many miles without needing a change. Your money, your motorcycle (YMYM?) but they may not need to be changed.

lkchris

02-09-2009, 09:22 AM

Don't see why not. Hucky's BMW has them listed http://www.bmwhucky.com/. Be sure and measure the ring gap on the existing rings and also the bore to confirm what size you need.

Confirm the "bore size you need" by observing marking on cylinder base--either A, B, or C.

Curious whether compression test has been performed.

Most likely need for "repair" on this engine is exhaust valves and valve seats. The cylinders are basically indestructable.

If you really insist on spending money on the cylinders/pistons, best bet is to buy a new matched set, i.e. cylinders with pistons. There is no repair possible/feasible to nikasil cylinders and it's VERY seldom any is required.

gfdunn

02-09-2009, 03:21 PM

Thanks guy's. I should have my measurements tomorrow and will post the other answers then.
Catfish