piston help?

[chamberlain31c]

i've got a long rod motor with spacer plate, what piston do i need 86 or 87-89? and also i have a 21 cc pro design head is this ok for pump gas? or can i go to a 20 or 19 cc dome and still run pump gas, what are my limits? thanks

[chamberlain31c]

also i have what appears to be a cr head gasket(just one gasket no layers) what year gasket do i need or is there a better way to go?

[jon370r]

If the spacer is .190 thick then yes with a long rod you need a 85-86 style piston. There is also the remote possibility that you may have a stroker crank or the oddball YZ piston set up. If you don't know the history behind the engine its hard to tell until it comes apart to find out. The thin shim type head gasket can also be from the outer layers of the 88-89 3pc gasket that you can take apart and use just the outer parts to build more compression and tighten the piston squish area. That way you can get 2 thin head gaskets for the price of one.

[Honda 250r 001]

spacer plate = 86 piston. get atc gasket kit. i believe that head gasket is thinner.

[wes350x]

http://www.exriders.com/vbb/showthread.php?s=&threadid=379868&highlight=what+setup

This may or may not help. this is my setup. I learned its a yz setup with cr gaskets. See the measurements on the spacer plate also.