psiton and spacer plate question

[zedicus00]

what thickness of spacer plate do i need to use to run a yz piston in a shortrod motor? how well does this setup work? actually any info on yz piston in 250r motor is welcome.

also what would need dun to be able to run a cr250 piston on a 250r shortrod motor?

[wilkin250r]

I don't know the exact specs on all those pistons, but there are MANY considerations.

You want to make sure that during the compression stroke (which is also your crankcase intake stroke) that your piston skirt is long enough so that it doesn't uncover the exhaust port.

You need to make sure the rod is compatable with the piston pin, and that your piston skirt clears the crank at BDC.

You'll need to map the ports and figure out your timing.

There is a LOT more going on inside your engine than just bore size and head clearance. In a 2-stroke, you're also adding in the factors of your crankcase and port timing, a worry that 4-strokes are not plagued with.

I don't have all the answers, but I can tell you that it's much more complex than a simple spacer-plate thickness issue.

[baker250r]

why not run 86 style piston with a spacer plate, if ur not runnin a 86 motor already

[racerx573]

Call Sparks about using the YZ piston.

[beerock]

you have to relocate the ring pin to be completely safe, its near the exhaust port and gets hung up sometimes if left stock i believe

[outlaw#9]

i had a yz piston on a hyperdyne cylender i had years ago ...i use the same spacer as the 86 piston with a long rod crank ..the ring gap was moved to the other side of the piston tho .. im not shure why duncan used that over a 86 piston :confused: