Originally posted by mikenlapaz
....they also have a compression release to allow the engine to spin faster .....
Got any pics of this C release? I'm new to this but it is the first I've heard of CRs.
stick a caliper in the plug hole, measure the stroke(s), pull the heads and measure the bore.
WAG pi radius square x stoke = displacement.
Your WAG is correct. That is the way to calculate displacement.
As far as the compression release, it is a really simple mechanism on the side of the head that is operated when the start button is pushed. Small diameter rod with 1/4" head on it and a spring to keep it closed. I'll try to get some close ups of it and post them.
I thought it was interesting.
JimRoss