Originally Posted by cannonball2
The FM80 crank/rod are the 38mm stroke/long rod of the GT5. The piston should come to the top of the 40mm stroke jug, but wont travel as far down , maybe affecting timing. It would follow logic that the GT5 jug is timed for this crank. But who knows for sure? I don't do porting so Im not well versed on the subject. I posted further back pics of the GT5 engine I have and the ports with the piston at TDC/BDC. Maybe that will help you see what you have.
Not to argue a point here but, the only jug that the piston in a GT5 will come close to the top of is a GT5 jug.
I just shaved 0.030 off of a GT5 jug today to get better squish on the GT5 Im going together with, the jugs for the 40mm stroke engines need about twice that much taken off then to get piston where it will have best compression.
there are a couple ebay vendors that sell GT5 type engines only and all there parts like pistons and jugs are GT5 parts.
when I get on my computer later I will post a couple links here to point to those parts.