So I been tinkering with a husky 61 I picked up a few months back. Ended up putting a jred 630 top end on it with a HS224 carb and non baffled muffler. I wanted to keep it 61cc but also perform well hence the closed port 630 cylinder. Anyway I had a hard time finding a good piston for it but eventually found a NOS 630 piston. As you can see, there were changes made to the windows (and rings) over the years. Two ring piston has the biggest windows, single ring piston (last pic) has slightly smaller windows, and NOS piston has the smallest windows. I figured the new piston may not perform as well as the others because of the smaller windows. Turns out I was wrong. Had to open the high speed an 1/8th turn or so to get it to not rev to the moon. Also had to adjust the low speed a touch. It appears they were able to improve the flow through the smaller windows, or so it would seem. Better velocity into the lower transfers? Still thinking on it.
