Well, on the Homeys, I think the bridge in the exhaust port is a lot easier to verify....

If you want to know the diameter of the piston, just stick a wooden dowel with a rounded end into the exhaust port, carefully trying to hit the middle of the cylinder on the opposite side. Then rotate the engine until the piston puts a crimp mark in the dowel by pushing it up against the top of the exhaust port. Then measure from the end of the dowel to the crimp mark.

I measure the stroke with a calipers stuck down through the spark plug hole.

(Bore x bore) x stroke x .7854 = cubic inches, assuming you measured in inches. Divide by .061 to get cc.

You can practice this method on an engine with a known capacity. When I do it, I usually get within one cc of the actual engine size.

AV8TOR