Bump....I have a 65cc cast iron Metra for a Derbi Pyramid reed engine, and the 47mm airsal for my flatreed variant.
The 65 Metra has a 3rd transfer, but neither the piston or cylinder skirt are windowed.
How would I figure out how to make a window in the cylinder skirt in the proper place?
And for the 47 airsal, the cylinder skirt has windows, but not the piston. Figuring out the location of the piston windows is simple, just match em up at BDC. BUT, I see some people here cut away the whole piston skirt, without leaving a bridge at the bottom. Is that safe? I'd be worried about those prongs breaking off the piston.