RE: Tecumseh TC200 / TC300
Many people think a long stroke provides more torque, but I have read numerous times that the increased pressure from a large bore piston would equal out the leverage advantage of a longer stroke crank, all else being equal. Effectively, they both should make about the same torque. A shorter stroke engine is better suited to high rpms because it reduces piston speed and friction. A larger bore allows for larger valves, less shrouding of the valves and better breathing for a four stroke engine, and for a two stroke engine a larger bore provides more available porting area. All this means more power potential on a larger bore engine, as well as being lighter.
Normally, full size aircraft engines are of a big bore and short stroke design, as this makes not only the most compact engine, but also the lightest engine. Most modern full size aircraft engines are of the short stroke/large bore design, and they only turn around 2,700 rpms or so. That kind of "takes the wind" out of the "long stroke makes more torque" argument...
AV8TOR