At my own risk - if you're looking at a 61 size engine, don't overlook the Thunder Tiger GP 61. This is a real bargain powerhouse. I have one on the front of a 7 lbs plane, and with a 13x4 prop, it will drag that plane all over the sky all day long. It starts reliably, idles beautifully, and transition is as smooth as you could ask for. The displacement is actually .65.

Brad