one thing is they are light compared to anything else, if you want a guinea pig to try porting on they aren't bad for that. I have a bunch of them but haven't gotten the ones I have converted in flying planes yet though (will this summer). There's several sizes of the things, 18, 21, 24 and 25cc, the 18cc is the lightest as I have had one stripped down for gas/glow with prop and it was right at 2lb... I degreed one once and I think it was at like 115 degrees exhaust duration where it should be near 150 degrees, but I think that was the 24cc which is labeled as a low emission engine...