I like to avoid rtv because its not very fuel resistant. Permatex,yamabond,hondabond (same thing) non hardening fuel proof sealant is great for small engines however. I use felpro gasket material, I guess they call it imbeded fiber material or something of that sort. Its basically an asbestos gasket replacement, no sealant needed in most cases. Take note of the base gasket (between the cylinder and the engine case) thickness, changes in gasket thickness change port timing and alter compression. This can be good or bad. Too thin of a gasket will increase compression but the piston won't fully uncover the ports so power may be lost. You may also run a risk of the piston hitting the head or spark plug. On the other hand a thick gasket can be used to raise the port timing slightly but it will slightly decrease compression. After seeing the gaskets shipped with some kits I'd recommend making a new set of top end gaskets from decent material. You certainly don't want an air leak robbing you of performance and messing with your jetting.
