What's the best way to fix an air leak between the cylinder and crankcase on a 300cc 2 stroke?  I rebuilt the top end a few years ago and now that joint is leaking and causing idle and running problems.  I could just replace the gasket but I'm afraid it will start leaking again.  Would a gasket compound (like form-a-gasket) be good to use?  I was thinking of putting the piston at TDC and lifting the cylinder up as far as I could, without totaly removing it, and applying the gasket compound.  What do you think?  

Use a high temp gasket sealer, and use a 16th inch bead evenly all the way around, and it just might work. Keep in mind that if there are any oil passages to not clogg them, and you might pull it off.Good luck.