You didn't say but we're assuming you have a Chinese 2 stroke engine.
There is a lot of discussion here >
http://www.google.com/cse?cx=partne...sc.tab=0&gsc.q=head gasket leaking&gsc.page=1 about head gaskets and how to keep them from leaking.
Basically we recommend a few things to do.
1. Get rid of the chrome acorn nuts and use hex nuts.
2. Lap the cylinder head to achieve a good gasket sealing surface.
3. Use a torque wrench, tighten the head fasteners to 120 to 140 inch pounds using a cross pattern (corner to corner)
4. Replace the head gasket if you see any sign of damage or area where it has 'blown out'.
You'll also want to make sure the studs are threaded into the engine case correctly. If the acorn nuts have damaged the threads, and this is common, run a die over them to restore them. (Keep any metal chips from falling into the cylinder)
Tom