Cometic or oem, clean mating surfaces with red scotch rite pad then ascetone with white terry cloth till all oil residue is gone. Spray head gasket with copper spray and install . Torque as stated
Imo you should have the clearanced checked by a good machine or honing shop. Once he checks cylinder for trueness of bore and piston to cylinder clearance you can make your choice . If you don't have access to anything start with a fresh bore n new Pistons . It pays to get your crank trued n welded also
Start the bike with rad cap off, if it sparays out you got a compromised head gasket or oring . More than likely it's an air leak of some sort. If someone has a pressure test kit it couldn't hurt
I build quite a few wheelie bikes and even have a little port design for wheelies . If your looking to stay pump fuel your gonna need like 24cc domes . I like the dmc pipes or pro circuits . If your not worried about hp output the stock exhaust is great for killing the streets at night . Stealth is the name of the game
I've see an increasing number of shit heard gaskets. How was you cleaning process before you installed new gasket and did you use any kind of copper spray or sealant
Coming from a different point of view I can always tell a bike that's had 40-1&50-1 ratios run through them . IMO get your power somewhere else and give em oil
Soak it, heat it , back it out, if all else fails drill it very carefully in steps. There's also a place in Merrick Colvin auto that will remove for like $10