use high-temp RTV on the intake and exhaust gaskets. Also where the carb connects to the intake manifold.
As Bikeguy said, clean air filter regularly and make sure your air/fuel ratio is correct. And check all nuts/bolts regularly.
You can get a new gasket for the gas cap if it's leaking badly. A little bit here and there is normal, as the cap has to vent for it to work.