what do ya need more power for????
hell my lifan has 15hp and i'm not sure if i've used all of that yet
hell i'm not sure if i'm getting all 15 out of it anyway i'm only running a 24mm carby
but if ya must brian at east 50 has got takagawa heads for bout a grand and you will start pushing 20 from that well it will allow up to 12000rpm which will help