yer depends on all sorts of things the banshee is the fastest quad out of the factory tho
and the best for tuning as 2 stroke engines are so tunable and 4 stroke engines are limited
I love the 2 stroke engine, and have pushed them further than most, 31hp from 79cc's.
That said, 4 strokes are MUCH more tunable for the average user, have greater reliability and then theres forced induction...
what size rear sprocket have you got on it? ie.. how many teeth