i got a kawaski teryx, and with all my stuff into it, it goes around 74mph.

but the biggest part is the CDI box, and everyone here is talking about junk ones, ***** all that grizzly and dynatek, get you a VELOCITY CDI box, it will make u probably from that little 39mph to maybe around 50-55mph, mine was a little higher, bcus stock teryx is around 50 alredy, it brought me up to like high 60's, then i got all my other stuff such as my 840 clutch kit, and muzzy exhaust, but i reccomend the Velocity CDI box