right on sounds like you got it going pretty good did you ever look in to new cdi boxes. i dont know if they are using one to limit the revs it can reach i know that yamaha does and i swapted my sons right out plus see if your carb is opening all the way yamaha only lets there 16 millmeter and 20 milimeter for the 50 and the 80 cc mahcines open have way so i jeted it and cut the slide valve so it would open all the way and with a pipe and the new cdi box it will keep up with my 660 in mid second gear he s on a 50 cc raptor plus a widing kit and slightly taller fronts and wider rear tires it s running very fast and pulls up all kinds of hills and since the rigs are shaft driven all of the above mentioned is what i found to work p.s. look in to new cdi boxes the one i used for my sons quad cost 123.00 plug and go. happy safe and sane riding