Jackshaft questions

Ok i have a modded preadator on a mtd trail flite...which is somewhat like a rupp. Mini bike has a jackshaft setup and when i got bike i had to restore it so didnt know the exact gear ratio. So...the ratio i have now is: 12th clutch, 14th jackshaft to 10th, and 60th rear sprocket. When im cruising and give it full throttle it seems like engine is reving too high and im nit going that fast...what is a good hear ratio for medium torque and higher top speed?