Paranemertes:
i was thinking 48 or 72 volts. that means up to 300 amp speed controller, like these:
How much power are you expecting to have? Presumably you're taking some type of battery with you, so you have a limited amount of energy available. 72 Volts at 300 Amps corresponds to 21kW or about 30 bhp in old money. That is a heck of a lot of power to deal with on a light bike, you will be doing burnouts and pulling wheelies. For a couple of minutes, until the batteries go flat.
I think you probably need to produce some realistic estimates of the physical size of battery you can afford to carry, the amount of electrical energy available within that size using affordable battery technology, and then work out how long you need to run for; that will give you your average power output, then you can start figuring out your peak power output and motor type, gearing etc and what you need to control all that.
I would be surprised if the answer was anywhere near 300A.