I have a x1 pocket bike.wit a sprocket wit 64 teeth. i want to to get better horsepower and more mph.wutdoinee

You need to learn how to spell I can not make that out.

Your gearing has absolutely nothing to do with HP. If you put a bigger front on, it will give you more top end but less acceleration. I always fool with the fronts because one front sprocket tooth usually equals 6 rear sprocket teeth. Plus, when you go bigger on the front sprocket, the chain runs cooler because its "turn" is less acute. That's no shiz.

HP-wise, your only option is engine modification. That's going to be intake (carbs, reeds, porting), exhaust, or lightening/balancing the internals. A dynamically balanced, knife-edged, cryogenically treated crank and piston assembly will give you a biggest results if you keep the same bore and stroke. On the other hand, that's going to be expensive as hell, and you could just hog the thing out a few cc's. Bore it, stroke it, nothing new- you only get HP the same way it's been gotten for years.

If you combine more displacement with blueprinting the engine (and balancing) the thing would be too fast to ride. It'd just flip over backward.

if you put a bigger sprocket in the rear it would give it more power, smaller in the rear, you get more speed, you cant have both, you could keep your sprocket that you have on now, and put performance mods on the engine, and you would gain a little bit of power, and a little bit of speed.

smaller rear = more power on top = more MPH
Big rear = more power on botton = more acceleration

The fronts do the opposite.