I have a 3.5 hp mini bike that runs great. My question is, if i put a bigger sprocket on the engine shaft and a smaller sprocket on the axle, will the mini bike go faster? Will it be too hard to start up? Any other suggestions on how to make it go faster will definitely be appreciated. Thanks!

 

You could go up a tooth or two on the front or go down a few teeth on the rear that will give you more top speed but I would not do both at the same time.
If you want your mini bike to haul butt you need to look into the COMET CLUTCH System. I have one on a goped I made with a 5.0 Briggs and it will go 55Mph all day long and it will hole shot almost any dirt bike in the neighbor hood you won't believe the differance.

 

Also on the mini motors check to make sure when you have the throttle twisted wide open that your linkage is actually pulling the throttle on the carb wide open and if you have the pressure type rev limmiter on that motor you can install a lighter spring on the linkage and it will raise your rev limmiter.