Re: 80cc bike engine has no power :(
Sounds like a carb problem Twaddles, could be the float is not letting enough fuel to fill the bowl up. Could also be dirt in carb, at idle there is enough gas but when you need more gas, it can't deliver it fast enough and it bogs out. Did you use a fuel filter?
I would not even start mine without one, the gas tanks are nasty on the inside.