The size of the carb has nothing to do with it. You will first have to determine if anything is leaking, Fuel lines, fuel pump, carb, fittings, hoses, filter, manifold, gas tank, wrong gas cap, vapor lines or internal dripping, as mentioned... need to find out where the "smell" is coming from, may not be carb. 800 smelled, 650 smelled. Be sure that there is no more than 6PSI pressure, as I said. Too big of a carb does not cause leaks (if there is a leak), just bad gas mileage and performance.
