heres the dill pickel, how hard are you on the throttle? if your at WOT the gas is bound to not last as long, then take into consideration is the bike jetted, it should get better mileage right? you are effectivly putting in a smaller jet to lean the bike, so it should do better on gas, but ive found that my bike with a 158 main in top clip position is way better on gas, than my bike is running with a 155 main in mid clip position, but it runs way better i guess what im trying to say is that so many things come into play the only way to guess mileage is to just ride and see, im sure with stock jetting you should be able to get about 60 miles out of it.:cool: