I have a stock 80cc with a 44t sprocket and weigh 195. I live in Asheville N.C. which is all mountains. I can hit 31 mph on the flats. What suprised me was that I can consistantly hit 22mph on the Blue Ridge Parkway , which is fairly steep. I dont normally run that fast but cruise up the hills at 18mph. I use a synthetic oil that contains castor oil and run a 20:1 mixture since I only have 250 miles on it. I just did the speed tests since it hit 200 miles.