I have a 1995 Specialized StumpJumper FS, with a 2009 50cc gas motor conversion. I built this in 2009 for fun but I never use it. It’s in my garage collecting dust. I’ve only run one full tank of fuel through it. It holds a half of a gallon and has a range of about 45 miles on the tank (90 mpg). The bike will run about 36 mph, with the baffle taken out of the muffler and about 30+ with it in. I also put a leather spring saddle on the bike.