scroll down a little on the page to see the bike video. http://wiley-davis.com/ He explains that "it uses a 35cc 4-stroke engine and a driveline geared to work with my pedaling cadence of 100rpm. I designed and built the bike from scratch out of brass-brazed 4130. So far he has around 1200 touring miles on the bike and says that "it gets anywhere from 200-300mpg depending on load and terrain. Recently, he rode it from San Diego to Las Vegas in two and a half days while towing a 50lb trailer.