My 2002 Honda Shadow VLX 600cc has a modified airbox, drilled out stock exhaust and rejetting for more power. It gets about 45 mpg if I go fast on curvy roads, 55 mpg for normal saner riding on 55 mph speed limit roads with a lot of curves and some stoplights, about 65 mpg at 63 mph for long highways, and drops to about 60 mpg at 75 mph on interstates. It is not really made for 75 mph, but will do it and more- some people have rode these across the country. Stock the top speed is about 95 mph. I have never had mine over 85 mph. The vibration takes a while to get used to.