Stock gearing on most is 14/41, but that's about right on mph. I had a 16 tooth front on a piped Bansee, and it went 84 mph on pavement, gps. It took forever to get there, though. As a rule of thumb, I think it's 6 mph for each additional tooth on the front sprocket, providing the engine can pull the higher gear. 16 was too much, really