Ah.. nice idea!
I did the same thing on my pedal gokart. Coincidence or not - also with the same engine!
I assume your sprocket is around 70 - 80 teeth? I think I used a 72teeth sprocket on my gokart. The engine didn't have that much torque for a fast takeoff. But once you're driving, it can go around 20 - 30km/h.
If you have any questions, don't hesite to contact me. Goodluck!