The gear ratio on your mini bike or go kart is the ratio between the number of teeth on the clutch, and the number of teeth on the drive axle sprocket.
One of the most common gear ratios for go karts is 11-12 teeth on the clutch sprocket, and 60 teeth on the axle sprocket. A very common mini bike ratio is 11-12 teeth on the clutch, and 72 teeth on the axle sprocket.
To find the gear ratio, simply divide the axle teeth by the clutch teeth.
For example:60 on the axle divided by 12 on the clutch = 5.
However,80 on the axle divided by 16 on the clutch also = 5.
Both of these sprocket combinations would result in the same performance on your kart!
As the gear ratio decreases, you can get a better top speed. However, you sacrifice power.
Think about how easy it is to start pedalling a mountain bike in 1st gear. That’s a very high ratio, meaning the gear up front is small, and the gear in the back is big. So your feet (your engine!) can easily produce a lot of power for a hill, but you won’t be able to go very fast.