Here are some basic guidelines for selecting an appropriate gear ratio for your mini-bike or go-kart.
If you are new to using a manual clutch, it is best to start off with a gear ratio that provides good acceleration. Gearing that provides high top speed, commonly referred to as "tall" gearing, can be challenging to get used to for those with limited experience using a manual clutch. Tall gearing requires the clutch to be slipped a lot more to get going which takes skill and practice to accomplish.
Use the chart below to select the appropriate front and rear sprocket sizes based on the style of riding that you will be doing. You need to know your rear tire diameter in order to use this chart effectively. If you have a heavy kart or limited horsepower, lean towards using a larger rear sprocket or a smaller front sprocket.