You can also determine if you need to jet the carb based on how the bike rides. If your dirt bike tends to be sluggish when you punch it and/or backfires when you open it up a bit, you're probably too rich. However, if your bike can take off in a sprint but lacks overall power, then you've got too much air.
The carburetor consists of four components: Which you can learn more about in this video Carburetor Operation
- Pilot Jet - this controls the amount of fuel when idling
- Main Jet - this controls the fuel when you open up the throttle (half to full throttle)
- Jet Needle - this controls the fuel when you open and close the throttle (off idle to about half throttle)
- Needle Jet - this is what the jet needle moves in and out of during operation (off idle to about 3/4 throttle)