Main Jets, for Mikuni Carburetors

There is a large amount of horsepower to be gained in a properly tuned carburetor. Unfortunately, there isn't a universal setup that will work with every engine combination. If you have to play with your choke to get the engine to accelerate, you likely need to re-jet. Jetting that works great with one engine may not work so well with another. Stock 22mm Mikuni Carbs come with a 95 or 100 main jet and 15 pilot jet. Install the carburetor and run it with this stock setup. Remove the spark plug. If the plug looks white, your carb is running lean. Try going to a larger main jet. Check the plug again until you get a good light brown plug. Shut the engine down quickly without letting the engine idle, to ensure you get an accurate check. Many racers like the 130 main jet, 12.5 pilot jet, needle clip in the center position and air screw two turns out (stock position). Some run up to the 180 main jet when using a larger Intake Manifold. Results may vary. With the Mikuni correctly tuned, your engine will come alive in both top end and low end torque and acceleration as well as a very responsive throttle.