Jetting is one of the most important elements of a racing engine. Optimum performance can only be achieved with accurate jetting regardless of the extent of modification. We have put together this jetting database from what works best with our bikes with VP C12 race fuel (mixed 32:1 for two strokes) at sea level and 80 degrees. We have listed these specs to assist riders and mechanics with initial reference. Engines will run slightly different with special fuels, weather conditions or modifications so these starting points may not be the best final selection for your engine. Incorrect jetting can typically be characterized with as a bog, miss, sputter, pop or cut-out.
Jetting refers to the fuel metering adjustments in the carburetor. The adjustable circuits on most two strokes include an air screw, pilot jet, needle, needle position and main jet. The adjustable four stroke carb circuits refer to the fuel screw, pilot jet, air jet, accelerator pump, needle, needle position and main jet.
*NOTE- Be aware that lean jetting can cause damage to expensive parts of an engine. Carburetor tuning should be done by a professional that can diagnose a rich or lean condition.