Each carburetor system has a different jet size when it comes from the factory, but the goal of a stock carb is to operate at or near sea level. This is the standard for carburetor manufacturing, whether the carb is installed on a motorcycle or auto. As the operating altitude increases by 2,000 feet, the amount of air available for the engine will decrease. To compensate for this decrease in air and maintain a proper air fuel mixture, the jet sizes will need to be reduced.
Unbolt the carburetor bowl bolts from the metering block. The metering block is the section of carburetor between the bowl and the main body of the carb where the throttle bores are positioned. The metering block is where the jets are positioned. Pull the bowl off of the metering block and keep the gasket. The jets are now accessible.
Remove the jets with a flat head screwdriver or pliers and note their size stamped on the heads. The jets are made of brass, and there is a hole through the center of each one.
Screw in a new set of jets that are a smaller size (by one or two numbers) than the jets you removed. If you're dropping 2,000 feet or more in altitude, you'll need to increase the jet size by one or two increments. With the new jets installed, press the gasket to the rim of the metering block and press the fuel bowl against the gasket. Screw in and tighten the bowl bolts to complete the re-jetting process.
