What is main jet and pilot jet?

What is main jet and pilot jet?

The main jet controls the amount of fuel when you’re at about 80% to a wide-open throttle. The pilot jet controls the fuel level when you’re at idle to roughly 20% throttle. The jet needle controls the fuel level when you’re between 20% and 80% throttle.

Does pilot jet affect Main Jet?

The pilot jet typically can deliver no more than 15% of the overall fuel when the throttle is wide open. The claim of 15% is based upon the inside diameter of the pilot jet and the inside diameter of the main jet. The air screw, as you probably know, will effect mixture at idle primarily.

What does the main jet do on a carb?

The main jet provides the fuel at 80 percent to wide-open throttle. The fuel flows up and out through the needle jet into the throat of the carburetor. When changes in air density are significant the main jet will need to be swapped. Handling the mixture between the pilot and main is the needle jet and needle.

What do pilot jet numbers mean?

For example, a jet may be stamped (on its head) with the number 30. This indicates that the jet’s size is 30 mm. Installing a smaller size jet will reduce fuel flow, which is ideal for high-altitude conditions where air is limited, where a larger jet size increases fuel flow for oxygen-rich, low altitudes.

Does main jet affect idle?

The main jet does not effect the jetting for starting and idling. It plays no part on low RPM or mid RPM jetting either. The main jet is very important to your machines overall tuning, but should never be over emphasized at the expense of needle tuning or other facets of your carburetion tuning.

What does changing the pilot jet do?

Changing the main jet size will adjust the top end of the operating range from half to full throttle. Adjusting the needle jet size, jet needle, and needle clip position will affect the mid range operation. This leaves the pilot jet size and the pilot screw for the idle and low throttle conditions.