What does the pilot jet do?

The pilot jet handles the mixture from idle to 15 to 20 percent throttle. Air comes in through the front of the carburetor drawing fuel up through the pilot with a vacuum that is created as the air flows through the pilot circuit.

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.

What does a bigger pilot jet do?

A larger jet number means a bigger hole and more fuel. A smaller jet number has smaller holes and should be used if your engine needs to run more lean. Whether your machine is running too lean or too rich is a good starting point for choosing your jets, but using a jet calculator minimizes trial and error later.

What does the Mikuni pilot jet do?

The pilot jet is the part which supplies most of the fuel at low throttle openings. It has a small hole in it which restricts fuel flow though it. Both the pilot air screw and pilot jet affects carburetion from idle to around 1/4 throttle.

What is the function of main jet in the carburetor?

The main jet is responsible for supplying the fuel that mixes with the air as it makes its way through the intake tract after the pilot jet is done doing its job. Starting at about 20 percent throttle the fuel flows through the main jet.

Do you screw pilot jet all the way in?

If your fuel screw is in further than 2 turns, you need a leaner pilot. Off idle heavy feel or sputter. Revving the engine in neutral will result in RPM dip below idle RPM, RPM’s will drop quickly. Turning the fuel screw all the way in will not stall the engine.

What size pilot jet should I use?

How do you tell if your pilot jet is too lean, rich, or just right? The pilot jet is sized correctly if the fuel screw setting falls between 2.5-3 turns out. The pilot jet is sized correctly if the air screw setting falls between 1-2 turns out, with 1.5 being the sweet spot.

How do I know if my pilot jet is too rich?

If your air screw is in further than 1 turn, you need a richer pilot. If your fuel screw is out further than 3 turns, you need a richer pilot. Off idle hesitation or bog. Revving the engine in neutral will result in hanging RPM’s, or RPM’s will slowly drop back to idle RPM.

When should I replace my pilot jet?

Lean symptoms – if the bike surges, carb spits when throttle is opened, exhaust backfires or pops when throttle is closed, or the engine has trouble idling down, engine needs a larger pilot or slow jet to correct. If the engine idles rough, fouls plugs, or is hard to start, pilot is to big, or rich.

How do I know if my pilot jet is too lean?

If the bike surges or hunts, the pilot jet is probably too small (lean). Other indications that the pilot circuit is lean are popping or spitting through the carburetor when the throttle is opened and popping or backfiring through the exhaust when the throttle is shut.