How to Rejet a Dirt Bike By: James Harley Jr

What does the Pilot Jet do? The pilot jet supplies the engine with fuel when idling. When you twist the throttle on the dirt bike giving it gas, the accelerator pump squirts some fuel. As the vacuum slides open, fuel begins to suck through the main jet and mix with fresh air coming in, then you go back to zero throttle. Fuel is then coming through your pilot jet (only enough to make it idle).

Why do you Rejet a Dirt Bike? You rejet a dirt bike because the dirt bike is running rich or lean. Running rich means it is getting to much gas and running lean means it is not getting enough. This will make it run better, if the dirt bike is running to lean the motor will blow up. If it is running to rich the dirt bike will lose power.

Different types of Pilot Jets Pilot jet- idle jet Needle jet- In the barrel of your carburetor. From 1/4 throttle to mid throttle. Main jet- wide open throttle.

The Tear Down to the Pilot Jet Step one: take the seat and number plates off of the bike. Step two: take off the air box and air filter. Step three: take off the clamp to the carburetor, because the pilot jet is in the barrel of the carbueretor. Step four: screw the jet out of the carburetor

Putting the New Pilot Jet in As you were taking the old jet out, and it was 3/4 in, or 2 1/2 turns out, you need to replace your jet. When you put your new jet in, put it in at 1 1/4 turn and that should be the right place for the jet to be at,.

Weather Temperature can play a huge role in how your dirt bike engine runs. As the air temperature rises, the air density becomes lower, causing a richer mixture. To combat the rich condition, you will have to use jet sizes with lower numbers to compensate for lower air density. If barometric pressure decreases, the opposite effect will occur, and you will have to adjust for higher air density with higher jet sizes.

How do I know if a jet is GENUINE MIKUNIE, GENUINE KEIHIN, or generic? What does this mean? The OEM equips a mikuni carb with GENUINE MIKUNI jets and a keihin carb with GENUINE KEIHIN jets. Many providers make generic jets that may not match the genuine jet. GENUINE MIKUNE jets will have stamping on them which is a "square within a square" on them GENUINE KEIHIN jets will have a "k star" stamping on them

What do the Numbers Mean on the jets? The bigger the number is on the jet, the more fuel flows. This also means the bike will run richer. The lower the number is on the jet, the less fuel flows. This also means the bike will run leaner.

What the pilot jet looks like

How the Bike Runs After Being Rejetted After the bike is rejetted it will not run to rich or to lean. The bike will run perfect and will idle without stalling. The bike won't blow out clouds of white smoke from the exhaust. The bike won't hesitate/miss a beat.