Often asked: How Do You Identify Carburetor Jets?

How do I know what jets to put in my carb?

The old jets will have a number on the side of them to tell you how large the hole for the gas is. If you’re trying to give your engine more gas, install jets with a larger number which means it has a bigger hole. To make your engine run leaner, install jets with a smaller number and therefore with smaller holes.

What are the different carb jets?

Main Jet – this controls the fuel when you open up the throttle (between 50 and 100 percent power) Jet Needle – this controls the fuel when you open and close the throttle (between 20 and 80 percent power) Needle Jet – this is what the jet needle pops in and out of (between 15 to 60 percent of throttle.

Are all carb jets the same?

Yeah, most Keihin jets are interchangeable and most Mikuni jets are interchangeable (though the two brands are not interchangeable with eachother). Any motorcycle dealer should be able to get jets for your bike even if they do not sell the brand of bike you have.

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How do I know what size jet I need?

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.

What is worse running rich or lean?

Running lean can give you more power but to lean will blow your engine. Running too rich can also hurt your motor. Think of it when you are mixing gas for your weed wacker. It is always safe to add a little more oil than not enough to the mixture.

Can you drill out carb jets?

By drilling out your stock main jet to larger sizes you will be able to narrow down what jet size your carburetor needs. You will need a numbered drill bit set. If it’s lean and you need to increase the size of your main jet, drill the jet out with the next size larger drill bit, which in this case is the #60 bit.

What is the pilot jet in a carburetor?

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 raising the needle jet do?

Raising the needle by lowering the chip position at the top of the needle will richen the mixture. Lowering the needle will lean the mixture. WIDE OPEN THROTTLE: Changing the MAIN JET affects this range. Select the size which offers the best wide open throttle.

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Are carb jets marked?

Jets are threaded and have a small orifice through their center that varies based on the size of the jet. For example, a jet may be stamped (on its head) with the number 30.

How do you identify Keihin Jets?

Look on the jets for a number (which is the size of the jet) and the manufacturer ID stamp. them which is a “square within a square” on them: GENUINE KEIHIN jets will have a “K star” stamping on them: Below are different types of jets, look for one that is similar and check measurements to verify it is your jet.

How do I identify my Keihin carburetor?

Find the serial number near the bottom of the CDK carburetor. Write the number down. Call one of the distributors listed on the keihin-us.com website and give them your serial number. Distributors keep track of serial numbers and will be able to identify your particular carburetor.

What happens if main jet is too big?

For example, using too large of a main jet will cause more fuel to enter the combustion chamber than it can efficiently burn. This will result in a “sputter” at full throttle. It could best be described as a rapid misfire.

How do I know if my carburetor is rich or lean?

Q: How Do You Tell if a Carburetor Is Rich or Lean? A: One way to tell for sure is by “reading” the spark plugs. If the plug tip is white, the mixture is lean. If it’s brown or black, it’s rich.

What happens if main jet is too small?

Be careful: most engine jams occur when the main jet is too small. A lean fuel/air mixture will cause the engine to overheat fast.

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