Quick Answer: How To Set Carburetor On Yamaha 450 Quad For Altitude?

How do you adjust the carburetor on a Yamaha ATV?

Look for the black idle adjustment knob attached to a cable on the left side of the carburetor. Turn the adjustment knob clockwise to increase the idle speed, or counterclockwise to decrease the idle speed, as needed to bring the idle speed to between 1,450 and 1,550 rpm.

What does adjusting the needle in a carb do?

Within the needle jet the needle moves up and down to vary the orifice size to meter the fuel. The tapered shape of the needle controls the amount of fuel coming up through the main jet and through the needle jet. As it goes up, the opening gets larger, letting more fuel into the mix.

How do you adjust a running rich carburetor?

Regardless of whether or not the engine is running too rich or too lean, bring it down to a very lean mixture by turning both screws a quarter-turn at a time, counter-clockwise, then slowly bringing them back up to an equal and smooth mixture.

How do you know if your ATV is running lean or rich?

A black dry fluffy colored plug is caused by deposits from a carburetor that is running too rich (too much gas), or excessive idling on some engines. Black smoke coming from the exhaust is a sign of a rich air/fuel mixture.

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Why is my four wheeler sputtering?

There are many reasons why an ATV sputters. The most common reason has to do with a carburetor problem like a tuning issue, vacuum leak, or gas leak. Other sputtering issues can be caused by an ignition issue. For the combustion chamber to work on an ATV, it needs air, gas, and a spark.

How do you adjust the air fuel mixture on an ATV?

Make adjustments 1/2 a turn in either direction to find the smoothest idle speed. Turn the screw counterclockwise and clockwise 1/2 a turn from the middle position and listen to the sound of the idle. Set the screw in the position where the engine’s idle sounds most even and smooth to balance the fuel mixture.

Does needle position affect idle?

The needle position has no affect on idle, it basically affects mixture around the 1/2 throttle range. If you need to change the WOT mixture you need to change the main jet, then change the needle to suit half throttle needs.

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

If the pilot circuit is rich, the engine will have a rough idle or may not return to idle without “blipping” the throttle. You may also notice a distinct smell of raw fuel and some eye irritation from the exhaust.

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