Where is the mixture screw

Yes, they DO affect an "off-idle" mixture a tiny bit, so if your engine has a slight stumble right when you start to crack-open the throttle and you know you are getting an ample squirt from the accelerator pump, then sometimes cracking-open the idle mixture screws another quarter to half turn "can" make that stumble go away, but not in all incidences. The ONLY way you can "really" lean-out or richen-up a carb from the outside is if you have a customized carb with a "Dial-a-Jet" system, on it, otherwise you have to open-up the carb and swap the main jets out to either a larger or smaller size.

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How to adjust the mixture screws on your carb This is an easy one. Site Map. Log in or Sign up. Yamaha XS Forum. Having trouble logging in? Try closing your browser and re-opening it. If that doesn't work, try a different browser or device. The site will be updated soon to resolve these browser issues. Enjoy XS Consider making a donation to help support the site. Login Problems? Tags: carburetors. Mar 5, 1. Screwing the idle stop screw in increases the air flow to both cylinders, which creates more vacuum, which sucks more gas in, which makes the engine run faster.

Now to syncing: Idle the bike at RPM. Place your hands a few inches from each exhaust. The exhaust pressure you feel should be equal. If the right exhaust feels weak, then screw the sync screw in -- this only increases the flow of gas to the right cylinder, remember?

Re-set the idle to , check again, and do a final sync adjustment if necessary. If the left side exhaust was the one that felt weak, you do the same thing, except you screw the sync screw OUT, decreasing the flow of the gas to the right-side cylinder until the exhaust pressure from both exhausts feels the same. Re-set the idle to , check again, and do a final sync screw adjustment if necessary.

The XS is not a space ship, and this does just as good a job as a manometer for all practical purposes. Some people like to sync at a higher idle, such as or even RPM.

That's fine by me, but there really shouldn't be much difference. Now go to the right-side carb and screw the mixture screw in in half-turn increments until the engine starts running slower. Now, turn the mix screw out in half turn increments. The engine should speed up again, and then maybe go faster, but eventually it will start running slower again. The correct mix screw setting is the place where the engine runs the fastest.

When you think you are there, you can check and fine-tune by turning the screw in quarter-turn increments. Keep in mind that slightly rich erring on the screw being more turned out is better than slightly lean. Repeat for the left side. You are welcome to complicate the above procedure by pulling a plug wire points only!

I can hear the RPM changes just fine with both cylinders firing. Don't-over-think this stuff or stress yourself out or be afraid of doing them. They ARE necessary, so be sure to spend the 60 seconds it takes to do them and then get on with your life.

DogBunny , Mar 5, Adamc and snoosky like this. Mar 5, 2. The dead cylinder method seems to have a dedicated following but I never use it either. I can hear just fine what my mix screw adjustments are doing with both cylinders running. You usually find a "range" of maybe a half turn where the motor idles fastest. I set to the rich side of that range.

That seems to help alleviate popping out the exhausts on decel better. Adamc likes this. Mar 5, 3. Great post! No account yet? Create an account. Edit this Article. We use cookies to make wikiHow great. By using our site, you agree to our cookie policy. Cookie Settings. Learn why people trust wikiHow. Download Article Explore this Article parts. Things You'll Need. Related Articles. Part 1. All rights reserved.

This image may not be used by other entities without the express written consent of wikiHow, Inc. Start the engine and let it run for 5 minutes to warm it up. Turn the key in the ignition to start the engine. Warm up the engine to normal operating temperature by letting it idle for about 5 minutes. Keep the engine running after it warms up. Note that this process is the same for any type of engine with an air fuel mixture screw.

It could be a car, motorcycle, scooter, ATV, or anything else with a carburetor. Look at the engine and spot the round or cone-shaped air filter. The carburetor is the part of the engine that the air filter is attached to.

It usually sits on top of the carburetor. On a motorcycle, the air filter usually comes off the side of the engine and faces the rear of the bike.

Find the flat-headed, slotted, gold-colored brass screw on the carburetor. Look at all the different screws on the carburetor until you spot the gold one with a flat slotted head. This is the air fuel mixture screw. Part 2. Turn the screw clockwise until the engine starts to sound rough. Use a flathead screwdriver to tighten the screw. Tightening the screw is also called making the fuel mixture leaner, which lowers the RPMs at which the engine idles.

If you ever want to start fresh, turn the screw clockwise until it is lightly seated, then back it out about 2 turns. Then you can make adjustments from this position. Home information. Part 1 of Start the engine and let it run for 5 minutes to warm it up. Turn the key in the ignition to start the engine. Let it idle for at least 5 minutes so it warms up to normal operating temperature. It could be a car, motorcycle, scooter, ATV, or anything else with a carburetor.