Confusion about Mix screw

[macocoy]

Is turning out the mix screw makes it richer or leaner?I've upgraded to open air filter and tecnigas exhaust
I've taken out the pilot jet to drill a little bigger but the smallest tip cleaner I have won't even fit thru the hole on my stock pilot jet.Can this be just resolve by adjusting mix screw?thanks

[macocoy]

I just called my Dealer today and according to them,if your mix screw is closer to the cylinder it controls fuel flow,and if it's closer to the air box it controls air flow.The idle speed screw assuming more in the mid of carb.

[macocoy]

This is from exriders.com

And lastely, a little bit about the difference between fuel screws and air screws:

Two stoke carbs normally have air screws and four stroke carbs normally have fuel screws. You can tell if a carb has an air screw or a fuel screw by it's location on the carb. An air screw will be on the intake side of the carb while a fuel screw will be on the engine side of the carb.

They sort of work opposite one another. An air screw adjusts how much air is being delivered thru the pilot circuit: in is rich (less air) and out is lean (more air). A fuel screw adjust how much fuel (or air/fuel mixture) is being delivered from the pilot circuit. In is lean (less fuel) and out is rich (more fuel).

[CROSSBOLT]

My experience with carburetors indicates the IDLE adjustment screw controls AIR: screwed IN is LESS air therefore RICH, screwed OUT is MORE air therefore LEAN. The fuel flow is a fixed jet generally with a real small hole. The idle jet is usually the first one to get plugged up when the bike has been sittin' for a long while. All this is irrelevant since you should adjust the idle mix screw for a smooth idle and a smooth transition from idle to opening throttle with no hesitation. Adjust between the points of rich and lean (in and out respectively) where the engine starts to "stumble" or run rough. fine tune to the rich side for the best transition from idle to throttle. Most modern carbs are FIXED and cannot be adjusted thanks to the EPA. These will have a throttle stop screw but no mix screws of any kind.

Karl

[macocoy]

This one from scootersus.com (under assembly)


The Idle Mixture on your brand new Scooter may need to be adjusted when you receive it. The carburetor is adjusted at
the factory (sea level) where the atmospheric conditions may be different than they are in your area. It isn’t difficult for
anyone with a small degree of mechanical aptitude. All you need is a screwdriver and a good set of ears.

The carburetor is located under the right rear fender in front of the rear wheel, attached to the engine. On the side of the
carburetor, you will find two brass screws. The screw located farthest from the engine (on the left as you look at it) is the
AIR/FUEL MIXTURE screw. Turning this screw clockwise RICHENS the mixture with more fuel/less air; turning it counter
clockwise LEANS the mixture with less fuel/more air. The screw closer to the engine at the base of the “tower” is the
IDLE SPEED screw. Turning this screw clockwise INCREASES the idle speed, turning it counter clockwise DECREASES the
idle speed. The next step is to warm up the scooter by riding it around for about ten minutes. When the engine is warmed
up, park it on the centerstand in a well ventilated area, and leave the engine running at idle. With a screwdriver, give the
AIR/FUEL MIXTURE SCREW a quarter turn in whichever direction INCREASES the engine idle speed.

IF turning the screw in either direction causes the Idle speed to DECREASE, that’s it! Set the screw back to it’s original
position, and you’re done. Move on to the IDLE SPEED adjustment. IF turning the mixture screw in one direction or the
other causes the idle speed to INCREASE, continue turning the screw in that direction another QUARTER TURN, and listen
carefully to the engine speed for a few seconds. Continue doing this a quarter turn at a time until you hear the engine idle
speed begin to DECREASE, and return the screw setting to where the engine runs at the fastest idle. As a final touch, give
the screw 1/8th turn clockwise no matter which direction you’ve been turning it (to err on the rich side which runs
cooler). Now, you’re ready to set the IDLE SPEED. Turn the IDLE SPEED screw counter clockwise until the engine sounds
like it wants to stall, then clockwise again about 1/8th to a quarter turn to smooth it out. Your scooter seems happy to
idle at about 1800 to 2000 rpm.

To summarize the process:
1. Warm up the engine.
2. Adjust the AIR/FUEL MIXTURE screw either way for the fastest idle speed, (remember to err on the RICH side by
giving the mixture screw 1/8th turn clockwise from fastest idle).
3. Adjust the IDLE SPEED screw for a normal sounding idle