mixture screw confusion
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Road Captain
Joined: May 2006
Posts: 720
Likes: 2
From: Kansas
mixture screw confusion
hey guys, I've been reading the carb tuning sections for hours and cannot find a difinitive answer,
so which is it on the mixture screw, turning the screw IN (clockwise) is leaner or richer??
here are a couple of quotes I found from the self help sections;
"If you are reading to rich, you may need to lean out the pilot jet or close the screw slightly."
" OFF IDLE to 1/4 THROTTLE: The SLOW JET and AIR SCREW are most effective in this range When you want a richer mixture use a larger SLOW JET or turn the AIR SCREW in. The opposite holds true for a leaner mixture"
please help!! these statements seem to contradict each other....
Thanks,
K.
so which is it on the mixture screw, turning the screw IN (clockwise) is leaner or richer??
here are a couple of quotes I found from the self help sections;
"If you are reading to rich, you may need to lean out the pilot jet or close the screw slightly."
" OFF IDLE to 1/4 THROTTLE: The SLOW JET and AIR SCREW are most effective in this range When you want a richer mixture use a larger SLOW JET or turn the AIR SCREW in. The opposite holds true for a leaner mixture"
please help!! these statements seem to contradict each other....
Thanks,
K.
Advanced
Joined: Jan 2006
Posts: 66
Likes: 0
From:
RE: mixture screw confusion
I don’t know if I can help make this clearer but I will try.......
There are three types of ajustments that can change the idle air fuel ratio.
During idle, manifold vacuum pulls a mixture of air and fuel from the pilot circuit through the mixture screw into the intake just past the throttle plate. The pilot circuit contains a combination of air and fuel. It is mostly fuel with some air mixed with it to help vaporize the fuel. Screwing the mixture screw in restricts the pilot circuit. This reduces mostly fuel that enters the intake and leans the air entering the cylinder.
Remember the pilot circuit is putting a combination mostly gas with some air into the intake. This combination then mixes with the air coming in the intake to make up the overall air/fuel ratio. With the mixture screw I controlled the flow of the pilot circuit to lean or richen the overall mixture. I can also change the air/fuel ratio of the pilot circuit to lean or richen the overall mixture entering the cylinder.
An air bleed screw controls the amount of air in the pilot circuit. Opening it up causes more air in the pilot circuit and less fuel, leaning the overall mixture.
The pilot jet (or slow jet) controls the amount of fuel being introduced into the pilot circuit. Opening it up causes a higher ratio of fuel in the pilot circuit, richening the overall mixture.
Hope this helps……
Doug
There are three types of ajustments that can change the idle air fuel ratio.
During idle, manifold vacuum pulls a mixture of air and fuel from the pilot circuit through the mixture screw into the intake just past the throttle plate. The pilot circuit contains a combination of air and fuel. It is mostly fuel with some air mixed with it to help vaporize the fuel. Screwing the mixture screw in restricts the pilot circuit. This reduces mostly fuel that enters the intake and leans the air entering the cylinder.
Remember the pilot circuit is putting a combination mostly gas with some air into the intake. This combination then mixes with the air coming in the intake to make up the overall air/fuel ratio. With the mixture screw I controlled the flow of the pilot circuit to lean or richen the overall mixture. I can also change the air/fuel ratio of the pilot circuit to lean or richen the overall mixture entering the cylinder.
An air bleed screw controls the amount of air in the pilot circuit. Opening it up causes more air in the pilot circuit and less fuel, leaning the overall mixture.
The pilot jet (or slow jet) controls the amount of fuel being introduced into the pilot circuit. Opening it up causes a higher ratio of fuel in the pilot circuit, richening the overall mixture.
Hope this helps……
Doug
Tourer
Joined: Nov 2005
Posts: 396
Likes: 1
From: Cypress, Texas
RE: SIMPLE ANSWER
(1) Turning the screw "IN" towards the seat will "LEAN" the mixture. Less fuel more air.
(2) Turning the screw "OUT" away from the seat will "RICHEN" the mixture. More fuel less air.
(3) If you install a larger Pilot (slow) jet and do not touch the air screw it will be richer. More fuel.
(2) Turning the screw "OUT" away from the seat will "RICHEN" the mixture. More fuel less air.
(3) If you install a larger Pilot (slow) jet and do not touch the air screw it will be richer. More fuel.
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