Hi there!
Until a few seconds ago I thought I knew the basics of carbs pretty good.
In a thread here I read the you would lean out the mixture when you turn the screw in, and richen it out when you turn it out.
I find this little logical ?.
This is what I have always thought:
If you screw the screw in, the screw will block the air and the "suction" down to the float chamber will be bigger making the engine suck more gas?.
If you screw it out then the channel in the carb will be opened up and more air will be sucked into the engine?.
Gees, have I been wrong all these years?.
Until a few seconds ago I thought I knew the basics of carbs pretty good.
In a thread here I read the you would lean out the mixture when you turn the screw in, and richen it out when you turn it out.
I find this little logical ?.
This is what I have always thought:
If you screw the screw in, the screw will block the air and the "suction" down to the float chamber will be bigger making the engine suck more gas?.
If you screw it out then the channel in the carb will be opened up and more air will be sucked into the engine?.
Gees, have I been wrong all these years?.
WrdAl
New member
Depends on the carb.
If the carb has an air screw, used to adjust the amount of air allowed in, then out is lean and in is rich. Just like you describe above.
But, if the carb has fuel screws, like most Yamahas, then you're adjusting the amount of fuel allowed, then in is lean and out is rich.
If the carb has an air screw, used to adjust the amount of air allowed in, then out is lean and in is rich. Just like you describe above.
But, if the carb has fuel screws, like most Yamahas, then you're adjusting the amount of fuel allowed, then in is lean and out is rich.
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change_up
New member
Yep, WrdAl is right most yamaha's are fuel screws... including your sled, or the other one you are trying to fix (Vmax...right?) To richen you would adjust the screw out more.
A good rule of thumb is when the screws are on the intake side of the carb slide are fuel screws, when they are on the bellside(rear of slide)they are air screws. They work in exact opposites as the fuel screws control the amount of fuel entering the the intake, so the more they are in, the leaner it is as it constricts the fuel opening. The air screws would be the exact opposite by turning them OUT further, they let more air in the circuit thus leaning the mixture.
So, an air screw only adjust the amount of air entering the idle circuit, not gas?.
The fuel screw adjusts the amount of fuel entering the idle circuit?.
So, if I turn the air screw out, the engine will run leaner, as more gas enters the circuit.
If I turn the fuel screw out, mor gas enters the ciruit and makes the engine run richer.
If I turn the air screw in, less air will enter the circuit and the engine will run richer at idle.
If I turn the fuel screw in the engine will run leaner since less gas is entering the circuit.
Gees this is confusing.
What about the dellorto`s on my modified mopeds and the carbs on my dirbikes?. They are in the "middle" of the carb, what are they?. Fuel or air screws?.
The fuel screw adjusts the amount of fuel entering the idle circuit?.
So, if I turn the air screw out, the engine will run leaner, as more gas enters the circuit.
If I turn the fuel screw out, mor gas enters the ciruit and makes the engine run richer.
If I turn the air screw in, less air will enter the circuit and the engine will run richer at idle.
If I turn the fuel screw in the engine will run leaner since less gas is entering the circuit.
Gees this is confusing.
What about the dellorto`s on my modified mopeds and the carbs on my dirbikes?. They are in the "middle" of the carb, what are they?. Fuel or air screws?.
WrdAl
New member
correct, you're controlling the amount of airkimoaj said:
correct, here fuel is being controlledkimoaj said:
more air enters the circuitkimoaj said:
correctkimoaj said:
correctkimoaj said:
correctkimoaj said:
good question, next time they're apart, pull the screw and try spraying some carb cleaner into the screw opening.kimoaj said:
My guess is that if the cleaner comes out somewhere in the air stream it's an air screw. If the cleaner comes out of the bowl or some where that is normally full of fuel, then they're fuel screws.
That would be my assumption anyway.
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