I've been tuning my carb and have a few ?'s. I had a 157.5 main jet and it had a bog when you took off wide open and it was running lean. I put a 162.5 jet in and it helped the bog and the plug looks good. When it idles its to rich because the plug is jet black. The air screws was 1.5 turns out so I turned it 2.5 turns out now when I stop and take off wide open it bogs the pops threw the carb and finally takes off. I can pull the choke out and it will take off pretty good. Did I turn the air screw out to far and make it lean? You do turn it out to lean it and in to richin it right? Also my clip on the needle is on the 4th notch down.

 

im pretty sure on the 4 strokes turning the screw out will richen it and in will lean it..

 

OH so I went the wrong way and made it even richer. I thought I read a some post where you turn it out to lean it & in to richin must have been for 2 strokes or somthing.

 

Yep you went the wrong way. The way I remember it for my personal taste is 2-stroke carbs turning it in you're "IN"-richening it. And for a 4-stroke carb, turning it in, you're "LEANING INTO IT". Just my way to try & make it easyier to remember.[img]i/expressions/face-icon-small-cool.gif[/img]

 

Yup you made it richer, just remember that if the mixture screw is on the motor side of the carb than your adjusting the fuel flow from the carb to the motor. If the mixture screw is on the air intake box side of the carb then your adjusting the air flow into the carb. So your procedure was correct, it was just for a different carb!!!
If you find you are running the mixture screw too far in then you might have to go to a leaner mixture jet, I think the pilot jet controls that!! Correct me if i'm wrong!!!

 

IDLE MIXTURE SCREW:
The idle mixture screw is the only externally adjustable carburetor jet available and controls up to 1/8 throttle only. There are two types of idle mixture screws. One type is called a fuel screw because it regulates the flow of fuel into the idle circuit. This type of screw is located AHEAD of the carb’s slide tower (motor side) and is most often found under the carb’s bore and upside-down directly ahead of the carb’s float bowl. By turning the screw out you increase the amount of fuel that is allowed to slip around the tapered needle and into the carb’s bore where it is mixed with air that has snuck under the carb’s slide.
If the idle mixture adjustment screw is located BEHIND the carb’s slide tower (airbox side) then the adjusting needle regulates air flow into a fixed flow of fuel intended for idle. By turning this screw inward you are reducing the air flow, thus richening the idle mixture.
When the motor is up to operating temperature, set your idle speed screw to a stable idle. Then use either your idle fuel or air screw to obtain a stable idle. Reset the idle speed screw as necessary after obtaining the correct idle mixture.

Taken from-Hot Horsepower Tips--April 2002
By Greg Hall

 

Thanks for your help. I had it 1.5 turns out and it was real rich how far should I turn it in?

 

I would say no more than 1/8 of a turn at a time. Because what you playing with is for fine tuning, just an 1/8 one way or another could be too far in either direction. So, adjust it VERY little at a time & test run, very little, test run............

 

Well I'm having really weird things going on with my carb. I have adjusted my air screw from 1/2 turns out to 2 1/2 turns out and it pops back threw the carb at every setting. I can put 2 fingers over the snorkle (by the way it has been trimmed down a couple inches for more air) and it will run better or pull the choke out and it runs better but its all ready rich to begin with. I think I have the snorkle cut to much and its not pulling the fuel threw when I put my fingers on it that creates a vacuum to pull the fuel threw am I right? When it sets and ildes for a few seconds it's like it loads up with to much fuel and will barely run untill you clear it out. Please help[img]i/expressions/face-icon-small-frown.gif[/img]

 

I did some test runs and when you stop and let it idle for a few seconds and give it about 3/4 to full trottle it will barely run. Took the carb off and it has fuel every where it has fuel in the back of the carb where the breath hose goes on and in the intake boot it had alot. Pulled the carb out of the intake boot and fuel ran out. So its definetly getting to much fuel. Do I need a smaller Pilot jet it has a 40 in it do I need to go to a 35 or smaller? Please help I'm going nucking futs [img]i/expressions/face-icon-small-disgusted.gif[/img]