YF Fast Idle Carb Adjustment

Any advice on adjusting the fast idle screw on a carter YF 2100 without a tach? I've never really adjusted this part of a carb before. I know I wasn't suppose to touch it but it just didn't sound right.
It seems like it runs the best when black smoke is coming out, but I know thats too rich. So I've been trying to back out the screw to right before the black smoke comes out, even though it dosn't sound as strong. Any advice on a technique? I am assuming clockwise gives it more gas, couter clockwise gives it more air?

 

Are you talking about the idle screw or the mixture screw? Thgey are two different animals.

You need to coordinate them together, aiming to get a smooth idle mix at a reasonable idle rpm. One affects the other.

Peter

 

I believe on most carbs that clockwise leans it out (less gas, more air), and counterclockwise richens it (more gas, less air, = black smoke and rough idle). I might be wrong though.

Been a long time, but it seems like I remember you turn the idle mixture screw in until it runs smoothest, then back it up 1/4 turn. Then adjust your idle speed screw to get the idle RPM you want.

I know you don't want an engine to run as lean as possible, that creates excessive heat that can burn plugs and valves. It's better for it to be a little rich, that keeps it cooler.

 

Ummm...the gold one at the base. It kinda points toward the [assenger seat. I though it was the idle mixture screw?

 

That's probably the idle mixture screw/jet. The fast idle adjustment is usually part of the throttle linkage, it opens/closes the throttle plate just a little.

 

Close but backwards.

Clockwise push the screw in more and allows less fuel. Conterclockwise push the screw back letting more fuel. I learned this the hard way.

Generally lean out until stall, then turn counterclockwise 1 1/4 turns and should be set.

Of course there are tons of variables. Like vaccum. Like me if you have nothing pulling vaccum ( Brake Booster, Emiission) it never works 100%.

 

with my carter i ajusted the screw till i got the higest rpms by ear and then leaned it out just a little bit from there.

 

That's what I said, not backwards!

 

Turning it clockwise makes the smoke black tho?