CARB ADJUSTMENT?

colt 1911

Active Member
#1
JUST SWAPED OUT CARBS ON A PEDATOR 212. THE ORIGINAL CARB DID NOT HAVE THE ADJUSTMENT SCREW CIRCLED IN THE PICTURE. WHAT IS THE CORRECT ADJUSTMENT PROCEDURE FOR THE SCREW? THANKS JEFF s-l1600 (4).jpg
 

SAS289

Well-Known Member
#2
I would run it as is unless you want to fine tune the idle mixture. You would warm up the engine, get a tach on it with the idle around 1600 or so set by the plastic idle speed screw. Then turn the pilot screw in or out looking for the highest RPM. Backing out is more fuel, turning in is less fuel. And if there's not much of a change in RPM, then what, a larger pilot jet? Maybe. If you do find the highest RPM leave it there and then set the RPM you want with the plastic idle speed screw.

In my opinion I could care less about the idle mixture because I don't let my engines sit around idling. The low speed circuit still provides fuel off idle but how much more or less fuel can you get with the screw? Some will go to a larger pilot jet if they want more fuel from that circuit.

I recently took a stock carb and removed the non adjustable screw and bored the venturi larger for a 224. I used a .037" main and a .018" pilot jet. I set the pilot screw 1 1/2 turns out. I didn't bother with fine tuning because it idles well enough. Stock pilot jets are around .016".
 

colt 1911

Active Member
#3
I would run it as is unless you want to fine tune the idle mixture. You would warm up the engine, get a tach on it with the idle around 1600 or so set by the plastic idle speed screw. Then turn the pilot screw in or out looking for the highest RPM. Backing out is more fuel, turning in is less fuel. And if there's not much of a change in RPM, then what, a larger pilot jet? Maybe. If you do find the highest RPM leave it there and then set the RPM you want with the plastic idle speed screw.

In my opinion I could care less about the idle mixture because I don't let my engines sit around idling. The low speed circuit still provides fuel off idle but how much more or less fuel can you get with the screw? Some will go to a larger pilot jet if they want more fuel from that circuit.

I recently took a stock carb and removed the non adjustable screw and bored the venturi larger for a 224. I used a .037" main and a .018" pilot jet. I set the pilot screw 1 1/2 turns out. I didn't bother with fine tuning because it idles well enough. Stock pilot jets are around .016".
thanks for the help. at a minimum this video gave a description of what it controlled Carburetor Animation - YouTube
 
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