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Tom Wesenberg · 08-18-2011, 04:21 AM

See Bratton's 2011 parts catalog page 62 for an exploded view of the carb. #11 is the IDLE SPEED ADJUSTMENT SCREW. This screw should be turned in enough to keep the throttle plate from binding in the bore, and enough to let the engine idle at about 500 RPM.

#5 is the IDLE MIXTURE SCREW, and this screw controls the amount of AIR that mixes with the gas at idle. This is opposite how most other carbs operate. Most other carbs use this screw to control the flow of gas at idle. So, on the Model A turning this screw OUT will admit more AIR and make the mixture LEANER.

08-18-2011, 04:21 AM	#5
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Rough Idle/Stalling See Bratton's 2011 parts catalog page 62 for an exploded view of the carb. #11 is the IDLE SPEED ADJUSTMENT SCREW. This screw should be turned in enough to keep the throttle plate from binding in the bore, and enough to let the engine idle at about 500 RPM. #5 is the IDLE MIXTURE SCREW, and this screw controls the amount of AIR that mixes with the gas at idle. This is opposite how most other carbs operate. Most other carbs use this screw to control the flow of gas at idle. So, on the Model A turning this screw OUT will admit more AIR and make the mixture LEANER.