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John Butts in CT · 05-23-2013, 03:53 PM

No needle valve will function as designed unless it closes at full CW rotation, and what's more frustrating than an "adjustment" screw or knob that doesn't adjust anything? So... I have four observations to add:

(1) Make sure that both the GAV needle assembly and the idle mixture screw are the correct length and actually do bottom out in the seat (I've seen versions of both that were so short that they "bottomed out" in the threads long before the needle hit the seat.)

(2) Some repro idle mixture screw springs are too long, and also prevent the needle from seating. Try the screw without the spring, see how much space you have for the compressed spring, and cut the spring to fit. Oh, and make sure that the spring collar (ferrule?) is not too deep, as well.

(3) Make sure that both brass needles are polished, true, and free of scoring.

(4) Make sure that both needle seats are clean and smooth.

Running these checks is a fun, easy, and rewarding workbench job. Get it right and you're good to go for your lifetime.

05-23-2013, 03:53 PM	#14
John Butts in CT Senior Member Join Date: May 2010 Location: Southeastern Connecticut Posts: 464	Re: Choke Adjustment Needle? No needle valve will function as designed unless it closes at full CW rotation, and what's more frustrating than an "adjustment" screw or knob that doesn't adjust anything? So... I have four observations to add: (1) Make sure that both the GAV needle assembly and the idle mixture screw are the correct length and actually do bottom out in the seat (I've seen versions of both that were so short that they "bottomed out" in the threads long before the needle hit the seat.) (2) Some repro idle mixture screw springs are too long, and also prevent the needle from seating. Try the screw without the spring, see how much space you have for the compressed spring, and cut the spring to fit. Oh, and make sure that the spring collar (ferrule?) is not too deep, as well. (3) Make sure that both brass needles are polished, true, and free of scoring. (4) Make sure that both needle seats are clean and smooth. Running these checks is a fun, easy, and rewarding workbench job. Get it right and you're good to go for your lifetime.