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Perfect time for a carburetor choke Issue especially since I live in Los Angeles and it's 90 +.
BUT on my 1974 I have a 770 Street Avenger on a 454 HO. When starting the car after sitting overnight I press the accelerator in one time and the choke butterfly closes. Turn the key and the engine roars to life and the RPM's indicate that the choke is functioning as it supposed to for about 2seconds then the RPMS drop and the car sounds as if it is starving for gas I have a poor idle almost stalling for about minute then the RPM's sneak back up to the choke idle speed and I can drive off, Within a short time the choke comes off and I can cruise around happily ever after.
Could it be fuel is leaking from the bowls overnight and during that first start of the day it takes the fuel pump that extra time to refill them. Where would the gas go I have no evidence of gas leaking from the carb plumbing, Any trouble shooting suggestions would be appreciated.
From: At my Bar drinking and wrenching in Lafayette Colorado
Sounds like your choke pulloff is opening the choke either too much or not enough after initial cold start. Once the engine has started, use your fingers and manually change the choke plate angle (opening) to see if your engine requires a different pulloff opening than what the carb is set at. Once you determine the pulloff angle that the engine likes, adjust your choke system to achieve that angle upon engine start.
Lars
OK Choke Pull Off is that adjusted by turning the choke coil cover. The one that you turn to adjust how soon the choke comes off. Would a proper setting be about 1/4 inch opening when the butterfly is in the fully closed position.
Do my symptoms sound as if the choke is coming open too soon?
Those models don't have choke pull offs , maybe tighten the choke thermostat housing a couple of notches , wait until you try it cold before you do any more . If you get it to tight the choke will come on while you visit a store for 5 minutes or gas up even though the engine is hot and cause a whole different problem
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by Dins74
Do my symptoms sound as if the choke is coming open too soon?
Do as I stated: Determine if your choke pulloff is opening the choke too much or too little by changing the choke angle using your finger until best idle is achieved. Then make note if the angle is more or less than your pulloff is producing. Make correction based on those results. I can't guess if it's opening too much or too little - that's why you have to do the test.
Originally Posted by Eric P
Those models don't have choke pull offs
Yes, they do. The choke pulloff is an old, horrible design used since the 1960's. It's a vacuum-actuated piston contained inside the choke housing, and it opens the choke a set amount depending on the resistance applied to the piston (choke housing windup). Vacuum is applied to the one side of the piston from a vacuum passage from the housing piston bore into the carb, and there is a fixed "bleed-off" channel to allow the vacuum to bleed, allowing the pulloff to vary its stroke length depending on the spring resistance of the choke cover.
The Holley choke pulloff is a piston located inside this bore/cylinder inside the choke housing:
OK Mr. lars,. I was out of town three weeks, as soon as I got back I did as you instructed and found that the choke was adjusted closed too much at start-up - it is August in LA - 90 plus outside. On a cold start up the symptoms started. I opened the choke valve with my fingers about a 1/4 inch and immediately the RPM's increased and the idle smoothed out beautifully. Holley has a youtube video on how to make this adjustment which is nothing more than loosing the three choke coil cover screws, hold the throttle wide open, and rotate the coil cover clockwise or counterclockwise for the correct adjustment. There are marks on the carb and coil cover to use for guidance. THE ENGINE MUST BE COLD FOR THIS ADJUSTMENT!
I adjusted my coil cover one notch counterclockwise which opened the choke valve at start - up maybe a 1/4 inch and BAM problem solved.
DISCLAIMER The little instruction on this adjustment was meant for the other greenhorns like me to get pointed in the right direction - . lars I am sure that you are familiar with it.
Thanks for the advice, the choke setting at start-up was not on my trouble shooting radar.
Eric P, I made the adjustment you had described and was only looking for how long the choke stayed on while driving. I was getting some backfiring until the car was completely warmed up. That original adjustment cured my backfiring problem - I guess I over adjusted because it created my start -up problem.
This was a great learning experience that caused me to really study proper carb adjustment.
I stand corrected I had to turn the choke housing clockwise (Lean) one notch for the proper adjustment. On Cold start-up the motor reaches choke idle smoothly. within a minute or so a lil blip of the throttle and it drops down to a nice smooth idle. So far so good.
Choke Issues
