Carburetor - Fast idle too high, then no start

[elspanishgeek]

Hey y'all,

I've continued go-kart testing the Roadster and after a few laps this morning and once the car was nice and warm, I adjusted the curb idle screw on my Holley 600 CFM (since I was running idle at around 1100 RPM) and brought it down to around 950 ~ 1000. From all the research it seems it should still be lower so went to make another adjustment and test drive this evening, however, when I turned the car on I was at around 2900 RPM right at the start. I turned the screw out but I wasn't seeing any effect. I turned off the car, took off the air filter, and found that the fast idle arm was stuck? (Red arm in the pictures). I moved the choke plate a bit and the linkage "caught" back into the arm. I noticed that if I pulled the throttle cable a bit then the choke plate would respond based on the adjustments of the curb idle screw. I went to start the car again but now it was a no go. 2 pumps of the throttle. Nothing. Tried another start and nothing. Turned the curb idle screw in and tried again but still nothing. Figured I'd stop here before I flooded the engine (which I know is a thing but wouldn't know how to tell if it was flooded).

Any recommendations on what I could do here?

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Unrelated, but the test drive this morning was actually with forum member RoadRacer, who was incredibly generous with his time and patience, coming over with his alignment tools and teaching me how to use them for a front alignment. Also, let me borrow them so I can do the rear this week.

[Norm B]

Try this procedure to start your car from cold.
Press the gas pedal all the way to the floor once and release it.
With your foot off the gas pedal, turn on the ignition and start the car.
If you find the initial high idle too high blip the throttle immediately.
As the engine warms up, blip the throttle occasionally to step down the high idle.

When the engine is fully warmed set your idle with the screw you moved earlier. The high idle is not adjusted with this screw.
In most cases the high/cold idle does not need adjustment but, if it does the screw for it is on the other side of the carb behind the electric choke.
Note the electric choke does not sense engine temperature and may need to be set to match how fast your engine warms and to match your normal temperatures in your area. That is different procedure than just adjusting the idle screw.
If you turn on the ignition before setting the choke with the gas pedal you will defeat the choke.

Norm

[rthomas98]

One more item. If you are going to be playing with the fast idle screw the engine must be cold when doing it. If it is hot or even warm, leave it alone. I really recommend watching the below it really helps with figuring out the carb choke and idles.

[CraigS]

When you go to first start the engine cold, you push the gas to the floor once right? This will set the choke closed. It will also let the little red thing move so that as you come off the gas pedal the carb will be held open slightly so you have the higher cold idle. If you just let the engine warm up w/o touching the gas pedal, the choke plate will slowly open to vertical but the little red thing will still hold the high idle. As long as the red thing is holding a higher idle, the normal idle screw has no effect. As the engine warms up, if the gas pedal is moved that releases the red thing to rotate some. Usually the red thing has a couple of steps in it, so the high idle will drop down in stages as the engine warms and the pedal is moved (like as you normally drive out of your neighborhood). The lever that rests on the red thing usually has a small screw in it so you can adjust the high cold idle speed separately from the normal warm idle. It is usually very hard to see, and to access. And it may need an allen wrench rather than a flat screw driver.

[Railroad]

Little Red thing- fast idle cam
Screw on little red thing, fast idle cam adjustment screw.
I have seen new carbs with the fast idle cam screw too tight. It will drag on the cam and not release as it should.
Correction for this, is to loosen the fast idle cam screw about 1/4 to 1/2 turn.
Make sure your electrical feed to the auto choke cover stays fed after you let off the key. Should stay positive while engine is running.

[CraigS]

Great point that I had not thought of Railroad.