Correct thermoquad choke setting

[73LemonTwist]

I am looking for information/advice regarding setting the fast idle screw position on a thermoquad for cold starts. Neither the shop manual or the carb rebuild instructions are explicit on this - at least not that I can find.

Some carb adjustments are made with the fast idle screw on the top step/cam, and some are made with the fast idle screw set on the second step, tight against the first step. All of these are done with the choke thermostat disconnected so that linkage moves freely.

The question is, once you connect the choke thermostat rod to the carb, where do you want the fast idle screw to end up for cold starts? Should it sit on the first step of the fast idle cam, or on the 2nd step tight against first step transition?

Or alternatively, does anyone know the correct lenght of the choke rod (above the housing)?

thanks folks...

 

[Jonas Nordstrom]

I set it on second step tight against first step.
On this step I adjust the fast idle so that the rpms are high enough to start smoothly but doesnt go crazy.
(On my engine its 1500 rpms.)

Im on vacation now so cant take pics but the choke rod setting should be measured from the carb base.
There are instructions out there though some are tricky to follow.

 

[73LemonTwist]

I set it on second step tight against first step.
On this step I adjust the fast idle so that the rpms are high enough to start smoothly but doesnt go crazy.
(On my engine its 1500 rpms.)

Im on vacation now so cant take pics but the choke rod setting should be measured from the carb base.
There are instructions out there though some are tricky to follow.

Thanks Jonas... I gave your setup a try and it seems to be working quite well at this point. I discovered that the bimetallic coil in the choke was rotating up to 1/4 turn on the mounting post, leading to inconsistent choke rod position. Since I fixed that issue, your setup has been working well for me.

 

[toolmanmike]

Second or third step shouldn't matter unless you have the choke set real light and it won't get to the 3rd step. As long as you hit one or the other and your fast idle speed is in the ballpark. If you set the screw too high on the second step, it might not come down to curb idle when the choke comes off. A basic understanding of how the system works and a little common sense is all you really need. Same goes with choke adjustment and choke pull off's.

 

[73LemonTwist]

Second or third step shouldn't matter unless you have the choke set real light and it won't get to the 3rd step. As long as you hit one or the other and your fast idle speed is in the ballpark. If you set the screw too high on the second step, it might not come down to curb idle when the choke comes off. A basic understanding of how the system works and a little common sense is all you really need. Same goes with choke adjustment and choke pull off's.

Previously was setting the choke to set on the top step, then the vacuum pulloff would bring it down so far it would likely stall. Setting up on the 2nd step cures that issue as there isn't such a large change between step 2 and the vacuum pulldown position (which on my carb sets up on step 3).

Curb idle is fine - never as issue there, but I have experienced what happens if you go too far with the fast idle setting...