86 305 idles rough on cold start, ideal when warmed up

[Bonnewagon]

Be glad you have the front mounted one. Some carbs, mostly truck, had only the rear and they suck big time, always hanging up. Cool part is you can set it cold by applying vacuum and seeing it open, then measure and adjust the gap. If it conks out right away, too much. If it chugs, too little.

 

[billyjack]

If you adjust the choke by rotating the black plastic cover, you'll automatically take up any slack as you're pulling the choke closed from the thermostat. Even if you think it's OK, loosen the screws and rotate the cover to verify. I just rechecked the adjustments on my '87 305 with a similar single break stock Q-jet and stock air cleaner. At an ambient temp of about 65 degrees, the choke is just barely closed by the spring tension of the thermostatic coil. As for the vacuum break adjustment, including the free play allowed by both the slop in the rod and the slotted hole in the choke blade lever, it's pulled open 5/32" by the break. As I mentioned in an earlier post, this thing starts quick and runs fine in any season, any temperature. And I'm in Pittsburgh, PA, where we get to experience all four seasons.

Bill

 

[ilduce]

Well you guys got it. I took my ole micrometer out there and my choke was open about a quarter inch when set because of that slop. I did the choke cover adjustment and I could hear all the parts tightening up. I set the choke pull-off to a quarter inch. I started it after a few days later and it didn't take as many pumps. And, it goes to fast idle right away. I like that! Then today after about four days and 20 degrees colder and the same thing. That was a pretty good free tune-up

 

[Bonnewagon]

Thank's for posting the results. It's usually something small causing trouble.