Have seen similar issues with no solid answers.
here’s the scoop.
bought truck, tried to smog (california) failed. Was told by shop carb is failing. Had it sent off and rebuilt.
runs better but still too rich and fails the test again for a CO level of 1.97 (max allowed being 1.20)
at 2500rpm.
brought home changed distributor cap and rotor, fixed timing, adjusted float, new plugs, new wires.
Now it runs the best it’s ever ran! With my hopes I up go to the shop only to FAIL with a CO level of 2.97!!! and labeled as a gross polluter!
1 screw this state.
2 please help.
I’m open to any and all ideas of how to lean my truck out for the test. I’ll attach results of the two tests.
Thank you.

 

What’s also strange is my hydrocarbons shot way up since the last test too. Is this sign of a failing carb? The truck seems to run so smooth with more power than ever so I’m at a total loss.
I was able to get ahold of someone that will let me barrow their stock carb from a passing truck to see if that helps. Even though my carb was JUST fully rebuilt by a shop, I have my suspicions. Will post results

 

You probably have to adjust the air fuel mix adjusting screw. turning it righty-tighty will lean it out. Also look at and replace every single vaccuum line. lceenginnering sells a nice silicone hose set that I had good luck with. Also the oem asian carbs are very reliable but infamous for adjustments. I ended up getting mine rebuilt and two shops and an experienced friend never got it. I got the webber 32/36 kit and never looked back. They also sell a smog legal weber 32/36 kit. That may be worth looking into.

Its considered an false tale but getting the truck properly warmed up and a little of the red bottle HEET (Basically alcohol) seemed to help 22rs pass smog. get the truck to say 1/4 tank of fuel and add two red bottles of heet it helps lower a lot of numbers for the smog in ca.

 

I thought the air fuel mixture screw only adjusts the fuel mixture at idle because the rest of the rpm range is all needle and main jet? Maybe my understanding is wrong.
I’ll be sure to look into these legal webers!

 

As a general rule of thumb for factor air/fuel mix screw settings you turn it all the way in till it bottoms out. Then unscrew 3.5 turns. But here is from the haynes manual for how many turns for the baseline by year:

Heres what my Haynes manual says

Idle Mixture Screw
1979- 1 3/4 turns out
1980- 1 1/2 turns out
1981/82- 2 1/2 turns out
1983- 4 turns out
1984- 4 1/2 turns out
1985 and on- 3 1/2 turns out


While im sure there is more too it you want to check all the vac lines and timing too. The Asian carbs are amazing until something goes out of wack and i just didn't have the patience. The weber 32/36 does has some disadvantages if you have massive elevation changes (requires re-jetting on super high vs super low heights) but in general its not an issue for most 22r owners.

 

From the FSM:



Is this ny help?
It looks like the hardest part of the whole thing is drilling out the plug over the Idle Mixture Adjust screw without trashing the head of the screw.

I don't remember just where I got the FSM from, but it's out there, in PDF. Just do a Google, or whatever you prefer, and you'll find it. Honest! Download it, keep it on your HD, and you can print out any page(s) you need for what you're doing. When you get done, throw them away, or keep them in a binder for next time.

Anywho, good luck to you.
Pat☺