74 CJ5 carburetor replacement I258

I know there are a lot of topics on this but I'm a bit confused. Some say keep it others say replace. I've got a carter YF 643lS on my 74 CJ5 It seems to run alright in warm weather but now that it's cold as H*#l here in Iowa (-9 tonight) it will start the first time then not again till it's completely cooled down again. Also it runs like crap while driving it in cold weather. So I guess what I'm wondering is what to do. It's been rebuilt (2 years ago). Do I replace with something oh 37 years newer or try to rebuild/tweak it???? Any ideas or suggestions are appreciated in advance.


On a side note i also have a YF7001S sitting in the garage off a donor 73.

 

Just offhand, it sounds like it's too lean for the cold and only starts when the choke is on. When it's warmed up and the choke is off, it might not be getting enough fuel for the temp conditions you're running in. If it was me, I'd tear it apart and look for junk blocking the various passages, that could make all the difference in the world.
From what I've read here in the past, that model carb is OK when clean and set-up correctly.

 

This carburetor is a Carter YF. As carbs go, it's a good one. AFAIK there's nothing about the YF that would make it run badly in cold weather, compared to any other carburetor.

So, agreeing with Rick, IMO you may as well try to fix this carb as opposed to changing to a different carburetor. As Rick mentions, you may be set up too lean, ot the choke could be wildly out of adjustment. The choke is supposed to open when the intake manifold is warm enough so that the fuel stays atomized/vaporized and does not condense out on the manifold. I suggest you 1) make sure you have no vacuum leaks, 2) put the factory air cleaner back with its TAC (thermostatic air cleaner) system - this will help cold weather running and prevent icing, and 3) adjust the choke cover so that the choke is only fully open when the engine is up to temperature.

I presume you are running a 195 degree thermostat? And that the heat riser flap is free so that the exhaust gases will warm the intake manifold in cold weather?

 

Well I have found that the only way to get it "restarted" when it's cold is to remove the air cleaner and hold the butterfly all the way open while cranking. I just tore the automatic choke apart and gave it a good tooth brush/carb cleaner cleaning. I guess I'll see if this helped I also adjusted the butterfly so it's a bit more open so i hopefully don't need to manually do it when I drive it in the cold weather. Thankfully (well maybe not) this isn't my daily driver so if it comes down to it I can park till spring and drive the JK.

On the automatic chokes do I just adjust the round block type thing on the fire wall side of the carb to adjust rich to lean????

I believe I just saw that writing on there when I had it out. How do I figure out where I need to be??? So many questions so limited on my knowledge.....:?