M runs uneven at idle

[Rod51M]

Just started my M up for the first time in about 10 months after some restoration. Would never have gotten to this point without a lot of help from many of you, so I want to thank you all.

Now that I buttered you up, here is another question. At idle, it will stall or run very unevenly unless I give it a good bit of choke, even whent the engine is hot. I noticed a lot of condensation on the upper part of the carburator and it is very cold to the touch. Is that normal? Don't know if that is a clue or not? I did not have the carb apart but I don't remember this problem previously. I have to run it at about 2/3 throttle for it to run evenly without any choke.

thanks,
Rod
 

[MisterT]

It is normal, and in cool weather with high humidity it will even form frost and sometimes even ice. What you SEE happening on the outside is also happening on the INSIDE, and that's why the engine runs rough and stunbles. There are several work-arounds and cures for it, but the best method is to just do whatever is needed to keep it running long enough for the engine to warm up, and then the problem usually will go away.
 

[The Red]

Open up your idle mixture screw a full turn and see if that helps. If not, that tiny idle tube might be partially plugged.
 

[Wayne in MN]

Turn the idle mixture screw IN for richness; it is an AIR adjusting screw on those carburetors.
 

[Rod51M]

Thanks guys. It is running smooth now. I had to turn it in and make it richer - almost 3/4 of a turn. Idled beautifully and then I took it out on the road and ran it wide open for a bit and it still sounded good. I really appreciate the help!