What would you change on the jetting on an 01 RM 125 to make it run better in the cold whether? It is running like crap, it runs like the choke is on but it's not. It smokes bad and has no power, just bogs when you gas it.
It's hard to tell from your post what needs to be done. Generally, colder temperature requires richer jetting, but when you say it runs like the choke is on that sounds like it needs leaner jetting. Are you getting a lot of rain along with the cooler temperatures? Try dropping your jet needle one position and see what happens. Also, be sure your air filter is clean and only lightly oiled.
I get the same thing when it turns cold outside. Theres more moisture in the air so it actually requires LEANER jetting in some cases. It's not what I'd expect, but hey whatever makes the bike run right.