I have an old 80s yamaha tri moto 125 it really runs rough in the cold.I have cleaned the carb,changed the plug.changed the gas but it still runs rough.Any ideas?

change fuel filter and rebuild carb [by the way to late for the stabil ]

Hi Brandon:
I'd be suspicious that the high speed jet in the carb is plugged, and would suggest that you give the carb a really good cleaning.
Is there a fuel filter?
Is there any chance that you've gotten some contaminated fuel?
Try draining the carb into a glass jar and look for water, dirt, jelly etc. in the gas.

If indeed the carb is clean, it might get "false" air, air after the carb, as the mixture is not rich enough to start when cold. Likely the jets could still b partly plugged... sounds really like a fuel/air problem.

fuel filter clogged or fuel pump problem

Drain out old fuel.put in fresh fuel. Take out spark plug put in little gas and put spark plug back in. try to start.

Sounds like it could be as simple as a fouled plug. Change the spark plug and try it again. Lugging a 125 around fouls plugs really easily, you have to open it up and clean it out occasionally.

try squirting fuel in carb does it fire for a second if this happens

if gas is in the oil the needle and seat in the carb are bad or some thing in it. the gas will go in to the crank case and load the cylinder with gas. you can take the carb apart to see if something is in the seat. or replace the carb

poor tickover is in the pilot circit. does it smooth out at half throttle? what condition do the plugs show after a long tickover?
if you didn't really really clean the carbs (full disassembly, all ports checked for good continuity) then go back and take them apart.