I've got an inconsistent carburetor problem on my '77 - 250: When the motor is at running temperature, it will die on me at idle. If you look at the choke plate, it is fully open and cannot be closed by hand. If I put my hand over the barrel, the idle improves big-time. What is making the choke stick and unable to close, even partially? Overall the car idles great, with or without the A/C going, but every once and a while it does this. (One out of three trips, say). I'm getting tired of throwing the car in Neutral and riding the gas at traffic lights! Thanks for any input.
Choke Problem These carbs are notorious for coming loose at the mounting flange or the screws in the air horn to main body. This allows air to be sucked in and cause a lean condition, putting your hand over the top richens up the mixture. I am not sure the choke is at fault, should close only on cold start and full accellerator depressed. Then the auto choke mechanism should open it as the engine warms up and hold it open through the fast idle linkage. Could be a problem with a vacumm leak somewhere else too. Maybe choke adjustment or heat tube damage? Just a thought on it.
You have a vacuum leak somewhere. Spray carb cleaner around the base and air horn and any vacuum fittings. If the idle picks up, there is your leak. Fix it and you will idle again. The choke will seem locked open if you try to close it manually without opening the throttle. The idle speed adjustment screw prevents it from moving if you don't crack the throttle. That's normal.
