Hello, my 1985 GS sat for over six months after I purchased it from someone who let it sit for 4 months after they bought it. The seller to me didn't know how long it sat before he purchased it. It did not billow white smoke when I bought it. I changed the oil, rebuilt the carb, replaced spark plugs, and I'm at a point where I think the fuel filter for clogged with bad gas because the engine cranks but does not start. What is peculiar is that prior to discovering I cannot start the engine, I put 2 gallons of fresh gas and earlier in the day before putting fresh gas in I started it and drove it for 15min. It had its problems but they improved with each lap around my block. Btw that drive was done with 6 month old gas in the tank. It billows enough white smoke for 10 min on startup to make neighbors come out and check what's up. My coolant level has not dropped and the coolant itself in the radiator looks like plain old coolant. If my coolant level isn't dropping at all and I'm billowing white smoke for 10 min on startup what could be the issue? My car ceased to smoke after driving it for that 15 minutes but 4-5 hours later when I started it again it billowed the same amount. This is when it started sputtering and I let it die because flooring the accelerator could barely keep the engine alive.
The engine also wants to stall without the choke engaged and has been like that since I purchased it. My gut feeling is that the fuel is bad and the carbs idle speed/mixture is off. My idle is at 1k with the choke engaged and I have to give gas to keep from stalling with the choke disengaged.

 

White smoke normally is a sign of coolant, let it sit and pull the plugs and see if they are wet with antifreeze

#1 mistake you did was rebuild the carb without draining the old gas, you may have to clean it again cause old gas does numbers on a carb and fuel system

 

The next time you drive it shut it down and pull the spark plugs. Check for moisture. After a hot run the spark plug holes will steam heavily if there is coolant seal breach.

 

White smoke could be oil or coolant, you have to smell it.

I would first go through the fuel system completely:

1. Empty tank (FBs have a drain plug at the bottom)
2. Replace any rubber hoses that seem questionable (replace all if you want to be sure)
3. Replace filter
4. Make sure hard lines are clear.
5. Check fuel flow at carb to see if you are getting good gas and enough of it
6. Now see if it starts after deflood procedure of your choice to get the plugs dry

If you see a lot smoke on startup and it goes away it could be old oil seals that are dry and hard from sitting. If
it is it will correct itself over time usually. If it smells like coolant then you can try some collant additives like
AlumaSeal which have worked for others in the past.

 

+1 on the alumaseal. It did the trick for my FB.

 

This happened to my 85 gs after only 2 weeks of sitting. After the 3rd drive it went away, so now I just don't let it sit for more than 5 days. Took the plugs out after the first time and they were not wet, so still don't know what it was.

 

If the smoke does smell like antifreeze, take the intake manifold off and check the coolant seals there first before using any type of alumaseal.

 

Im having the same issue sort of. Mines smokes on the 1st initial start for like 10 mins. If I drive for like 20 mins and shut off the car, then start it in like 5 mins later it throws out a huge cloud of smoke then it clears up. I think I may have bad water seals. Which Alumaseal have you guys used?

 

One thing that helps is to use thicker oil. Could be your oil seals are worn.

 

If you have a bad oil control ring, thicker oil = thicker smoke. The experience I had with my s5 with bad oil control rings was 10w30 put out a good puff on a cold start, but went away in seconds and stayed away. Where 20w50 took longer to quit smoking , and was thicker smoke. I tried 20w50 with Lucas oil stabilizer and holy crap! Mount ST Helens on a cold start, and an almost Cheech and Chong like haze throughout the whole drive. Something about the thermostat in the iron that controlled the amount of smoke on startup.