Stihl FS 55RC Smoking

Hi all. We've had our FS 55RC weed whip for a number of years (since 2004, I believe). It has always struggled to run properly, so it sat dormant for quite a few of those years. We've rebuilt the carburetor, taken it to small engine repair places, etc, but nothing seemed to keep it going... until I recently discovered premixed fuel at one of the big box stores.

A couple weeks ago, I bought a container of TruFuel 50:1 premixed fuel (ethanol free) to try out... and our weed whip worked! For the first time in years, I was able to go around the yard and easily take care of problem areas.

Today, though, while I tried to use the weed whip, the engine started smoking a light gray / white smoke. I read in a couple spots that it could be from a wrong mixture of oil to fuel, or it could be from too much ethanol. Since I bought this premixed, I'm assuming (hopefully correctly) that it is a 50:1 mixture. And the can states that it is ethanol free fuel.

Anyone have ideas as to why it might have been smoking?

I'm giving the weed whip a rest, but if possible, I'd like to finish the yard today. Obviously I don't want to do that if there's a chance I'll ruin the engine.

Thanks in advance.

-Joel

I would take out the air filter and give it a good cleaning in Dawn dishwashing soap/hot water, and check your muffler screen for carbon fouling, as dirty air filters will cause rich running and carbon buildup.

It takes a 5/8 socket to remove the muffler tube.

Thanks for the help, @Fish. I gave the Stihl a good onceover and didn't see any problems, so I decided to press on. Since we recently switched from regular gas from the gas station (with oil and stabilizer) to the canned gas, I thought I'd see if maybe it was just burning off some excess junk from the old gas.

I ran it around our yard for a good 40 minutes. It worked like a champ. And after the smoke cleared (which wasn't very long), I didn't see anything from the week whip that was concerning.

Thanks again for your help. I appreciate it!

-Joel

FWIW the oil in 2 stroke mix can & does come out of suspension under crankshaft pressure.
As such it will build up in the crankcase, which is a good thing.
On mowers it just sits on the lower bearing but on trimmers it gets sloshed around so ends up in the combustion chamber.