Need Help With A Stihl Saw

Walkin Horse · May 14, 2015

I startedup my MS 390 to cut a log. I ra it for less than a minute when white smoke started coming out of the muffler. It was still running but I cut it off. My first thought was the gas. But it's the same gas I had been using in my Farm Boss. This saw is about 3 y/o. 2 years ago the plug blew out of the head. Still paid for the repair just out of warranty. It doesn't have much time on it. Any thoughts what the smoke is from?

gladehound · May 14, 2015

Is there any chance that bar oil got on the muffler while you were cutting? A few weeks back I was making a horizontal cut in a log with the bar above the muffler. Some bar oil dripped down on the muffler and boy did it smoke!

KiotiKowboy · May 15, 2015

Isn't white smoke a sign the mixture is too lean?

dragoneggs · May 15, 2015

Walkin Horse said:
I startedup my MS 390 to cut a log. I ra it for less than a minute when white smoke started coming out of the muffler. It was still running but I cut it off. My first thought was the gas. But it's the same gas I had been using in my Farm Boss. This saw is about 3 y/o. 2 years ago the plug blew out of the head. Still paid for the repair just out of warranty. It doesn't have much time on it. Any thoughts what the smoke is from?

Yeah that happened to me too. How was the saw running? Smooth?

gladehound said:
Is there any chance that bar oil got on the muffler while you were cutting? A few weeks back I was making a horizontal cut in a log with the bar above the muffler. Some bar oil dripped down on the muffler and boy did it smoke!

My 2 cycle engines tend to puff blueish smoke but I tend to error on too much oil in the mix than not 'enough'.

Sodo · May 15, 2015

Headgasket. The white smoke is steam ( its coolant ).

Just kidding.

Another possibility is the muffler had oil in it and is heating up.
Whats the plug look like? Shine a flashlight into the plug hole, look at the piston top.

Walkin Horse · May 15, 2015

I don't think it's the gas. The 290 is running great. You mentioned oil in the the muffler. When I went to use it it was laying upside down in between two logs where they had rolled around. Some oil may have run out. I guess the thing to do is take the muffler off and clean it. Then fire it up and it will either run or burn.

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Sodo · May 15, 2015

I'd look at the plug and the piston top & if normal, just assume that oil in the muffler will cook out. Probably raw oil from the bottom of the crankcase spilled out into the muffler while it was upside down.

sdef · May 19, 2015

I can't imagine white smoke from a chainsaw unless it is steam from water intrusion somewhere. Both of my Husqvarna's have cut hundreds of trees and the only smoke I have seen is bluish.

crazyal · May 22, 2015

back in the day when I rode motocross the bikes would often do this when cold if they had been sitting for some time. A mechanic told me it was oil that collected in the bottom of the crankcase and as the fresh gas/ oil mixture was going through the engine it would clean the old oil off. He said if you saw it smoking like that don't let the bike idle or it could foul the plug. I never bothered to investigate it but it always went away after the engine ran some.