Carbon on 2 stroke piston..

[lilspenny]

I have a Stihl fs94r trimmer that has a carbon buildup on the piston crown. What can I use to safely dissolve this carbon without disassembly?

 

[hacskaroly]

I have a Stihl fs94r trimmer that has a carbon buildup on the piston crown. What can I use to safely dissolve this carbon without disassembly?

You can use Seafoam. You can put some directly on the top of the piston and let it soak. I also put some in the gas tank with the fuel to help as the saw runs. When I do take a top end off, I can usually clean any carbon buildup off of the piston (even thick stuff) within a couple of minutes with Seafoam and a green scotchbrite pad. I could let it soak a little, but am impatient, but would let it soak if just dropping it on top of a piston in a cylinder. No need to do anything special to get it out, when ready, just run the saw as normal.

 

[fredx]

Easiest way I would think is to run a few tanks of quality non ethanol fuel with Red Armor. There are quite a number of folks that have shown that red armor will clean up carbon from piston , ports & exhaust filter screens

 

[Sloughfoot]

What @hacskaroly said if you want fast results. Repeat till satisfied.

 

[bucketofguts]

Don't look at the top of the piston. . If the screen is still on the exhaust make sure it is clean. It needs to run high revs most of the time. I don't run and additives but my saw man does and has been for many years Seafoam has been in his tank. National Champion Snowmobile racer from up north. Reckon you could check your valves. Have a nice day.

 

[lilspenny]

You can use Seafoam. You can put some directly on the top of the piston and let it soak. I also put some in the gas tank with the fuel to help as the saw runs. When I do take a top end off, I can usually clean any carbon buildup off of the piston (even thick stuff) within a couple of minutes with Seafoam and a green scotchbrite pad. I could let it soak a little, but am impatient, but would let it soak if just dropping it on top of a piston in a cylinder. No need to do anything special to get it out, when ready, just run the saw as normal.

10-4, I won't be pulling the engine apart but I can soak it. I've use Quicksilver Power Tune which is of a similar nature, and it helps. The carbon is not a big issue but I'm gonna give the trimmer to a kid so I'm giving it a cleanup. The screen is out and has been since I took it out of commercial service. Red Armor is in it now but without seafoam. I'll add some to the gas. Thanks.