Stihl MS170 no power

SteveinMo · Dec 16, 2012

Smaller of my two Stihls the MS170 starts right up but has no power. New plug, new filter cleanned out the whole chain and blade safety area.Starts up as soon as you pull the trigger it boggs down and dosen"t want to run at all. I can see only one adjustment screw on the carb and it is not easy to get at. Any help will be greatly appreciated.
Should say other Stihl runs perfectly on same gas and bar oil.

rrlund · Dec 16, 2012

Has it been sitting for a while? Mud wasps like that sweet 2 cycle oil and build nests in the mufflers on 2 cycles when they sit very long. Causes back pressure so they won't rev up.

Just one thought.

JerryS · Dec 16, 2012

Does it act that way with the bar/chain off of the unit? Just wondering if it might be a bar/chain/sprocket issue.

Adirondack case guy · Dec 16, 2012

rrlund,
I think you are on the wright side of the motor. The spark arestor screen could be built up with carbon also.
Loren, the Acg.

JayinNY · Dec 16, 2012

Check the spark arresters screen, first thing I do with any new 2cycle is throw away that screen, some of this new 2cycle junk even get a hole in the muffler so they can breath, I also remove that stupid throttle interlock, or on my saws I tape them down, when I walk with a running saw I lock the chain break, and why do we need a interlock on a string trimmer, hedge clipper ect??! But check your muffler, maybe even look at the exhaust port!

El Toro · Dec 16, 2012

If that carburetor has a neophrene fuel puump it may need replacing. The alcohol will ruin them. I drain my saw after using it and then let
it run until quits. The Stihl dealer in our area told to me to do that on my string trimmer. Hal

Russ from MN · Dec 16, 2012

Have you tried adjusting the carburetor? It sounds like it needs to be opened up a little to compensate for varnish in the jet, very common problem. For non adjustable carburetors I use some Sea-foam.

FBH44 · Dec 16, 2012

Yep, I"ve got one of those, and the plugged-up spark arrestor screen was my problem. Get a propane torch, not anyhting hotter, get the screen off, and burn all the carbon off. Fixed!

Anonymous-0 · Dec 16, 2012

in addition to the muffler screen, check the fuel lines, from the tank to the carb, they tend to get hard, and hairline crack, due to the alkhol in today's fuel!

Mike in Mn. · Dec 16, 2012

The muffler is plugged almost tight, my ms170 did the same thing about two weeks ago, it's only 2 years old, plugged tight, check it out.

Goose · Dec 16, 2012

Not necessarily.

I have a 170 and the owner's manual simply says not to use gasoline with over 10% ethanol.

With chain saws, etc, I never bother to do anything beyond shutting them off when I'm done using them, and they always start right up and run OK when I need them again, whether it's 6 hours or 6 months.

Stihl MS170 no power

SteveinMo

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rrlund

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JerryS

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Adirondack case guy

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JayinNY

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El Toro

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Russ from MN

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FBH44

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Anonymous-0

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Mike in Mn.

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Goose

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