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My MS170 would not start. Put in a new plug and have spark. Still no start. Tried starting fluid still no start. Figured carb was bad as saw is 10 years
or so old. New carb from dealer. Now it will start and run for 15 seconds then will not restart for at least 1/2 hour. Gas is new.

Thanks for any help.

Are you using 93 octane gasoline with Stihl brand 2 cycle oil? Also inspect air filter.
Notice manual below states minimum octane rating of 89 or engine overheating & internal damage can occur, thus a higher octane rating will keep engine running cooler. That is why I run 93 octane gas in everything including vehicle. My 25 year old Husqvarna chainsaw states a minimum of 91 octane gas.

Your manual states to use 89 octane fuel and 50:1 oil mix on page 32 below.


Do you have fresh fuel and oil mix?

Are the fuel lines and fuel filter in the tank 10 years old? Might be time for new hoses.

Fuel filter might be clogged. Make sure you shake your fuel can well before filling your tank. I've seen guys with boats have a ton of oil inside their tank sitting on the bottom.

Is your exhaust spark arrester clogged? Remove the muffler and throw that spark arrestor screen away. Unless you are logging in a forest, leave it in. Simple home owner can leave the screen out no problems.

slomo

Yeah, examine the fuel line, they develop cracks. The also can get soft and gummy, and collapse and pinch together.

First thing to do is replace the fuel tank vent part number 0747 313 6810. Replace the fuel line 1130 358 7701. Replace fuel filter part number 0000 350 3500. After those are replaced see if the problem persists.
89 octane regular fuel will work fine just be sure to empty it and run it dry for off season storage.

Hammermechanicman said:

First thing to do is replace the fuel tank vent part number 0747 313 6810. Replace the fuel line 1130 358 7701. Replace fuel filter part number 0000 350 3500. After those are replaced see if the problem persists.
89 octane regular fuel will work fine just be sure to empty it and run it dry for off season storage.

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I used to run my gear dry for the winter, no fuel. I started having fuel line and tank issues the next spring. Lines would dry out, get hard and crack with no fuel.

Now I run Stabil year round. No more issues since. Never had an issue till I started draining tanks and running dry. Those 2 stroke carb diaphragms will dry out on you with no fuel in them.

Maybe my lines were due for replacement? One fuel tank on a trimmer was $180 to repair.

slomo

slomo said:

I used to run my gear dry for the winter, no fuel. I started having fuel line and tank issues the next spring. Lines would dry out, get hard and crack with no fuel.

Now I run Stabil year round. No more issues since. Never had an issue till I started draining tanks and running dry. Those 2 stroke carb diaphragms will dry out on you with no fuel in them.

Maybe my lines were due for replacement? One fuel tank on a trimmer was $180 to repair.

slomo

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