MS170 Issue

[Dacha]

Thing on top of oil and gas tank is vent

 

[Michael E]

But can you send pic of which hole I am trying to line up.

The carb is mated to the intake boot on the back of the carburetor. A big opening lets the fuel/air mix from the carb into the engine. In the intake manifold there is a second, tiny opening. The engine acts like a air pump when the piston is going up and down, sending air through the impuls opening to the carb. This air operates the fuel pump side of the carb. Igf this tiny hole in the intake boot and the tiny hole in the carburetor housing don't line up or the surfaces don't seal properly, the fuel pump does not work.

Google "ms 170 intake boot" and look at the pretty pictures, it is very easy to see. On other saws, there is a separate rubber hose, which can fail.

The tank vent can keep the saw from running, but only after some running time. When the fuel level drops and air can't enter the tank, you get a vacuum. But not on the first pull.

Don't blame Stihl, the MS 170 is a solid little saw, usually very reliable.

 

[LAtree]

Problem solved. I expected it being a fuel issue. When fuel line is pushed into tank. If it is not at exact angle right above filter line bends and collapses line. My fix was I pulled line and cut a good half inch off. Seems to start fine now. My guess others have same issue. My saw sits a lot and bend appears to have deformed the fuel line.

 

[SteveSr]

My understanding is no impulse line. So I have no idea how it is designed

The impulse goes through the main manifold through a small hole.