Chainsaw dying at full throttle

[TheBigDog]

Chainsaw starts a dream, runs well up to 3/4 throttle, then bogs down and dies at full throttle. Replaced fuel line, and cleaned carby out carby, adjusted high and low too.

Spraying engine starter fluid into carby makes it work at full throttle for a minute or so before dying again.

Any ideas? Cheers

 

[sliceoflife]

Fuel cap/tank vent clogged maybe? Cant let enough air in to prevent a vacuum slowing fuel delivery at wot? Just a guess.


Other than that I'd look at carb, fuel pump diaphragm maybe?

 

[pioneerguy600]

A loose or cracked impulse line will cause this also, the engine is running out of fuel.

 

[Big_Eddy]

Or a plugged fuel filter, cracked or pinched fuel line, or plugged screens in the carb.

 

[Orange Ripper]

A loose or cracked impulse line will cause this also, te engine is running out of fuel.

I second this,
the impulse grommet on my 55 I recently serviced was running like the OP mentioned, would run good till about 3/4 throttle but then scream and lean right out up top and then bog and quit, turned out being a massive air leak at the impulse grommet. Although it could be anywhere along your intake tract that had a seal too I believe.

 

[Okie]

You need to quit spraying the starter fluid.
Your starter fluid probably has no lube/mix.

What is the make and model of your saw????

 

[Sidecarflip]

My only comment is... Anyone who uses starting fluid on ANY 2 stroke engine is brain dead.

 

[EchoRomeoCharlie]

You're already seeing a lean condition (bad for engine for several reasons, heat, lack of lubrication, etc) and spraying starter fluid into the engine means it's running longer with even less oil. So stop doing that.

Previous posters have suggested numerous possible causes, troubleshoot or fix those things first, most of them are cheap depending on exactly what model you have. Hopefully you haven't caused significant damage to the cylinder/piston by running it on starter fluid too much.

 

[stihltech]

Do the diagnosis as mentioned above. Unless you would rather get a cylinder and piston.

 

[Vintage Engine Repairs]

it may be a stuck main nozzle check valve or stiff fuel pump diaphragm.