Stihl MS291 won't run when hot

[Leisurephile]

I have a 4 yr old MS291 that fells and bucks 25-30 trees/yr. I run only non-ethanol 91 and Stihl oil. Ran saw yesterday for the first time this year, fell and bucked one tree, cutting second tree, saw was good and warm and sputtered out. I could get it to start, but not run, would die under throttle and at idle rpm's would drop until shutoff. Opened fuel cap and replaced, no change. Cleaned air filter w/ gas, replaced while still moist, started and saw ran fine until filter dried, making me think it was a fuel delivery issue. Checked spark plug, was a nice medium brown. Fuel filter looks fine. Sat overnight started and ran fine to start, adjusted carby, same condition appeared.

Questions:

-Anybody had same issue and found a fix?
-Has anyone had a leak in manifold boot on newer Stihl?
-Would a fuel delivery issue appear only when hot?
-Would a hot coil have an intermittent issue?
-Would a hot coil with an intermittent issue consistently start then die?

Any help is appreciated!!

 

[HarleyT]

Go through the carb and fuel system. Throw out your old fuel.

 

[Leisurephile]

Has new fuel in it. What in the fuel system would malfunction only with heat?

 

[HarleyT]

Well, take off the muffler and peek at the piston too.

 

[Wood Doctor]

Sounds like a low-compression issue. I think that's why HarleyT said to remove the muffler and examine the rings and piston. Of course, I could be wrong. You can get a clue by holding the saw with the starter handle and letting it fall. If it drops down on its own, compression is low. Some saws might run if it does fall, but most Stihls will not.

I believe that processing 120 trees is pretty good service for a Farm Boss. It's not a professional saw.

 

[Billy mcvay]

Low compression on my 291 when it get hot it want do nothing could it be the rings and if so are they hard to put the saw ain't but a month and a half old this is the second one I done got and it did the same thing as the first one get hot want crank pull cord the saw hits the ground but can take the plug out put a little oil in it and sometimes it crank and sometimes it don't

 

[J D]

Low compression on my 291 when it get hot it want do nothing could it be the rings and if so are they hard to put the saw ain't but a month and a half old this is the second one I done got and it did the same thing as the first one get hot want crank pull cord the saw hits the ground but can take the plug out put a little oil in it and sometimes it crank and sometimes it don't

Sounds like your toasting top ends. With a relatively new saw that would likely be a lean tune, poor quality or a lack of oil, or pushing the saw with a dull chain.
On a side note this thread is nearly 5 years old