Is my Stihl FS111R running hot or not?

[ueww40]

I just recently replaced the short block and piston (4180 020 1209) on my trimmer (nothing wrong with the old one, except that the valve seats were shot and can't be replaced by themselves. The engine purrs and runs like a new one (which it is) but I feel it's running hotter than before or maybe it's not and I am just paranoid. On top of that after about half hour of trimming all of a sudden the engine stops, which it never did before. My question is this. Do 4 mix engines have built in overheat protection or is it something else that cuts off the engine. Since I am still breaking her in I am taking it easy with the trimming, but it is summer time and it's hot outside. Like to hear your thoughts on this. Thanks

 

[Creaky limb tree care]

It's probably fine. Just a new engine hot smell

 

[ueww40]

It's probably fine. Just a new engine hot smell

OK, thanks

 

[hacskaroly]

My question is this. Do 4 mix engines have built in overheat protection or is it something else that cuts off the engine.

No, the 4-Mix engines do not have built in overheat protection (no sensor or anything like that). If it is not catastrophic failure like a scored piston and cylinder or an air leak, its generally a break in the fuel/air/fire cycle. I have a FS 91 and have had it occasionally cut out, but it starts right back up. When it does that, gives a quick chance to check fuel and string load anyway.

 

[ueww40]

Thanks for the info about the overheat protection or lack thereof. In that case it might be the ignition coil going flaky at a certain temperature. Not a big deal. I will keep an eye on it and do some testing when it happens