What causes a saw to run hot?

[MS290man]

What causes a saw to run hot? I know if the mixture is too lean you can burn it up but I have never seen this kind of a condition that I found in this 048. It looks like the piston underside got really hot and the skirt failed. Would bad seals cause something like this to happen? This saw looks like it has hardly any hours on it.

 

[jacob j.]

Water in the fuel can sometimes do that but looking at the condition of the cylinder I'm thinking stale/bad gas because it looks like there was still some lubricating qualities to it. The cylinder has a lot of carbon which I've seen in engines consistently run on low quality or old gas.

 

[dall]

i have a 461 im working on did the same thing

 

[Al Smith]

Due to the fact it's an 048 it has some age . By the looks of things it has ingested a huge amount of fine wood dust which,mixed with oil/fuel will pyrolite inside the crankcase .In other words turn to petroleum coke .Another factor being 042-048 air filters are very hard to find so it likely was operated with a bad filter .If it was coke that explains the chewed up exhaust side of the piston having carbon from the exhaust port gnawing away at it .

 

[Lone Wolf]

Due to the fact it's an 048 it has some age . By the looks of things it has ingested a huge amount of fine wood dust which,mixed with oil/fuel will pyrolite inside the crankcase .In other words turn to petroleum coke .Another factor being 042-048 air filters are very hard to find so it likely was operated with a bad filter .If it was coke that explains the chewed up exhaust side of the piston having carbon from the exhaust port gnawing away at it .

I think you might be right Al, that's what it looks like. Although I can't tell if that is the intake side of the piston or exhaust?

 

[Fruecrue]

I would venture to say that's the exhaust side, judging by the blackened deposits on the bottom view, and I see no ring gaps.

 

[dall]

mine broke on the exhaust side and took out the flange under the piston

 

[mnmdad]

YOU GOTS TO RUN RED ARMOR OIL then all problems go away!But ya gotta pull the jug every 1/2 tank to check the piston!!!!

 

[backhoelover]

look like it might have been a little lean too but i could be wrong. did you happen to check for a air leak before pulling

 

[backhoelover]

cylinder

 

[TJ the Chainsaw Mechanic]

Saw runs hot if:
mixture is to lean(low or high side)
high octane fuel
dirt built up in the cooling fins on the flywheel or cylinder
dull chain
dirt build up on the starter cover
dirt build up on the air filter
air leak
probably more things

 

[Keith Gandy]

YOU GOTS TO RUN RED ARMOR OIL then all problems go away!But ya gotta pull the jug every 1/2 tank to check the piston!!!!

 

[dall]

unwatching this *f-wording oil thread

 

[Keith Gandy]

Water in the fuel can sometimes do that but looking at the condition of the cylinder I'm thinking stale/bad gas because it looks like there was still some lubricating qualities to it. The cylinder has a lot of carbon which I've seen in engines consistently run on low quality or old gas.

Ive seen several that color internally but didnt know what was goin on? I figured bad oil but Als explanation makes sense

 

[MS290man]

Saw runs hot if:
mixture is to lean(low or high side)
high octane fuel
dirt built up in the cooling fins on the flywheel or cylinder
dull chain
dirt build up on the starter cover
dirt build up on the air filter
air leak
probably more things

Saw is ultra clean so dirt isn't an issue. I'm hoping it's not an air leak.

 

[Keith Gandy]

Saw is ultra clean so dirt isn't an issue. I'm hoping it's not an air leak.

But all the discoloration and dirty look wouldnt be from just an air leak I wouldnt think? Very odd

 

[fossil]

You would do well to change the seals just due to age. It's worth the effort on old saws and they will generally run better and start easier with new seals. It's cheap insurance.

 

[jake wells]

YOU GOTS TO RUN RED ARMOR OIL then all problems go away!But ya gotta pull the jug every 1/2 tank to check the piston!!!!

bullchit.

 

[jake wells]

wrong heat range spark plug will make one run to hot also along with lean mix bad seals and phase separated gas.
saws don't like it when they get a swig of ethanol mixed with water.

 

[jake wells]

high octane gas wont make a saw run hot because 93 burns cooler than 87.