I actually do use an IR thermometer on friction points and bearing surfaces on many of the pieces of equipment I own and operate as 20-30 degree differences are harder to determine.On this saw however the difference was SO SIGNIFICANT that a test of that sort was pointless.When the heat of the cat equipped muffler scorches the saws adjacient plastic cladding and you can feel it heating up your left hand as you operate the saw you know it's to hot.What were the parameters of your test?Was it a cold or hot day?How long did you run the saw?How long did you run the saw under load?What was the nature of the wood you were cutting(hardwood,softwood,species)?I bought a brand new saw and cut aprx 10 cord of wood in a about a three week time frame.Ran several Gallons of gas through said saw before I voided the warranty and cut out the cat.
why would would it matter if it was a cold day or hot day or what size/type wood?
The adjacent plastic on a cat equipped saw is melted due to the extra heat of the exhaust gas. Awhile back another member tested this and the exhaust temperature was much higher on the cat equipped saw. This however, does not directly translate into the engine running hotter. My test was done on a 87 degree day with high humidity. I warmed the saw and made about 10-15 cuts. I bought a used saw with a cat muffler (359) and wanted to see just how hot that baby would get. The cut was done in a 20" chunk of pine and I measured the cylinder and the muffler with a fluke IR thermometer. The front of the muffler was around 400, the cat plate was around 700, and the top of the cylinder was 300. The transfer covers measured considerably less I don't remember exactly. Within a few seconds, the cylinder dropped to 250. Within about 15-20 seconds, it dropped to around 190. The saw was turning 9000-10000 RPMs in the cut. I don't remember the exact temp of the non cat 359 I tested before because I expected the difference to be much greater than it was. Regardless of wood type, I would bet that any saw turning 9-10,000 in a cut for a duration of 15-20 seconds in that kind of weather would measure fairly close regardless if it had a cat muffler or not. Most of the heat is generated by the friction and RPM.
Westcoaster,
Fuel does cool the engine because it can not turn to vapor without absorbing heat. The fins on the cylinder are there to help carry/dissipate the heat.
Yukon
I have no idea why you mentioned the fins on the flywheel.