Chainsaws

Fred,

Just a little analysis:

Obviously the bar is getting way too hot, If its turning the metal blue which is also changing the temper of the steel. I have been studying the heating of bars using an Infrared heat gun, I am not sure at what temperature the bar turns blue, typically bars that I have mave noticed after 1 minute of full throttle with no load the chain will heat the bar up to somewhere between 140 - 190 degrees. You definitely would not want to touch a bar after running for a while.

You did not say what length bar you were using, but I have noticed that the shorter bars, ie. 12 " length heat up the fastest and seem to get the hotest, and the longer bars ie. 20 inch stay the coolest, but I have not had a bar turn blue.

Some things to think about: I don't believe there is anyway for the clutch to transfer heat to the chain and then to the bar, however it is important that the chain and chainsaw are running at the proper speed, and yes the clutch or the engine could effect the chain speed.

Next, Its real important that the drive sprocket which the clutch mates with is the proper pitch for the chain pitch, and if the bar has a nose sprocket, that all of these parts are the proper ones to match.

Next, Tension of the chain will definitely cause heat, I have tightened up a chain tight and it causes too much resistance of the chain to the bar, and will heat the bar up fast with no load or Not cutting anything, also the chain should not be too loose or run the risk of the chain coming off the bar, but you do need some looseness.

Finally, And you already stated lubricant oil which reduces the resistance of the chain to the bar is very important. Oh I did not mention that the proper sharpening of the chain will also effect the heating of the bar, because a dull chain has to work harder, and makes smaller chips or sawdust and the operator has a tendency to push harder on the saw.

So here is what I would check: check the drive sprocket, the bar, the nose sprocket, and the chain that everything is a match for the same pitch. If  your Not sure If everything is a match, have a Husqvarna Authorized Dealer look at everything for you.

Next, Check the engine RPM's, and check the speed at which the clutch engages, their should be specs for your specific saw, Typical numbers for my 455 chainsaw are 2800 RPM's idle speed, 3800 clutch engages, and 12,500 RPMs Full throttle at No load. I check mine with a digital tach, which are actually very reasonable today and easy to use for 2 stroke engines. Improper RPM's will definitely cause heating because the chain is not cutting at the proper speed.

Finally double check the chain tension is Not too tight, also a mistake that alot of chainsaw operators make is to adjust the chain slack when the chainsaw is hot," Do not adjust the tension on a hot chainsaw! " Wait till it cools down, give it a good 5-10 minutes after running a hot saw, the links will be loose but this is normal,  when the saw cools down the chain will tighten up, and after it is completely cool check tension.

Oh, and already stated but don't forget the bar oil!

I hope this analysis helps!

PS. A bad clutch will not engage at the proper speed, which will probably mean you have bad or weak clutch springs but, you need to check the speed of engagement.