QuestionI have 3 large oak trees (4+ diameter) that I am trying to make firewood of. Trees are on the ground. My 18" poulan was not up to the task so I move up to a Stihl 365. The saw burned out after 2 hours cutting the trunks into 16" sections. The store I bought the saw from claims I didn't have oil in the mixture. I contend that a 50 to 1 mix ratio was inadequate the task and for heavy duty use a much richer mixture should have been advised.
AnswerThis is a tricky one to answer, but I will start with the Fuel Oil Mixture...
50 to 1 mix Ratio in your Stihl 365 is correct. The ole saying of if a little is good a lot is better is WRONG in todays newer saws that recommend 50:1 Ratio. People who add more oil then the manufacturer recommends actually cause all kinds of problems by doing so. Excessive smoking, slow throttle response, plugged exhaust screens just to name a few.
So the answer to this part of your question is 50:1
I dont know if you had oil in your gas or not. But if you did and the service center is saying you did not the reason for their diagnoses is because the failure looks like a lack of lubrication failure.
This is an easy mistake to make when diagnosing a two cycle failure, but they should know how to test the fuel that was in your unit for an oil/gas mixture (Basic Stihl dealer school teaches this and the dealer has to go to become a Stihl dealer)
There are two other things that can cause a failure that looks like lack of lubrication
Is the saw relatively new? If so you may have an air leak. This needs to be determined and is done by doing a pressure test.
Do you have Ethanol in your fuel? How much? Ethanol in the bottom of your fuel tank will get sucked into the carb/cylinder first and burns much hotter then gasoline. This of course is not Stihls fault. This again can be determined by doing an ethanol fuel test. This failure generally has scoring all around the piston. Scoring on the exhaust side indicates lean mixture via an air leak or no oil in the gas.
I hope this helps...
