Before we start; I am not interested in flaming Stihl or the chain saw's owner. I use a lot of their products and I just spent $400.00 buying a new 290, but I am curious about this incident and I'm looking for opinions about the possible cause of the failure and Stihl's reasoning. I have a personal opinion about the warranty issue, but it is irrelevant here since the owner accepted the dealer's answer.
A friend has a MS251 that burned a hole through the piston in less than 20 hours of operating time. The saw was new with less than 2 months since purchase when the failure occurred. I know this guy and he takes very good care of his equipment (his previous saw went 20 plus years), so I'm sure it was not a maintenance item beyond what I will describe that caused the failure. He had the proper mix of Stihl brand oil to fuel and the cylinder wall shows zero scoring.
He freely admits that he was trying to get one last cut out of a dull chain and the saw was working hard to do it. He said it felt warm, but obviously not so hot he could not use it.
The dealer refused warranty stating that the saw was just over worked by the dull chain and it overheated. The dealer checked for air leaks into the crankcase which would result in a lean mixture; none found. He never touched the mixture screw on the carb. It started and ran normally until the failure. He subsequently replaced the saw with a new 251.
Is this a result of emissions requirements making the saw run lean? Any other ideas?
#2
ILENGINE
Pre-detonation caused by improper octane fuel, improper timing, or red hot carbon in cylinder. Basically spark knock.
Really sounds like something stihl would take care of. Have your buddy take that saw to another dealer and no need to tell that dealer a back story on what happened. Less is more!
Sounds bogus and against the he- man "steel" image. Only thing I can think of that hasn't been mentioned is an improper (static) installation of the spark module. Recently saw that the modules do advance 22 degrees. In cars over- advance can cause problems. Go cart guys watch carefully exhaust gas temp with probes. Also AC aircraft very concerned.
