I was using my Stihl MS 251 chainsaw last weekend helping a friend cut the stumps off a number of small trees and he wanted the cut as close to the ground as possible without getting the bar & chain into the earth. Approaching lunch time and the saw had been working fine all morning without any sign of a problem I turned the saw off. After lunch I went to restart my saw when I immediately noticed virtually no resistance when I pulled the starter cord. The saw was clearly damaged in some way. When I got home I took the muffler off so I could see into the exhaust port. I noticed the piston top appears to be broken around the top circumference and vertical scratch lines along the piston surface so something has obviously damaged the Stihl question what?
The fuel was new, 5 litres unleaded petrol purchased only a few days before, I had mixed one of the Stihl two-stroke 100ml oil cartons sin the petrol container and shaken well so I recon the fuel mix will have been ok.
What I would like to know is if it was a result of me cutting the stumps close to the ground, I could feel the hot exhaust gasses wafting up to me due to the saws close proximity to the ground, and the tree stump and because the saw was on its side the exhaust gasses did not have as much space to escape as they would have had if I was using the saw limbing a branch etc.
Could this have caused the Stihl to overheat and damaged the piston?
The Stihl is just over a year old, and only gets the occasional use so I am hoping the 2-year guarantee will cover the repair. I have not adjusted any carb settings so they are as from the factory, and the saw has always ran well and cuts logs and branches like a hot knife through butter, I always use a sharp chain, so if any experts out there can offer me any advice as to why the piston has become damaged, and why this would result in virtually no compression I would be grateful
