Follow-up to my scored piston issue: Was in contact with a couple dealers. Finally got a cause for a scored piston: over-heating/hot... causes for that include straight gas, worn chain, air leak, etc... Still know that I did not run straight gas. Emptied fuel from saw into jar. Took it to a dealer. he says, well, definitely mixed. it has a green tint to it. talked a bit more and he brought out a known good mixture.mine was "clearer". then I remembered, when I bought the echo, I had to purchase their oil initially for the warranty. thougth it might be a different color than Stihl's. grabbed the bottle and got ready to open than looked at the Stihl bottle. Noticed a little size difference. Then thought Uh-oh... at the top of the stihl bottle it says in regular print "2 cycle Engine oil" at the bottom in larger print with a bigger red "2".. Makes 2 gallons.... I look at the echo bottle and there's a Huge "2" and at the bottom of the "2" in black it says STROKE... in the lower corner in smaller print it says "1 Gallon mix"... oh crap... mixed it and comapred to old mix.. it's darker.. add the extra oil to old mix.. same as new mix.. crud!Then started thinking.. I almost always mix two gallons. I grabbed the Echo brand and seen the big "2" and assumed it was for 2 gallons... of COURSE I didn't have on my glasses to actually READ the bottle before hand... So, my meticulous blend was 2 gallons of gas to 2.6 oz. of oil for a ratio of 100:1 not the 50:1 needed!!!! SUNOFA%$#@!!
After getting over smokin' the saw.. well.. not really over it... I started thinking that this wasn't the first fuel tank I used that with, so, I ran over two gallons of 100:1 fuel in the Stihl and Echo.. and only smoked the Stihl. It sees heavier use... I ran the Echo for two trees while I was waiting to hear the diagnosis on the Stihl... So I could have EASILY smoked the echo as well..YIKES!!! Maybe running the Stihl synthetic mix before, helped this long??? SO, in the end. I was RIGHT! I did NOT run straight gas!!!... YEAH for me!... however.. I ran t with only half the oil mix it needed.. what a dufus!!!
So, On the Stihl site, I updated my review and ended it with an apology to Stihl.. it was a great saw.. until that happened... If I rebuild, I want to find out if I can update with a larger cylinder and piston.. I've read where a person updated their MS290 toa MS 390.. wonder if I can do similar.