Chainsaw with scored piston. How?

Buxus · Dec 4, 2018

2013 Stihl MS 362 with 18 inch bar; Cutting a holly stump about 16 inches, did not pinch. Saw died. Brought to dealer and was told it was scored piston. Initially dealer said it must be bad gas, which it isn't. Then he said must have overheated. $500 repair on a $725 saw. I'm pissed as ****, but don't know what to do.

Saw doesn't see a ton of work because I mostly use my smaller saw as I do mostly branch clean up on my property. Don't heat with wood. The big saw is for the occasional big tree down. So the saw is not beat up at all. Doesn't get used a lot, but when I need it, I need it.

Always used premixed gas in a can, chain always oiled and sharpened. Gets about q2 yr service at dealer, but only sees a few hours of work a year. Not only don't I lean into it when cutting, but I probably can't as I weigh 135 lbs. The dealer said cutting smaller trees with it than the blade is long (in other words not having the blade buried) allows it to spin too fast and overheat. Is this true?

Thoughts? I'm unsure about buying another/getting fixed when I don't know what I did wrong in the first place.

mcfarmall · Dec 4, 2018

If the "cutting smaller trees than the bar length" was true, then Stihl would be making saws with 6" bars. I call BS on the dealer. Unfortunately the cost of repairs is >50% the cost of a new saw, so with that train of thought, I'd keep it for parts and buy a new one.

I mix my own fuel with ethanol free "rec gas" and run 40:1 and never had any problems.

Diggin It · Dec 4, 2018

It really doesn't take much to do that I don't think. I had one seize up on me ( a cheap Homelite). I'm guessing I overheated it. I was able to get it freed up and run it for quite a while before it died for good.

Don't really know what happened to yours. But this is why I don't buy high dollar items. When they fail, they cost more to fix. My first two were Homelite rebuilts I got for under $100 and when they died, I didn't worry about fixing them. The second one I was also able to bring back for little money however and am still using it to an extent. Most recent is a Blue Max with two bars and chains for $150 or so.

Have you looked into parts to try and fix it yourself? You may be able to get a short block, piston and ring kit from a third party supplier.

BigBlue1 · Dec 4, 2018

If you're handy with mechanical things perhaps consider rebuilding it yourself. I rebuilt a McCulloch Pro Mac 800 that had a chunk of something go through the cylinder. Piston was shot with a major gash in it that chewed through the rings too. Cylinder had some scratches. I had a local cylinder head place polish the scratches out (didn't take much - I think they might have been more from aluminum transfer than actual scratches) and I bought and installed a new piston. If one can do that with a 25+ year old Mac I'm sure the parts are available for a modern Stihl. Chainsaws aren't that complicated... just lots of parts. There are probably good forums online with Stihl gurus that can give you tips on disassembly & reassembly. You'll save a ton of $$ this way.

Rob

ruffdog · Dec 4, 2018

What could of happened:

Maybe there was a vacuum leak that allowed the saw to run lean and hot. This can happen on new or old saws. Is/was a pressure/vacuum test done on the saw to find the cause and to prevent it from happening again?

For 2-strokes, the big danger with running ethanol E10 fuel is what happens after the fuel absorbs water. As the ethanol absorbs water, there is a point that the gas/h2o/ethanol mix will want to separate from the 2-cycle oil. If this happens, at some point the engine will be operating without oil in the fuel mix.

Being that the saw has a few years on it, most times the carburetor diaphragms can get stiff and not pump enough fuel, especially when worked.

Maybe a cracked fuel line allowing air to lean the air/fuel mix.

Was the air filter doing it's job by not allowing dirt past it?

EddieWalker · Dec 4, 2018

I had this happen to a Husqvarna that was less then two years old and probably had about 20 hours on it. Dealer said that it would cost more to fix then it was worth, so I decided to buy cheap saws since they didn't last very long. Cheap saws where too cheap and a total waste of time. I was taking them back after just one day of trying to get them to run, and stay running. Then I decided that Husqvarna was a cheap saw and that I had gone in the wrong direction in my thinking and bought my first Stihl. I have several of them now, but then discovered Echo, which I like even better!!!

ArlyA · Dec 4, 2018

Buxus, Sorry to hear of your grief. I can't tell you what happen to your Stihl but I do think they are a quality built machine, but I can tell you what happen to an Echo* we have. It was about a year old and we were in the fielding doing trail work. We stopped for a break and after that, it wouldn't run worth a hoot. It wouldn't spool or rev up which was strange, since it ran perfectly just 15 minutes earlier. We took it back to the dealer who tested it and called Echo who suggested doing this and that to find out what happened. They eventually figured out the cylinder was scorn and they gave us a new unit since it was a year + old. Point is, they didn't know and couldn't figure out what happened, but that's an answer we can sometimes get. It can happen....

* We have several Echo's and use them for many, many hours each year.

bigsilver · Dec 4, 2018

Replacing the jug and piston on a pro series chainsaw is not a very difficult job. A quick search and a jug and piston is <$100. Plenty of write ups and videos on the subject if you don't know where to start. It's up to you, but I would at least watch a video before making a decision to have the dealer work on it or buying a new saw. I agree with ruffdog about the saw leaning out is probably the reason the piston was scored in the first place.

adventure bob · Dec 4, 2018

Couple of questions: is it still under warranty? How many hours on it? If its still under warranty, ask the dealer to provide the results of the leak test before he tore it down. If he did not leak check it then you have a viable claim with Stihl. He has to prove something you did was the cause of the scored piston before he can deny your warranty claim. If he says it was bad gas, ask him how he knows that. If he did not have the gas tested that cannot be used as a denial basis. "it looks bad" wont hold up. I have a husky that I went round and round with the dealership and finally the husky rep acknowledged that the dealership didnt do due diligence before denying my claim. Mine turned out to be an air leak in the transfer cover gasket. However the dealerships first answer was bad gas. I said prove it. We have this thing called the Magnuson act which governs consumer protections under warranty.