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Stihl 362 C-M scored piston

Discussion in 'Chainsaws' started by Travis-Mc, Nov 8, 2018.

  1. Travis-Mc

    Travis-Mc New OPE Member

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    Hey guys I'm new here... I posted on another site about this same issue, but thought I post here too.

    The piston in my Stihl 362 C-M looked great last week. I know this because I took pictures when I was asking about if the compression of 135-140psi is okay for this saw with about 3 gallons of gas through it.

    Well now I have a real problem. I was out cutting on Saturday and after maybe 10 minutes the saw starting having problems idling, and then wouldn't start. I figured the solenoid crapped out since I've been told they can be a problem. I grabbed my little husvarna 345 and after several minutes it started having problems running too. I dumped all the gas in both saws, mixed up some fresh stuff and both saws worked fine after that.

    So today I pull the muffler cover off the 362 and the piston is scored. Ugh! I know the gas has oil in it as I've been using it for a while (weeks) without any problems. Premium 91 octane gas with no ethanol, and Stihl Ultra oil mixed at 50:1. It was probably 2 months old.

    What the heck! Both saws have the same compression as before. The 362 is at about 135-140psi. I've attached pictures of the 362 piston. Think I should keep running it since the compression hasn't changed?

    Top
    top.jpg

    Middle
    middle.jpg

    Bottom
    bottom.jpg

    That deeper scratch on the left side in the middle has me a little worried.
     
  2. Armbru84

    Armbru84 Pinnacle OPE Member

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    Definitely don’t keep running it...it’s gotta get pulled down and it’s going to need some top end work.
     
  3. CR888

    CR888 Pinnacle OPE Member

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    I'd wanna pull the jug to inspect it for piston transfer and clean it up. Buy a new piston/rings and install it. Many consider 2 month old gas fresh......I don't.
     
    andyshine77 likes this.
  4. Travis-Mc

    Travis-Mc New OPE Member

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    Thanks for the replies!

    Alright, time to take it apart then. Hopefully the cylinder is okay. I have always tried to keep my mix 2 months or less, and usually dump it when one machine or anther isn't acting quite right. The only thing I can think of that is different this time is the gas station I went to doesn't get a lot of traffic, so maybe the premium gas in their storage tank was already old.

    I was already considering porting the saw. Maybe now is the time to remove the base gasket or use a thinner one (my squish is at .031") and do a mild port job on it. I have a lot more reading to do before tackling that though.
     
    andyshine77 likes this.
  5. andyshine77

    andyshine77 Super OPE Member

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    Fuel can go south quick, especially in the heat. I have to also say, from the pics you provided, things look quite dry, like no oil dry. It is entirely possible to run a saw quite awhile with no oil in the fuel, not saying that's definitely what happened, but everything sure looks like it lacked oil. Now because you ran the saw on fresh mix it will be hard to tell if you made that mistake or not, brain farts do happen all the time lol.
     
    smokey7 likes this.
  6. Travis-Mc

    Travis-Mc New OPE Member

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    If I straight gassed them, that would mean I've been straight gassing 3 saws and my brush cutter for the last several weeks. Both saws started acting up within 10 minutes of each other, so I have to blame the gas, and not the saw. But the gas seemed fine a week before when I bucked up some oak for about 25 minutes.

    If the mix sits for a while and you don't shake it before pouring it, will the oil settle? I usually swirl the gas a bit before adding it to the saw, but maybe I didn't last time. Plus when I gassed them up the day everything went to hell, both saws were already half full from the last time I used them.
     
  7. Chainsaw Jim

    Chainsaw Jim #fartedinthebandwagon

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    It sounds like it's time for a complete servicing with new fuel line/filter, tank filter, crank seals, carb kit/boot.
    The piston doesn't quite appear out of spec yet and can be cleaned up for reuse, but the rings may need replaced.
     
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