Stihl Chainsaw Rebuild

Discussion in 'Mechanic and Repair' started by FuzzyOne, Sep 9, 2004.

  1. FuzzyOne

    FuzzyOne LawnSite Member
    from NJ
    Messages: 81

    I bought a MS 360 2 years ago and ran maybe 3 gallons of gas through it. The other day when cutting firewood, it got real hot but didn't "officially" seize. Well, after letting it cool, I couldn't start it.

    Took it back to the dealer and he said the piston and cylinder were pretty scored and the compression was low. He said to scrap it due to the cost of a rebuild. He also said I must not have mixed the gas right. That's BS and I only ran Stihl 50:1 oil.

    Anyway, I'm looking around and find rebuild kits for $150-$200. Is this a do it yourself project? Would I need any special tools? I'd really hate to lay out another $360 for a chainsaw. BTW, the dealer gave me a price of $350 to do it.

    Thanks for the help.....
  2. txlawnking

    txlawnking LawnSite Bronze Member
    Messages: 1,905

    Fuzzy, on a saw that inexpensive, I would side with the dealer.. Just imagine this..Anytime the repair cost exceeds 70% of the device's value, you're usually better off to replace rather than repair.. Kinda like rebuilding the entire drivtrain on a wrecked, rusted junk car..Some folks insist on doing it, but It doesn't make sense.. To answer your question though, If you replaced the crank assmbly, and the top end too, You probly wouldn't need any "exotic" tools, but if you've never done this before, you may want to heed the dealer's and my advice...Not trying to upset, I just don't want to see you make a bad deal..
  3. vipermanz

    vipermanz LawnSite Bronze Member
    Messages: 1,773

    You have to have patience and keep your "operation" surgical clean, use a small engine honing tool to VERY lighty smooth the cylinder walls, Lube every internal part when reinstalling
  4. kkat

    kkat LawnSite Member
    Messages: 62

    If you have never done anything like a rebuild before it could be quite a job also take a look at the cylinder if it is scoured like the dealer, said there are only 2 reasons it would be like that-it was either sucking in dirt or the gas oil mix wasent correct, so somewhere along the line somebody goofed. These ( motors run extremly lean (50/1 mix) now care has to be taken when mixing the gas and oil, if the mix had been sitting for a while the oil would have setteld and most likely you put straight gas into the saw , shake the mix up before you use it if it had been sitting for a while.
  5. FuzzyOne

    FuzzyOne LawnSite Member
    from NJ
    Messages: 81

    Thanks for the replies. I think I'll just buy another one (same model) and keep this one for parts.

    I know the gas/oil mix was correct. Hell, I still have 2 cycle stuff that is 10 years old and still starts on the second pull.

    One thing that probably is my fault is that I ran it hard right out of the box. I didn't allow for any "break-in" as the manual suggests. My next one I'm going to run 40:1 and baby it for awhile.

    Thanks again.....
  6. hosejockey2002

    hosejockey2002 LawnSite Bronze Member
    Messages: 1,195

    I don't think you will do your new saw any favors by running 40:1. From talking to a Stihl rep, you won't get better lubrication, you'll just foul the plug and gum up the carb. Use Stihl or other name brand 2 cycle oil, mix it 50:1 and keep it fresh. He also said it's critical to service the air filter often, about every 8-10 hours. According to him, a lot of guys will run saws with the air filters all plugged up, and then wonder why they run rich. So they adjust the carb to lean it out (another no-no), eventually replace the filter which leans it out more and then they wonder why they burn their saw up.
  7. saw man

    saw man LawnSite Bronze Member
    from utah
    Messages: 1,033

    By looking at the cylinder and piston you can tell what went wrong! No oil, dirt, rpm.
    Make sure your rpm is set correctly. I would do the same thing and get the same saw, and use the other for parts.
  8. FuzzyOne

    FuzzyOne LawnSite Member
    from NJ
    Messages: 81

    Thanks again for the replies. I bit the bullet and bought another one today. :cry: It turns out this model was pretty hard to find. I had to check 4 Stihl dealers. They said most of the stock has been shipped to the south due to the hurricanes. I'm going to baby it for the first few tank fulls. The more people I talked to, the more that said to just get another one.

    It just kills me because I know I mixed the gas right.

    So much for saving money doing my own firewood. I may have to sell some to recoup my loss.
  9. landcruiser

    landcruiser LawnSite Member
    from Tx
    Messages: 134

    I work on saws often. I am not sure on your particular model, but every saw I've worked on has adjustable low and high side jets. The #1 cause of failure on most saws is running the high side jet to lean. Do not confuse this with improper or lean fuel/oil mixture. They are 2 totally different things. Mix your fuel/oil mixture at 50:1 as Stihl says. Use clean, fresh fuel and quality oil. Beyond that, the fuel/oil issue has nothing to do with it. Your saw will get enough lubrication at 50:1 - no question about it. But, if your saw was running too lean at high rpm's due to the high side mixture screw being screwed in too far, it will seize rings and/or gauld a cylinder wall in a hurry. You should hear a "grunting" sound periodically at 3/4 to wide open throttle when running a 2 stroke. Many mechanics refer to this sound as "4-stroking". It is a good thing to hear. This is indicative that it is running rich enough at high rpms and will prevent overheating and ring seizure/piston scoring or melting. It is easy to find this sweet spot at which your 2 stroke is most happy. Once your saw is up to temperature it is best to adjust the high side screw at wide open throttle. Be careful as it takes just a minute adjustment of the screw either way to make all the difference in the world. At wide open throttle, turn the high side screw in (clockwise) until there is a noticeable decline in rpms - note where the position of the screw is. Now, gradually, turn the high side screw out until your hear a noticeable "grunting" or "4-stroking" sound. Note that, again, there will be a decrease in rpms because with the screw too far out the saw is running too rich and drowning in fuel. Now you have your window in which to tune the saw. It will more than likely be 3/4 of a turn or less from each of the 2 positions you just saw. That is, the point at which you screwed the high side screw in a got a noticeable decrease in rpm's vs. the point at which you screwed it out and got another decrease in rpms and the obviouse "grunting" sound will more than likely be withing 3/4 of a turn from each other. Now, in general, it is best to put the high side screw half way between the two points. Now, go stick the saw in some wood and listen to it carefully. When it hot out and you are running it hard, listen for that grunting sound under load. If you don't hear it at all, turn the high side screw out just a bit. If your hear too much grunt, you are a tad rich so screw it in just a bit. Do this very deliberately until you are confident you have it just right. Always keep in mind that a saw running too rich on the high side will never hurt it but if it's too lean you run the risk of damaging the piston and rings as well as the cylinder. There is a VERY fine line between a "happy" saw and a "soon to destruct, I am running too lean" saw. Your ear listening for that "grunt" and taking time to tune for it makes all the difference.
  10. Joe B J

    Joe B J LawnSite Member
    from Alabama
    Messages: 37

    agree with that 100%...when adjusted as you describe the saw may not turn as many rpm's, but will have more 'power' at the high rpm's.

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