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Analysis: MS 271 w/ Torched p&c, bearings, connecting rod [PICS]

Discussion in 'Chainsaw' started by Sam R, Feb 7, 2019.

  1. Sam R

    Sam R 8mm Socket

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    Good morning folks,

    Pictured is the guts from a smoked MS 271 that came in to the shop with a complaint of non-running.
    Externally there was not much of note; except see the chain in the pictures. Every cutter tooth looked like the ones pictured. I'd never seen this before but I was told it's the result of running a dull chain so long that it actually begins to bevel the top of the cutter tooth.

    Based on findings inside the cylinder & crankcase, I believe this saw was ran at excessive unloaded RPMs for an extended period of time as evidenced by the destroyed main bearings, bluing on the connecting rod and transfer/detonation on the exhaust side of the piston. There's a small amount of melt over the clutch side bearing and the clutch itself was almost completely blue.

    Finally there's some build up in the crank pan which appears to either be material from the bearings & piston or it could possibly be where the oil broke down in the extreme heat. I believe the series of events leading to the total failure of the unit went something like: Excessive RPM > lubrication breakdown > bearing failure (followed closely by seal failure on clutch side) > swelling of piston in cylinder due to RPMs and lean condition > detonation from heat > loss of compression > total failure.

    20190206_101453.jpg 20190206_101510.jpg 20190206_101539.jpg 20190206_101550.jpg 20190206_101617.jpg 20190206_101719.jpg 20190206_101740.jpg 20190206_101349.jpg 20190206_101418.jpg 20190206_101442.jpg
     
  2. Stonesforbrains

    Stonesforbrains ArboristSite Member

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    Looks like a survey crews brush saw for cutting line. That’s an expensive saw for that though.
     
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  3. Sam R

    Sam R 8mm Socket

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    It was homeowner bought and owned. Farm saw I think they suggested going up in size. Don't know if that would help since excessive RPM is what killed this particular saw.
     
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  4. HarleyT

    HarleyT Tree Freak

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    Take off the oil pimp and lift the crank out.
     
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  5. HarleyT

    HarleyT Tree Freak

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    He is the one with the long feather in his hat..


    Sorry, I meant oil pump.
     
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  6. grizz55chev

    grizz55chev Tree Freak

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    Rest in pieces, poor little saw! That chain tells a story, get that man a cheap Poulan!
     
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  7. TheBrushSlasher

    TheBrushSlasher I have chainsaws and chainsaw accessories.

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    Someone was forcing the hell out of that thing to make it cut with that chain. They hit the rocky dirt with that thing and forcing it to cut caused it to get real hot.
     
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  8. Sam R

    Sam R 8mm Socket

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    What's your purpose in doing that, Harley?
     
  9. Sam R

    Sam R 8mm Socket

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    That was my estimate as well. Of course the customer said everything was operating normally and it just **** a brick all out of the blue. The chain knows what you did...
     
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  10. HarleyT

    HarleyT Tree Freak

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    Well, if you are going to work on the saw, you should lift the crankshaft out.
    Also see if the oil pump is damaged if you are working up an estimate.
     
  11. Sam R

    Sam R 8mm Socket

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    Good point on the oil pump. Estimate so far at P&C, bearings and seals + labor was over MSRP for a new one. Our Stihl vendor sold them a new one at a discount but wouldn't warranty the saw(thank heavens).
    As it is, it'll probably take up residence in the shop as a parts saw.
     
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  12. grizz55chev

    grizz55chev Tree Freak

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    OEM prices are up there,
    Sell now- Have one to sell?
    OEM PISTON / CYLINDER / CRANK STIHL MS271 MS291 CHAINSAW GENUINE STIHL

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  13. Sam R

    Sam R 8mm Socket

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    Customer gets a new one, I can't use outside parts OEM or otherwise so it's a moot point now.
    But that would be a good resource for someone not wanting to pay $400 for a new* 271
     
  14. LegDeLimber

    LegDeLimber Addicted to ArboristSite

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    What does the fuel in the carb look like?
    It may just be my eyes getting old, but...
    Other than some residue in the bottom recesses, I can't seem to see any oil film on the (moving) guts.
    Any chance the saw got a short dose on the oil mix?

    I could see screaming the saw with that dull chain and raw gas, melting 'er down before it had a chance to flush the corners of the cases and behind the bearings.
     
  15. Sam R

    Sam R 8mm Socket

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    They were using Motomix in the saw, that's what they told me and was consistent with what came out of the tank.

    The residue in the bottom is what concerned me, that could be from the trashed bearings or transfer but there's definitely some "stuff" down there - especially given it's practically a brand new saw.
     
  16. HarleyT

    HarleyT Tree Freak

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    Wait!!!!!

    It's under warranty????!!!!!

    Stihl won't stand behind their products????!!!!
     
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  17. grizz55chev

    grizz55chev Tree Freak

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    Hmmmm! o_O
     
  18. HarleyT

    HarleyT Tree Freak

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    Lowes would have replaced my Husqvarna!!!
     
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  19. Sam R

    Sam R 8mm Socket

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    Bryan equipment at least said no. And I agreed with them, but they did give the customer a discount on a new one.
     
  20. HarleyT

    HarleyT Tree Freak

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    If the guy would raise enough hell, he would get it covered.
     

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