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Straight gas in a 2 stroke engine?

Discussion in 'The Okie Corral' started by fireguy129, Mar 28, 2010.

  1. fireguy129

    fireguy129

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    Pulled a real bonehead move and ran about half a tank of straight gas through my Stihl saw. I thought when I was pouring it that it looked light, finished cutting and loaded up. Got home and found my saw gas, marked MIX in big black letters, sitting right next to where I store my saw. Think I did any damage? Should be the only time I ran straight gas in it, and I definitely plan on draining the gas asap.
     
  2. G30SF/F-250

    G30SF/F-250 Pinky Out Platinum Member

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    I am suprised it ran that long.
     

  3. zeke66

    zeke66

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    Nothing you can do now. Just drain, refill with gas/oil mix and see how she does.
     
  4. 88_gurgel

    88_gurgel

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    Ouch,

    I would bet you have a rebuild in your future. Scored cylinder walls, scorched bearings, and the like.


    Maybe buy some marine fogging oil, put fresh mixed gas in the tank, start it and spray the fogging oil through the carb. It should help re-coat the cylinder walls and bearings.
     
    Last edited: Mar 28, 2010
  5. Rinspeed

    Rinspeed JAFO

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    That's too bad, the chances of there not being damage are slim to none.
     
  6. Flying-Dutchman

    Flying-Dutchman

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    All you can do now is keep running it although you put some heavy wear on it.

    The modern 2 cycle oils are so good you can get away with a 50:1 mix instead of the old 32:1 or 16:1.

    Maybe there was enough residual oil/gas mix in it to give you some protection.
     
  7. FullClip

    FullClip NRA Benefactor CLM

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    Like Zeke said...it's too late now, any damage is already done. I'd just drain the raw gas, fill it up with the regular mix and see what happens. Stihls are a good saw, and maybe it will be OK.
    My nephew did the same thing to my ice auger a few years ago, but the thing still works without any syptoms of engine problems.
     
  8. 88_gurgel

    88_gurgel

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  9. Ol Timer

    Ol Timer ↓ hog hunter ↓ Millennium Member

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    Hopefully you had enough premix in the tank when mixed with the straight gas it still had some lube properties.

    She probably needed a good scrubbing anyhow.
     
  10. fireguy129

    fireguy129

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    Beautiful. I guess no good deed goes unpunished. I'll drain it out and see how it runs. I was going to have it tuned anyway, I guess I'll just have the shop check it out. Thanks guys.
     
  11. NailShooter

    NailShooter

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    If you're worried, remove the muffler and look thru the exhaust port at the condition of the piston skirt. If you hurt the saw, the exhaust port side of the piston often begins to scuff first. Like Ol Timer said, there may have been enough oil in the tank from the previous fill to prevent damage. I'd do this before/instead of taking it to a dealer.

    There's not much "tune up" work to do on a modern saw w/ electronic ignition. Screw in a new plug, install a new air filter, sharpen or put on a new chain yourself or pay the dealer 80 bux an hour to do the same.

    If the saw runs normally and still starts OK with a fresh fill of pre-mix then you likely didn't hurt it.

    Nail
     
  12. tlafrance

    tlafrance Missing AZ

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    Bet it ran like a raped ape! Drain, refill with correct mix, carry on. Loose no sleep. About a million years ago I had a Yamaha DT175 2 stroke enduro bike. One spring day while riding around I thought "WOW, this thing is running great today". About that time, BOOM and the rear wheel locked up. Upon trying to restart, no compression. The oil injector had failed and caused a burned hole in the top of the piston, just like a blowtorch. After a new piston, rings, etc (less than 100 bux) and a few hrs work, I was back in action. From that point on, I always used premix. Running 2 strokes lean, causes wear but DANG they run good (until they blow up:rofl:)

    Tom
     
  13. fireguy129

    fireguy129

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    Actually, it wasn't running that well all day. Started fine, but low idle and stalling. Didn't seem to really be running wide open all day, but I don't use it much and attributed it to ethanol in the fuel. That crap plays hell on our small engines at the fire station. Maybe it is running ok, and im just used to the Cutters Edge saws we run. Now those run like a raped ape!!
     
  14. mrbray101

    mrbray101

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    I let someone borrow my echo SRM260 string trimmer one time. They brought it back to me with a piston melted to the block from using straight gas.

    You may want to go ahead and rebuild it but not much else you can do now. Maybe you had enough fuel in there to dilute it some. Good luck to you, Stihl saws are hard to beat.
     
  15. Diesel_Bomber

    Diesel_Bomber

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    This.

    I think Stihl recommends 50:1 now. If you do like I do and run 32:1 of a good synthetic, then half a tank of straight gas on top of a tank of mix will drop you to 64:1..........still protected. Like others said, I'd yank the muffler and have a look-see. Price a P&C if you think the damage warrants it.
     
  16. jmiley

    jmiley

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    If you had some premix in the tank already and the residual oil in the motor that is probably what saved it.

    Could the fuel you used have had some oil in it that just got diluted?

    If you didn't blow it up already, you are probably OK.
     
  17. stopatrain

    stopatrain Lifetime Member

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    My brother ran mine with no oil, when he returned it to me it was brand new. So it worked out ok.
     
  18. 88_gurgel

    88_gurgel

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    That ethanol crap really messes things up. I hear 100 low lead works well and smells great for small engines but never tried it out. I think it is about $5 a gallon.
     
  19. bobby_w

    bobby_w Alienigena Platinum Member

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    This also shows the quality of Stihl and tolerences built into a good tool.

    I use nothing but Stihl gas powered tools and have not regreted the cost.
     
  20. Diesel_Bomber

    Diesel_Bomber

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    100LL is a slow burn fuel and doesn't do well in high-rpm engines.

    My chainsaws lose top-end power on 100LL.