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Stihl 064 gas tank breather?

Post in 'The Gear' started by Joful, Feb 10, 2013.

  1. Joful

    Joful Minister of Fire

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    So, I've had a problem with my 064 AV the last few times out. Runs great for five or ten minutes, then starts to die. Keeps stalling out between cuts, and eventually gets to a point where I can't restart it. No decompression valve on this monster, so restarting a dozen times over is not a minor detail, either.

    Suspecting it might be a fuel pick-up issue, I noticed it was always happening when I had used maybe 1/2 the tank of gas. I had it in my head it must be a crack in the fuel pick-up hose, but then today noticed the tank makes a hiss sound when I unscrew the lid. So, when it stalled today, I simply loosened the lid and retightened, and voila! She ran fine again.

    Seems I have a problem with pulling a vacuum on the tank, and no make-up air can get in. Who knows where they hide the breather on these tanks? I'm assuming a sintered bronze, like they used on older saws, or has the technology changed?

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  2. MasterMech

    MasterMech Guest

  3. Joful

    Joful Minister of Fire

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    Hmm... reading that, I see it's not abnormal to have positive pressure in the tank. Maybe the hiss I hear when I remove the gas cap is pressure, not vacuum! Might have to experiment more with this saw, but I do worry about it running lean at WOT, if the tank isn't venting right.
  4. I'd say your first thought about the fuel line could be the problem. My 029 acted the same when the fuel line had a hole in it.
  5. MasterMech

    MasterMech Guest

    If the saw runs fine after you crack the cap, then you definitely have vacuum issues in the tank.
  6. Joful

    Joful Minister of Fire

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    Yep... exactly what I was implying. Any concern with it running lean, though? I'd like to run it another day, cracking the cap to see if it fixes the problem after each stall, just to verify this is the problem.
  7. MasterMech

    MasterMech Guest

    Running again to verify the problem probably won't hurt it.

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