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Thread: 088 hydrolocking

  1. #11
    TreeHouser Magnus's Avatar
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    Water in fuel can cause hydro lock, a significant amount of fuel as well..
    There is no partial hydrolock..
    If there is anything above piston that can cause hydro lock it can get out thru exoust port or down in crank case.
    A pull or two with plug out will let you know (kill switch activated) if you can't see anything on plug or on piston.

    Have you checked for carbon buildup in exoust port and piston top?

    Opening fuel cap to ease start has quite the opposite affect as you release the pressure needed to help fuel pump.

  2. #12
    TreeHouser Nutball's Avatar
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    Opening the cap on they way to the job prevents pressure from forcing gas through the carb (probably due to a carb with imperfect seals)

    Too much carbon buildup in the cylinder may have increased compression way too much.

    Hydro lock would probably not feel like kick back, but just plain locking. 2 strokes tend to empty the cylinder of a hydro lock condition easily until enough rpm is reached to force pooled liquid from the crank case into the cylinder, such rpm is reached while cranking or just after the engine starts firing.

  3. #13
    TreeHouser Sponsor Raj's Avatar
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    Good info!

    2nd day. Put the saw to run, a bunch of pulls, then choke and start normally. No kick back or piston stop.
    Peter

  4. #14
    TreeHouser Nutball's Avatar
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    I'm going to guess the kick back comes from a flooded rich mixture.

    1) Piston goes up, fuel ignites and burns very slow as the piston goes down
    2) exhaust port and transfer ports open adding more fuel and air, AND disturbing the flame front causing a faster burn
    3) Piston goes back up, closes ports, and tries to compress an already burning mixture.

    That's one theory, but I'm certain I have felt kick back on the first stroke from a few engines almost like an explosively lean mixture (which contradicts other conditions involved), or early spark which seems impossible.

  5. #15
    TreeHouser Sponsor Raj's Avatar
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    Good info.

    In my case there has been no noticeable exhaust or burnt fuel indication.
    Peter

  6. #16
    TreeHouser Magnus's Avatar
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    Quote Originally Posted by Nutball View Post
    Opening the cap on they way to the job prevents pressure from forcing gas through the carb (probably due to a carb with imperfect seals)
    The main inlet valve is what hold pressure as well and most tank vents regulate pressure unless they are one way valved.
    Even if it shakes ever so much it will not build more pressure than needed or else every saw riding on a machine would explode!
    Quote Originally Posted by Nutball View Post
    Hydro lock would probably not feel like kick back, but just plain locking. 2 strokes tend to empty the cylinder of a hydro lock condition easily until enough rpm is reached to force pooled liquid from the crank case into the cylinder, such rpm is reached while cranking or just after the engine starts firing.
    Hydro lock feel like you put a M10 nut in cylinder. There is no way around it and it doesn't go away unless the fluid escape to case or muffler. no need for rpm, just back a bit so ports open and down it go...
    Rods have bent and busted from hydrolocking...

  7. #17
    Treehouser Frankie's Avatar
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    Click image for larger version. 

Name:	D4B089E3-7C4A-4D6B-A465-00D5B9F427E5.jpeg 
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ID:	95124 not conducive to performance lol ... hard to fathom a chainsaw hydro locking as per definition ... a vehicle crossing a stream under hard throttle yes !

  8. #18
    TreeHouser Magnus's Avatar
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    Its rare.. I have seen it a couple times on 15 years repairing and looking at the saws I got. One time from water, one time from oil.
    It is needed quite a bit to get enough to fill compressed volume above piston. A squirt from crankcase won't do it and it needs to be running so there is momentum and forces. I doubt you bend rod with puller...

    I do get to see a lot of odd stuff. I bought up lots from dealers between 2 saws and 40 cubic meters of saws and parts. Parted out well over 1500 saws now and got 800 in collection, 4-500 or so doubles and "to be parts"..
    + costumer saws...
    So I see a bit of odd stuff...

  9. #19
    Treehouser Frankie's Avatar
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    Magnus , 800 saws ? !!! That’s quite the collection

  10. #20
    TreeHouse Administrator MasterBlaster's Avatar
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    Magman has a SHITLOAD of saws!