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2stroke Hedge trimmer: got spark, replaced carb, no start

Discussion in 'Tools and Materials' started by Cvdabbeele, 21 Dec 2020.

  1. Cvdabbeele

    Cvdabbeele

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    Hi,
    Would anyone have any tips on what might be the cause of the following problem?
    Any tips are appreciated

    I have a McCulloch SuperLite 4528 (aka McCulloch Ergolite 6028) 2stroke hedge trimmer
    - It has a spark
    - When I spray fuel in the carburetor, it starts fine (then it dies. Sometimes, with a lot of trouble and luck, I can keep it running; mainly by playing with the choke)
    - I have installed a new carburetor but problem persists
    - I can blow in the fuel line (back to the tank): fuel filter seems not blocked
    - fuel lines seems not pinched
    - when I push the primer bulb, I see fuel going into the carburetor and coming back to the tank through the return line

    What am I missing?
    thanks so much
    (my first post here)
    Chris
     
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  3. Bilabong007

    Bilabong007

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    When you lift it by the pullcord, does it just drop to the floor or will the pullcord hold its weight? Does it have much resistance to it being pulled?

    I would try and test compression if you can, could be piston rings/oil seals.

    I had a mculloch that had been dropped and cracked the crankcase at the coil so it would bounce along the flywheel

    Sounds like you have yourself a project

    Graeme
     
  4. Burnerman

    Burnerman

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    When you say its a new carb Chris, is that brand new or a second hand one? Was the fault the same with both carbs?
    Either way, if there are any adjustment screws on the side of the carb, maybe marked L and H, turn them fully in, and then out again one and a quarter turns.
    Another possibility.....thoroughly check the fuel pipes from the tank. They often fracture where they pass into the tank and that fracture is hard to see. The pipes may pass through a rubber grommet or may just push through the plastic.
    John :)
     
  5. Cvdabbeele

    Cvdabbeele

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    thank you Graeme and John, for your fast response and great tips

    @Bilabong007
    I do feel a resistance when pulling the starter cord. If it is enough, I can't tell.
    I am tempted to buy a compression tester at AliExpress. Any thoughts on that? are those Chinese testers any good?

    @Burnerman
    The Carb is brand new indeed (see: https://www.aliexpress.com/wholesal..._20201222003828&origin=y&SearchText=523012401 )
    I am a bit reluctant to start tuning it, as this often means that you are compensating for an issue (in stead of solving the issue)
    I will order new fuel lines, a new fuel filter and a new carburetor gasket.
    I am suspecting that the engine either pulls in air with the fuel, or it is not getting enough fuel
    I am figuring out the diameter of the fuel lines; I guess I'll order a set of different diameters

    thanks again,
    chrisV
     
  6. Burnerman

    Burnerman

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    I wouldn't worry too much about buying a compression tester - these tiny two strokes don't have a lot to show when you crank them over.
    If your thumb gets blown off the spark plug hole when you crank the thing over, that's a good sign.
    Another tip - if you remove the exhaust silencer and peer in, you'll see the piston and rings....there shouldn't be any severe scratching or signs of the rings being stuck in their grooves.
    Be amazed at the variety of fuel pipe on offer - it's ridiculous. Over here, GHS Ltd supply what's needed.
    John :)
     
  7. Cvdabbeele

    Cvdabbeele

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    @Burnerman
    Those are great tips John
    I had already looked at the piston and rings after removing the carburetor. I'll take another look via the exhaust
    thanks again,
    chrisV
     
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  9. Burnerman

    Burnerman

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    Good luck with it Chris!
    I’ve had two incidences this year where the cylinder barrel has departed company from the crankcase, courtesy of a snapped off screw......these machines were both Ryobi where there are two screws on one side and one on the other.
    Happy Christmas
    John :)
     
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  10. mrrusty

    mrrusty

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  11. Cvdabbeele

    Cvdabbeele

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    @Burnerman , @Bilabong007
    I wanted to close the loop on this and thank you both again for your recommendations

    My McCulloch SuperLite 4528 now runs like a breeze

    There was an air leak between the cylinder and the main part of the engine

    It turned out that the 2 screws that attach the cylinder to the motor were rather loose. (yes the cylinder is attached to motor by only 2 screws)
    Luckily, because of all my fiddling, this got worse and worse until I noticed that the cylinder actually moved a bit versus the rest of the engine when I pulled it
    I tightened them and... happy days !

    As a bit of background, I just need to mention that this was an old, broken, hedge trimmer that I got pretty cheap, so I had no (service) "history" of this thing
    This may not have been the root cause why this hedge trimmer was put out of service. It looks more like it that as a "last" resort someone opened the engine and loosely put it back together again. Anyways... this thing starts and runs like a breeze now
    cheers,
    chrisV
     
  12. Burnerman

    Burnerman

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    That’s exactly as per my post #7 Chris.....unbelievable! It’s the last place you’d normally look for faults.
    Anyway, success came your way so well done!
    John :)
     
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  13. Cvdabbeele

    Cvdabbeele

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    @Burnerman
    ah, right..."the cylinder barrel has departed company from the crankcase" I now understand what you meant
    I must admit that I had not really understood it back then (being a non-native English speaker)
    But now it makes sense. You actually predicted it ! :)
    thanks again
    chrisV
     
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  14. Burnerman

    Burnerman

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    Hell Chris you speak English better than me :ROFLMAO:
    Wonderful country, Belgium.....I’ve been to Dixmude, Bruges and Ieper many times - absolutely wonderful.
    John :)
     
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