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  1. #1

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    Craftsman 2 stroke 25cc string trimmer only runs on 80% choke

    Hello! I am working on a string trimmer for my neighbors, which is a craftsman branded 2 stroke. Seems to be pretty new. When he gave it to me, he said it would start but promptly die. It did that. I changed the fuel out of it, took the carburetor sides off (both the metering and fuel intake diaphragms looked ok, felt silky), and nothing looked too dirty. Cleaned it up with some water, reassembled it and still doesn't run right. Spark plug is fine. When I adjust it to having the choke almost completely on, it will revv up, thought it seems to "hesitate too". It dies at idle though. If I open the choke it idles but bogs down and won't rev up. I don't know what the problem is. I don't suspect the idle screws because they're those kind that can't be adjusted without a special tool and my neighbor doesn't have on as far as I know, nor do I. If it comes down to it, I'll use a Dremel to turn those stupid screws into flatheads. But I don't know what the issue is. Anyone have advice? Thanks!!!

    -Tyler

  2. #2

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    Re: Craftsman 2 stroke 25cc string trimmer only runs on 80% choke

    Do those stupid screw and open up some.(counterclockwise).Dan

  3. #3
    tom3's Avatar
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    Re: Craftsman 2 stroke 25cc string trimmer only runs on 80% choke

    Get a hook and pull the fuel hose out of the gas tank, check the filter and the end of the hose for a crack. I did the dremel deal on my mixture screws and the housing and it really helps to keep it running right to adjust those. Mine are marked H and L for high speed and low. My trimmer has the noisiest muffler of any two stroke yard machine ever.

  4. #4

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    Re: Craftsman 2 stroke 25cc string trimmer only runs on 80% choke

    Just get the adjustment tool, they're cheap and easy to find online. Dremeling the screws can damage them and prevent them from sealing properly, making the carburetor impossible to adjust.

    Tom, what kind of trimmer do you have?

  5. #5

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    Re: Craftsman 2 stroke 25cc string trimmer only runs on 80% choke

    Quote Originally Posted by TylerFrankel View Post
    Hello! I am working on a string trimmer for my neighbors, which is a craftsman branded 2 stroke. Seems to be pretty new. When he gave it to me, he said it would start but promptly die. It did that. I changed the fuel out of it, took the carburetor sides off (both the metering and fuel intake diaphragms looked ok, felt silky), and nothing looked too dirty. Cleaned it up with some water, reassembled it and still doesn't run right. Spark plug is fine. When I adjust it to having the choke almost completely on, it will revv up, thought it seems to "hesitate too". It dies at idle though. If I open the choke it idles but bogs down and won't rev up. I don't know what the problem is. I don't suspect the idle screws because they're those kind that can't be adjusted without a special tool and my neighbor doesn't have on as far as I know, nor do I. If it comes down to it, I'll use a Dremel to turn those stupid screws into flatheads. But I don't know what the issue is. Anyone have advice? Thanks!!!

    -Tyler
    Thanks everyone! I'll try and adjust the screws. Lucky for me, they aren't labeled so I guess I'll just turn them around until it starts working If a dremel will damage it, then.... welll... I'll do it anyway and risk buying a new carburetor. It feels wrong to fuel the EPA and corporate greed.

  6. #6

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    Re: Craftsman 2 stroke 25cc string trimmer only runs on 80% choke

    Quote Originally Posted by tom3 View Post
    Get a hook and pull the fuel hose out of the gas tank, check the filter and the end of the hose for a crack. I did the dremel deal on my mixture screws and the housing and it really helps to keep it running right to adjust those. Mine are marked H and L for high speed and low. My trimmer has the noisiest muffler of any two stroke yard machine ever.
    I've looked at it, it looks ok to me. It can't be more than 2-3 years old, its very clean and looks new. The carb gaskets are pristine and the EPA screws tells me its not too old

  7. #7

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    Re: Craftsman 2 stroke 25cc string trimmer only runs on 80% choke

    The L needle is Longer and is the one closest to the engine
    The H is generally shorter and always closest to the air filter end
    The EPA carbs have a much longer taper section on the needle so generally their initial settings are 2 to 4 turns off sealed

  8. #8

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    Re: Craftsman 2 stroke 25cc string trimmer only runs on 80% choke

    The EPA doesn't make any money off the tools, in fact they would prefer if you didn't know the tools existed or where to buy them. However, they aren't able to regulate the Chinese manufacturers who mass produce them.

    Don't just mess with the screws randomly. First, begin with the H screw and open it (turn counterclockwise.) Then do the "L" screw the same way if it still hesitates when getting off idle.

  9. #9
    tom3's Avatar
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    Re: Craftsman 2 stroke 25cc string trimmer only runs on 80% choke

    Quote Originally Posted by primerbulb120 View Post
    Tom, what kind of trimmer do you have?

    Straight shaft Craftsman 25cc. Red, model 315.794470. All around good machine but not the best for in the neighborhood here. Tried to fit a different muffler on it but couldn't rig one up.

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