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My 038 Magnum has a mysterious symptom

Discussion in 'Chainsaw' started by stihldragon, Jun 18, 2019.

  1. stihldragon

    stihldragon ArboristSite Operative

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    I got this saw from its first owner, a home owner. It's got low hours and it's been garage kept in it's carrying case. I traded my ms290 and a Toro push mower for it. Wow! Whata deal. It's twice as powerful as my ms290 was. Today when I was cutting a tree with it, as I pointed the saw down, it died. I quickly brought it level and it came back. It's cutting off when you aim it up or down and it came back. What does that symptom mean, intake boot leak?

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  2. Mad Professor

    Mad Professor Addicted to ArboristSite

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    Look at intake and impulse.

    I've also seen ignition or coil wire routed so it gets pinched, then insulation wears and that will short.

    From there fuel line/filter and carb.

    Seals are usually leaning left/right.
     
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  3. stihldragon

    stihldragon ArboristSite Operative

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    I thought it acted like a spark fail moreso than an air leak. Thanks for the advice, I'll look for an issue there. I'm supposed to be using it for a big job today.


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  4. pioneerguy600

    pioneerguy600 Lost in Space Staff Member

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    More likely to be fuel pooling in the manifold, carb set too rich on the H screw or the carb is flooding a bit from a stiff metering diaphragm. When I have a saw exhibit these symptoms the carb gets pulled, cleaned and re kitted.
     
  5. stihldragon

    stihldragon ArboristSite Operative

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    The area between the cylinder and the tank handle is very dirty. I'm going to separate them for cleaning and replace the the intake boot and impulse line while I'm in there. It's a 1980,s model so it needs rubber replacement by now. Plus, It's really soft and week feeling.

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  6. Mad Professor

    Mad Professor Addicted to ArboristSite

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    Would that show up just checking the plug, showing rich condition? Besides diaphragm, sounds like needle/seat could be culprit for too rich.

    Would not H- rich make it run like a dog anyway and have exhaust carbonized/oiled up?

    Just some thoughts.

    I have seen the pinched wires on 038s. Either bad routing and/or worn out AV buffers.
     
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  7. HarleyT

    HarleyT Tree Freak

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    Look at the fuel line...

    Look for cracks, and see if the part in the tank has become soft and gummy.
     
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  8. Mad Professor

    Mad Professor Addicted to ArboristSite

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    When you do that bend the segmented sections. Sometimes a crack will hide between two segments and can't be seen unless hose is bent.
     
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  9. TheTone

    TheTone ArboristSite Operative

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    Very true. I also like doing the bending under pressure and vacuum and watching the gauge.
     
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  10. stihldragon

    stihldragon ArboristSite Operative

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    The cause of the mysterious symptom was the high screw on the carburetor was maladjusted and a quarter turn counter clockwise made it run properly.

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  11. Mad Professor

    Mad Professor Addicted to ArboristSite

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    Thank pioneerguy600!

    Clean up AF, sharpen chain, and fine tune it in a full cut
     
  12. Yotaismygame

    Yotaismygame Juiced Saws #GetJuiced

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    Agreed. Also if the carb was gone through and the metering lever set too low you'll get that exact symptom. Did that once early in my saw career (lol) and it took me a lot of testing and parts swapping to figure it out.
     
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  13. Mad Professor

    Mad Professor Addicted to ArboristSite

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    Harley, in back seat of a 65 Dodge? :thisthreadisworthlesswithoutpictures: :ices_rofl:
     
  14. stihldragon

    stihldragon ArboristSite Operative

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    I adjusted the H screw just to see what would happen and at first, it seem to be running better. It didn't seem to be too lean. That symptom didn't come on right away. It started later in the day. When I adjusted it back the way I had it, it was cured. Intake, impulse, and coil were fine.

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  15. stihldragon

    stihldragon ArboristSite Operative

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    The fuel line on my 038 super parts saw is cracked above the filter. I robbed the oiler gears from it to fix the Magnum. I'm ordering parts to rebuild it soon. It's in the black box in the pic[​IMG]

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