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Thread: Stihl 088 carb problem

  1. #1
    TreeHouser Sponsor Raj's Avatar
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    Default Stihl 088 carb problem

    My 088 was acting up. kicking back when cold. Then it would loose power and die in a cut. It would idle no problem. When reving no load it would sound great, no sputter or hesitation. Spark plug is a nice brown ashy colour with some light black oil around the threads, I do run 40:1 oil.

    I put in a carb kit but there was one small brass plug I didn't change and a screw in nozzle that I didn't touch.
    Ran good for a few heavy cuts.

    Now today it seems to over rev, the speed doesn't match the throttle and when you release the throttle it will drop RPMs to a higher idle, then within seconds rev down to idle. Saw will idle and rev no problem, no cutting.

    Whole carb is not available in my area.

    Any idea what I missed when i put the carb kit?
    Peter

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    Treehouser Sponsor pete mctree's Avatar
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    Almost sounds like an air leak or split impulse pipe. I presume you have pressure tested the machine?
    The 200t carbs used to develop a similar problem - welch plug was often the cause (that and the accelerator pump, which I don't think the 088 has). It may be the issue allowing air in. Simple way is to use something like nail varnish to seal it & then test again.
    To gain that which is worth having, it may be necessary to lose everything else.
    Bernadette Devlin

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    TreeHouser Sponsor Raj's Avatar
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    No pressure test yet.

    I did discover the new diaphragm was bent up. Hope that's the issue. Dealer has a new kit coming tomorrow, otherwise I'll try to bend it back.
    Peter

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    Rodent Aviator Sponsor Skwerl2's Avatar
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    Check your fuel and impulse lines for cracks. Sounds like it is sucking air.
    -Brian

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    Does it make a pulsing sound too after you let off the throttle? We have saw like that. I keep forgetting to richen it. It doesn't kick, but can be hard to start and keep going at times as it leans out and dies at idle.

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    TreeHouser Sponsor Raj's Avatar
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    No, just a smooth engine bog. Idles fine and throttles great no load.

    Thanks all. Going to make plates for pressure testing tomorrow. Dealer has some replacement parts for me. Hope I solve this. Damn milling is backlogged.
    Peter

  7. #7
    TreeHouser Sponsor Raj's Avatar
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    Pressure test. Held 6psi for more than 5 minutes. Pressurized through impulse line.

    Metering diaphragm was bent up bad in the carb kit. It didn't push the meter arm down far enough?

    Edit. Saw held a vacuum no problem.


    Click image for larger version. 

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    Peter

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    Treehouser Sponsor pete mctree's Avatar
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    The damaged diaphragm is not going to help at all - has to be the next thing to do, even if it just eliminates it.
    To gain that which is worth having, it may be necessary to lose everything else.
    Bernadette Devlin

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    TreeHouser Sponsor Raj's Avatar
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    Dealer got a whole new kit for me, sold at cost because of the other new kit had the bent diaphragm.


    Edit: cylinder compression easily reached 150psi.
    Peter

  10. #10
    TreeHouser Sponsor Raj's Avatar
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    A Facebook page mentioned that cracks tend to develope in the plastic angle fuel inlet, sucking air. Seems it's not a separate part. Mine has a small crack. What can be done? Rubber extension?

    Click image for larger version. 

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    Peter

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