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  1. #1

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    120 Thunder tiger idle screw problem

    After about 1 flight the idle screw leans out to the point the engine dies. I have heard of screws coming loose but this one is turning in. Has any one had this problem and if so what is a good fix to keep it from turning?

  2. #2

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    RE: 120 Thunder tiger idle screw problem

    try new, stronger spring--if no workee gently deform threads of idle screw(pliers) still no workee buy new carb stock or Perry(Varsane?) 120 one strong motor--good luck!

  3. #3

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    RE: 120 Thunder tiger idle screw problem

    Thanks I might try that. It sure eats up a gallon of fuel in no time.

  4. #4

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    RE: 120 Thunder tiger idle screw problem

    The correct fix is to replace the "O" ring on the low speed needle
    Mr. Motor A K A Paul

  5. #5

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    RE: 120 Thunder tiger idle screw problem




    ORIGINAL: MrMotor

    The correct fix is to replace the "O" ring on the low speed needle

    I will try that first. I hope it works. Thanks

  6. #6
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    RE: 120 Thunder tiger idle screw problem

    Your carb screw is turning from vibration, nothing else. Balance the prop
    spinner and backplate. Getting the engine running perfectly with the proper fuel,
    glow plug, prop, and the carb settings will get it running smoothly.

    FBD.
    An engineer says.... "That will not work".
    A mechanic says..."Oh yeah, watch this".
    Old age and treachery will overcome youth and skill.
    Revver Bro #4.

  7. #7

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    RE: 120 Thunder tiger idle screw problem

    I changed the o-ring and the needle is staying put but I guess I will pull the prop and check it. I always balance be for i put them on how ever something is out of balance, I can tell by screws getting loose. The plane flew well yesterday and today with no dead stick landings. Something else, at part throttle or just below it does not run smoothly. It sounds like a chainsaw engine at idle. At full idle it is smooth. I tried adjusting low speed needle to smooth it out but that does not help. The transition is good from idle to wot so Maybe im makeing to much of it but I thought the engine was smooth at any rpm while flying when it was new. I had the head off a few days ago and noticed the last 3/16 of ring travel at the top of the cylinder was showing wear ''as in different color of metal''. Its not rough but its not the same metal as the rest going to the bottom of the cylinder. Is that common or is it time for a new cylinder?

  8. #8

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    RE: 120 Thunder tiger idle screw problem

    Do not deform the threads on idle screw...after adjusting, the metal threads on the screw will wreck the aluminum carb threads, making it junk. Capt,n
    I never met a engine I did not like !

  9. #9
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    RE: 120 Thunder tiger idle screw problem

    As long as the compression is ok, and the performance is good, don't
    worry too much about what the top of the cylinder looks like. The engine
    will let you know when it is ready for an overhaul. When the compression
    starts to go away, you will not be able to flip start the engine, and it will
    not want to idle as well as it did.

    FBD.
    An engineer says.... "That will not work".
    A mechanic says..."Oh yeah, watch this".
    Old age and treachery will overcome youth and skill.
    Revver Bro #4.

  10. #10

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    RE: 120 Thunder tiger idle screw problem


    ORIGINAL: Flyboy Dave

    As long as the compression is ok, and the performance is good, don't
    worry too much about what the top of the cylinder looks like. The engine
    will let you know when it is ready for an overhaul. When the compression
    starts to go away, you will not be able to flip start the engine, and it will
    not want to idle as well as it did.

    FBD.
    I have it on a coroplast that I built and its scary fast in all ways. After cuts and broken finger nails if my starter wont make it run its not going to.. No problem with the idle or starting though . The plane is 11 1/2 pounds and still goes up like a rocket. Thanks for the help.

  11. #11
    m.gramling's Avatar
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    RE: 120 Thunder tiger idle screw problem

    what prop and muffler you guys running on these. I have a TT1.20 and love it.
    Everybody wants to go to heaven, but nobody wants to die...


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