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ys 120 excessive smoke

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Old 05-19-2017, 11:30 AM
  #1
larryjd
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Default YS 120 Excessive smoke

I have an older YS 120 SF. I have just replaced the front and main bearing. I also replaced the fuel regulator diaphragm. I am using Wildcat fuel with !5% nitro with 18% lubrication. The fuel tank is pressurizing OK. (it will actually hold pressure for days at a time). I am running a 15X8 prop. The performance of the engine seems pretty good. It idles well at 2000 rpm's and runs up to 10000 rpm's. Transition from idle to max seems pretty good. Adjusting the high speed needle at 1 1/8 turns seems to work OK. The regulator screw is adjusted at about 1/32" below flush.The problem is that I seem to get excessive smoke out of the exhaust at mid to high rpm's. If I try leaning the needle any more, the rpm's just decrease. I wondering if I have a bad piston ring or some other problem. Does anyone have any ideas?

Last edited by larryjd; 05-19-2017 at 12:12 PM.
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Old 05-23-2017, 06:16 AM
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Four Stroker
 
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Adjust for max rpm on the ground and richen (turn out) main needle 3 clicks.

Smoke is the oil burning/vaporizing in the muffler. Try a YS 20/20 fuel. OR 30% heli fuel. How much is too much smoke ?
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