[NSRCA-discussion] OS 1.40 RX mid range loading up problem

[Bob Harden]

Hello All,

I need some of your expertise.  I am having trouble with my OS 1.40 RX loading up in mid range.  The engine has 5 flights and approx 2 gallons of fuel through it.   I am using an APC 16 x 14 prop,  OS T-6010 Tuned Silencer, tried the A5, #8 and type F plugs (no difference), Magnum fuel 10% nitro with caster/synth blend, pipe set for 8000 rpm, and using the short needle valve.   The low end idle adjust screw is adjusted all the way to the lean (all the way in) which is necessary to idle smoothly.  Transition quickly from idle to max throttle isn't too bad but slower than I would like.  If I set the throttle at 30% to 50% it loads up and and slows in RPM.  In transition from mid to high throttle the  engine vibrates and burbles for 3 -4  seconds before it clears and comes on the pipe, it has even stopped running a few times.  I have read that some folks use the longer needle valve and higher nitro to minimize this problem, but I haven't tried that yet.  From those of you who have experience with this, what is going on, and what are my options?
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