.46 towerhobbies engine running bad

Hi. I recently bought a towerhobbies .46 bb abc engine, and Its not running very well. First, the sound it makes is not as even as ALL the
other engines, it sounds as if it were coughing once every 2 seconds or so. Second, when I start the engine the rpms it gives with the plug battery connected are way higher (20% or +) than when I disconnect the plug. Ive tried NEW A3 and A8 plugs, but they show the same behavior. I can fly with the engine but Im afraid it will stop while flying.
I have the following questions: Is the engine supposed to change rpms if I plug the clip while at max power? When the engine is at mid-power and I unplug the battery the rpm change is much less obvious. The manual recommends using "long glow plugs", would OS's A3/A8 be ok ? could this behavior (uneven sound ) be due to a bad break-in?
Thank you for you time and help, I hope you can help me.
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No.
Try a McCoy RC 9 or 59.

Possibly. Or it might not be broken in yet. It sounds like it's running rich. Go ahead and lean it out to a smooth sound. ABC/N engines need to get up to operating temperature to properly break in. If not hot enough during break in, premature wear can occur due to improper liner expansion. Dr.1 Driver "There's a Hun in the sun!"
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You may be running the engine too rich. Try leaning it out a little more. Unclip the glow lead then adjust it until the RPMs peak then richen it about 1/3 turn.
When properly adjusted, an decrease in RPMs with the glow driver removed means the nitro content is too low or the compression too low. Lower nitro usually requires higher compression.
-- Paul McIntosh http://www.rc-bearings.com

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