Hmmm...is this the newer .46 or older?   Use fresh fuel.  Try tuning all the way rich and lean.   Tune with the high and low speed needles, maybe the idle needle too. <div>
</div><div>Yeah, an air leakk is always a possible cause for bad performance.  Get gasket sealant from an auto shop or anywhere.  You can seal the back plate, and where the carb connects to the engine (won't hurt engine even if it doesn't help).  Check fuel lines for leaks.  Disconnect hoses from engine and blow air through.  Make sure the glow plug glows real bright and is not damaged.  You will have to use process of elimination.  Of course if it is an old engine maybe the internals are really worn down?</div><div>
</div><div>In my experience nitro engines are very finiky by nature.  Never ran as consistent as a gasoline engine, though perform great.</div><div>
</div><div>I have the newer .46 engine with black cooling head...I have noticed the sputtering sound though didn't notice any effect on performance.  Try messing with the low speed needle, that might make the sound go away.</div>