I would be interested to know what the ding - ding - ding bouncy sound means though because it's quite distinctive when it does it ... to lean, too rich, overheated ?
the last time I heard that type of noise was when I was a newbie and I warped the piston in my first OS 50 when I moved up to 30% nitro and my engine was way too lean. if your engine is shimmed for 0% Nitro you may need to add a shim for 15% Nitro.
example> the large Super Tiger's, 23cc and larger will not tune out well at all with over 5% Nitro.
just about the best thing you could do for that engine would be to buy an OS Heli carb for it if one would fit it.
no difference other than the engine just cutting due to fuel starvation.
this could "could" be because the engine is still not loaded correctly. I have seen this on planes too that had props on them that were very much too small for the engines. one of them was a GMS 61 that had a super light wood Zinger 9x4 on it, the engine would start but once up to lift-off speed the engine would stall. after 3 hours of the owner working on it I walked over and saw the 9x4 prop and told him to change the prop. once changed to an APC 12x6 the problem was instantly gone for good.
if you put the engine on a stand and run it with a 10x10, 11x7, 11x8, 12x4, prop on it you may see a well running engine.
Jim