Ho ho ho!! You're getting there!

Sounds like you're still over-priming at startup. Just bring the fuel, when you turn the prop by hand, up TO the carb...that'll be all you really need.

Hint: I had 2 setup probs with my enya's, both related to the exhaust, believe it or not. I was tired of having the loudest plane at the field (ineffective stock muffler) so I bought a Davis Product's super-quiet muffler. It looks like a cannon - big and black. And then it wouldn't run right - rich as all get-out. I had to (my only engine mod EVER) slightly drill out the airbleed hole (after removing the bleed-adjustment screw, thankyouverymuch) to allow more air in there and lean the idle mix - the muffler created more backpressure, forcing more fuel in than the original bleed-hole was capable of mixing. Your muffler-exhaust redirector *could* be adding to your back-pressure, doing the same thing as that big ol' Davis muffler. Leave it off for now and just clean the plane more. This is a known thing, by the way, with all engines.....add more exhaust pipe? Adds more exhaust pressure and 2-strokes don't like that.

The other one was a cheap-o Pitts style muffler for my Goldberg Cub (yes - a Goldberg Cub, either full- or clipped-wing, will fly perfectly on a bushed .40 - AND floats, too!). It had two exhaust outlets - yep...REDUCED the back-pressure to the point that the tank wouldn't pressurize...this took many dead-stick landings to figure out. Heh - I stuck a dowel in one of the exhaust pipes...fixed it.

Sounds like you're still too rich. 'Tweaking' the high-speed isn't something you put off until you 'have time'. It's something you do every time you go to the field! Leave the needle where it was last time, open 1/4 turn or so, start 'er up, then lean down to match today's weather conditions. It takes oh, about 30 seconds.....and is a normal 'first-flight-of-the-day' thing to do.

If it's idling OK, but still burbling and spitting when you give it throttle, lean the idle bleed out some more...not much..turn it in 1/8 turn or so, then see if it will still run and idle. Normally, with this engine, a rich idle will be good and sound OK, but guess what? Hit the throttle and it croaks..... lean out the idle just a touch, restart, etc. As long as the carb barrel is closing as I described earlier, you'll set your idle speed with your radio, and it should die when you pull the throttle and trim all the way back. Long-term idling as you described? It's a recipe for disaster and stalling at inopportune times. Start it, tweak it (first flight), taxi out and launch.

I would fly at 1/2 throttle a LOT - but that was after the engine was set correctly. do your fine-tune tweaking at home - it's frustrating to do at the field when you'd rather be flying, and you might take off with something 'not quite right' just to fly...then dead-stick it in.

And yeah - for a bushed engine, they're plenty strong. Mine, after 3 years of casual flying, would still hover my Balsa USA Stik .40 (the perfect trainer) at 4.5 pounds on a 10x5 prop for 10-15 seconds or so...it wouldn't accelerate up like a 3D plane, but it would hold it. Good enough for me!

Surface radios are supposed to be on a different set of channels - 75MHz or 27MHz, generally. But a Walmart toy is gonna hvae cheap, and possibly frequency-sloppy, radio gear. Almost any radio will twitch madly if the transmitter is off. Once the Tx is on, however, all weirdness should disappear... If the guy and kid show up again, invite 'em over, tell 'em what's going on and:

#1 Tell 'em it's a recipe for disaster to bring stuff like that near an 'official' R/C field
#2 Test it!! Have 'em in the pits (tell the other pilots what's afoot) and see what happens - show the perps what they're doing to you guys!