Sounds like the carb is set up wrong.... Possibly running too lean at top end and too rich at low end.

Too lean at top makes the cylinder expand excessively, reducing compression by allowing the gasses to pass between the piston and cylinder. This makes starting very difficult. The high temperatures are very bad for the engine too.

The dieing out with sudden throtle reduction (and usually also dies when you suddenly accellerate after idling for a while) normally shows that the engine is "quenching" the plug. The momentum of the propellor can increase the vacuum in the intake on sudden throttle reduction, pulling more fuel than needed, and the result is fuel droplets going into the cylinder, rather than a fuel-air vapor mix. A droplet hits the glow element durring intake, and its "lights out."

Its probable that an experienced modeler could readjust the engine in less than 5 min.... This is one place where having someone else who has done it before helps a LOT.