RE: Tuning Problems
Scott,
Is your plane's fuel-tank set at the right height?
The correct setting is: tank center-line level must be identical to that of the carburettor's jet, with the model in level flight attitude.
Also, is the tank as close as possible to the engine and is fully isolated from any airframe vibration, using at least ΒΌ" thick Latex foam?
If any reply is negative then you had just found the cause of your misery...
And as to the 'ring ding' sound on over-run... Just ignore it.
Detonation could damage your engine, but it will happen at high-throttle setting, if you are running the engine too lean, or with too large a prop.
This is what is popularly called a 'lean run', which in essence is excessive 'ignition advance'.
It is more often described as 'frying egg' sounds...
In any glow engine; since a leaner mixture will ignite sooner and will combust more rapidly, compared to a richer mixture; the needles are actually the 'ignition timing control'...