Hello All,

The engine mystery was solved today!

The root cause of all problems was simply a very small rip/cut in the spark plug lead insulation. The small cut exposed part of the spark plug lead internal wires, which effectively diminished the strenght of the actual spark. This diminished spark strenght was likely not enough to cause proper combustion at the higher throttle settings.... Hence the backfires.

Moral of the story is to carefully protect all wires related to the ignition system from chaffing and vibration.

RCIGN1... sorry about the confusion with my statements about timing. I simply mis-typed.

RTK... it is definetly a Syncrospark setup. Not a mechanical linkage.

Thank you all for your very helpful suggestions.

Took the Giles to field today... and it ran like a champ.

Now if I could only learn to fly better.

Cheers,

Marcus.