Carby problem fixed
Thanks Geoff, Ian and Ross for your helpful suggestions.I had the carby bowls cleaned at the factory and they contained fine particles of dirt as well as some watery sludge.I also replaced all fuel lines beyond the on/off taps and inserted an additional fuel filter before the gascolater.This seems to have fixed the problem as no leaks were evident after a couple of test flights.It looks like it was a dirt issue all along.
Cheers Dick McCoy