Hallo!
The problem is usually a too lean setting!
I have never heard of or experienced that the clunk could get "stuck" against the tank wall so no fuel gets through to the carb!!!
That the engine starves is because of too high G pressures!
Either make the turn /loop larger or open up the fuelneedle somewhat!
But first you have to have a good tank and tankinstallation.
The best tank available are the Japanese Tettra "bubbleless" fueltanks. We use them in pylonracing all the time.
Regards!
Jan K
Sweden