With bike pinging (basically high compression is causing pre-ignition, that metallic pinging sound is mini-explosions of the fuel mixture lighting off before the spark actually is to fire the mixture...sapping energy from the actual power stroke. Do check your fueling system for obstruction (drain the fuel bowl at plug, the gasoline going into a clean glass. If cloudy, rusty or plastic bits, the fuel tank liner could be flaking off and plugging the inlet fuel sock/screen in the fuel petcock assembly. Is the fuel petcock vacuum operated (you will see a skinny hose up there and 4 screws covering the diaphragm shutoff valve). May want to get a service manual and check out that carb...also check the self help section to familiarize yourself with the carb setup you have.