can you get to listen to another two stroke? They do sound loud at idle compared to a four stroke, so the noise may be normal. No point panicking until it goes pop eh?
As for fouling the plug, it's either a badly setup carb, or the ignition circuit. Try swapping the coils over to see if the fault changes to the top cylinder.
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball