Black is NOT a good colour. If your plugs are black then the engine is not burning all the fuel going in - the jets in it are probably too big, though there may be other problems of course.

Do you have access to a rolling road (also known as a dyno) for motorbikes?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball