CBR600FN running problem.

[Suntan Sid]

Went out for a run , early Sunday morning, on my CBR600FN.
I did a couple of miles and felt it wasn't runnig right a low rpm, rather than risk breaking down, in the middle of nowhere, I turned round and headed home, felt like it was only running on three at lower revs.
Got home, pulled the air filter, which was spotless, but blew it through anyway.
Pulled the plugs, numbers 1,2 & 4 were spot on, number 3 was black!
Fitted a new set of plugs an hour ago, still running the same.
Quite a strong petrol smell from the exhaust
I suppose my next move will be to pull the carbs and give them a clean.

Bike's done about 45k miles, no rattles from the motor, still idles well but has dropped a hundred rpm, (not lumpy at all), it still revs out easily to the 13000 redline.
Anyone had similar problems with this model?
Any ideas much appreciated!