Has the bike been left for a while before using? If so it could be the petrol is off, adding more petrol will not make it any better. If no luck cleaning out the carb, try emptying the tank and carb, and putting fresh petrol in.
I have a 600 fazer on a 2000 plate, it has been laid up over winter with the occasional 10 minute run. On using a couple of days ago the engine was roapy between tickover and 3000 rpm. Seems like a cylinder not firing correctly. I gave it a blast up my local bypass but no better. It had been about 4 weeks before its last run. Any idea's?