Engine is noisy with a whirrr

I have a 2003 shadow spirit. I bought it used with 23 k on it. The engine sounds vey noisy and with the clutch in there is this loud whirr that I hear even on the hyway. When I accelerate hard it sounds like theres alot of (very tinny) sounds coming from the motor. Other spirits sound alot quieter There are other "rattles" coming from the motor. Other than that seems to run fine, just cant take the noise anymore and I'm worried that it might be gearbox trouble. I use mobil 1 20 / 50 synth oil for bikes. The bike looks new and is in mint shape but I'm suspicious the previous owners might have driven it a little hard. Any suggestions as to what it could be? Thanks,, Sixstringsam