What makes you think it is the pickup?......never heard of them going faulty....from what you say the engine runs, and that implies the pickup is working, as is the CDi unit, is it that you have a weak spark?, if so i'd check the coil/connections/earthing/plug cap/plug......i suppose it's possible that the rotor is demagnetised but thats very rare on these bikes too as far as i'm aware, is it charging the battery/running the lights ok?....that would indicate the rotor is ok.