You will require access to the end of the alternator from the drawings on the pramac site the alternator looks like it could be made by mec alte spa if so there are spec sheets on their site for the alternators, remove the end cover of the alternator and there should be a bridge rectifier in there which will need testing also the spec sheet should give the resistance of the coils so you can check them you will need info from the target="_blank">herehere