All motorcycles that I had I had a voltmeter onboard and all I had trouble charging systems :
Aprilia RST Futura problem with brown conector, connector between alternator and rectifier melted(imperfect contact) - rectifier faild
Honda VFR 800 Vtec : faulty alternator- replaced, rectifier OK
and now ST .....oK I charged the battery I use a Optimate 6, battery is good, I checked and cleaned battery contacts and fuse of 30 Amps, no starting problem...bike starts well for now, but as I said the battery is full charged ! Charging values remained unchanged 13.5 V light On and 13.9 V light Off...fans started, light on 13.2-13.3 V something is wrong In my opinion...Next day I do get a spare battery from a friend and I'll try again, I hope to have another result and not having to remove the alternator....possible to have imperfect contacts elsewhere?