My kohler 4.5 generator starts then dies unless you hold the start button

Hi,
Kohler generally has manuals online, if you know the model number. I might steer you somewhere if I did. I would not rule out fuel, but..
Peace,
Clarke

Thanks,I have checked the fuel,if I bypass the control system it will run fine,the relay that is feed by the voltage regulator & the gen. windings is receiving intermittent power,when I feed 120 volt to the relay everything works but the output power jumps from 68 volts up to 139 & anywhere in between,I think it might be the voltage regulator

Hi,
Sight unseen, only written description and model unknown, I would say you may well be on the right track!
Peace,
Clarke