When you turn?
Are you leaning the bike, or turning the handlebars when it sputters?
If it happens when you turn the handlebars & the bike is more or less straight up & down, I would suspect an electrical problem. Look for a wire that has the insulation worn through & grounding out against the frame, forks, bars, etc.
Does the bike still have the center stand? If so, place bike on center stand & start. Allow the bike to idle & slowly turn the handlebars from steering lock to steering lock. If it dies, stop moving the bars & look at the wiring.
J.
PS. Buy a nice helmet & wear it. Beware of drivers from Sun City.