Well that's not much to go on...
Start but not run?
The fact that it will supposedly start says the electrical may be ok, but if they mean "not run" in that it may eventually die, then it could be a stator problem.
So.. where to start.. put the bike back together and see what it does do then. With a charged battery, enough fuel to do some tests and all other fluids filled turn the key..
Does it start but sputters? Could be the carbs need cleaning or maybe as simple as one of the floats or needles are stuck.
Without more to go on it's hard to suggest where to start other then.. get it started
Patriot Guard Rider
2000 VN750 Sere (Serendipity)
1990 GL1500 (Ole Blue)
1986 VN750 EVie (project bike, heavy custom)
VROC # 11628 / 25000-H
ARVROC # 12 Coordinator and Crowd Control
OKVROC # 18 (H)
TNVROC # 45 (H)