Troubleshooting problems of this type on a bike I can't even see is like playing poker blindfolded. But I can tell you that most of the time, a complete power shutdown is the result of a poor battery-cable connection. On older bikes, the ground cable often is at fault or engine rather than at the battery end. Over time, corrosion around the cable's anchor bolt, often aided by normal engine and road vibration, can cause the connection to lose its normal metal-to-metal contact, resulting in a complete loss of electrical power.
Then, the same kind of jolt or vibration that caused the cable to lose contact in the first place reestablishes continuity, allowing the electrical system to function once again. So, the fix is simple: Carefully check, clean and tighten all battery-cable connections.
The problem may be with the ignition switch. The metal contacts inside that old switch may have either loosened or corroded, causing an occasional open circuit that shuts down the electrical system just as though you had turned the ignition key to the Off position. Ignition switches can't easily be repaired, so if yours proves to be faulty, you'll have to track down a new or good used one.
Thanks guys, it was the battery-cable connection, but the ignition switch was also in a terrible state.
Michael
I have a old Honda Magna V30. Sometimes when I am riding, the motorcycle stops and all of the lights go off, then all of a sudden everything starts again. It has done this twice this past month so far. About a month or two ago, the engine would just kind of sputter, making me think that maybe the fuel line was crimped. Now, it just totally shuts off and comes on again.