dune buggy dies in 5-10 min

i have a dune buggy..an early 70's model motor..and i dunno whats wrong.  I can get it running for about 5 or 10 minutes and then it just dies on me.  Ive replaced coil, fule line, fuel filter, rebuilt carburator and so on,.  And just recently a couple ppl have told me it sounds like voltage regulator or is in the electical part some where....possibly a dead short somewhere because when i shut it off i dissconect the battery cause it will be dead by the mornin.  im not a mechanic and dont claim to be..but any ideas or tips will be greatly appreciated