I think what is happening is that there is a wire or wire switch connection spot that is bare wire and touching any metal frame or handle bar part. usually happens in handle bar switch [its a tight fit between handle bar switch connection and bar . this ground will case excessive current flow and trip out thermal C.B [disconnect head light high beam switch from handle bar , zap strap it dangling from bar , ware rubber gloves and look at switch, operate switch , observe results , if no conclusion can be obtained then get a factory manual and look at wiring diagram for head light circuit after breakfast on the back porch and during coffee. study it for 3 cups of coffee . you are now ready to trace the circuit on your bike and use a multimeter to test for grounds by opening the circuit some where and testing the open connection part coming from the positive side of the electrical flow through the meter set on ohms or my favorite the audible setting that goes beep and the other meter lead going to a nice shiny bolt that is screwed into the frame or bare metal . this message came from Canada Nanaimo B.C