The Tiger is all back together with a shiny white hood. I found nothing wrong with the carburetor or accelerator pump diaphragm — that was new. Several people have suggested that a spark may have ignited hot paint fumes. Who knows, but I hope that never happens again.
I ran the engine in the garage with the hood up last week, and it ran beautifully. Today I drove it without incident. I kept the hood slightly popped just in case, and put it up when I parked in order to vent the heat before the return trip.