Because the glow plug isn't directly on the bottom as in most 2strokes, the 4strokes don't tend to be as problematic inverted. Still, use a good plug (OS F) and the most important item to ensure success is PROPER TANK PLACEMENT!

The tank centerline should be about 1/4" BELOW the carb centerline. Get as close as you can to that and you can likely adjust the richness out. Too high and you will always need glowheat if you ever expect a reasonable idle.