When I owned a Yamaha VStar, there was no other fuel indicator other than watching your trip odometer. I can't tell you how many times I ran out of gas and had to switch to reserve. The problem was that you would get about 2 to 3 seconds notice before the engine would stall. If you are in motion in traffic flow, there was no choice but to very quickly reach down and switch to reserve, give it a few seconds for fuel to reach the carbs, and start it back up while still rolling. It was bad enough having it happen, but if I would have needed to find neutral to start it back up, I'd surely be roadkill a long time ago. Yeah, I know...after one time, I should have paid very close attention so I didn't have this happen.
Anyway, I rebuilt the carbs on that bike, and went as far as making modifications to the carburetors themselves (such as drilling holes to larger diameters, etc...don't ask), but after getting everything to go back together what seemed like perfectly, it started right up but I could not get the bike to stay running once I put it in gear. I tried over and over. It started perfectly and no matter how much I revved the bike, as soon as I put it in gear it stalled immediately. I was in a total panic. I ran up to my computer and typed a message into the VStar forum. I was lucky that someone answered me immediately. All they had to do was respond with "Did you put the kickstand up?" Wow, did I feel like an idiot. I felt better when I realized that after everything I did, not only did the bike still run, but a HUGE change in performance by letting some more fuel flow through the carbs.