Same things make bikes run as cars, so they're fair game.
Question 1 - How's the sparkplug look? Same for the air filter. Either of these would fubar your mileage.
Are you smelling gas while you ride? Look for a leak. This could also be from a stuck float if you have a carburetor.
If it's new enough to have fuel injection, you might have to put it into a shop.
Question 2 - The fuel light should be triggered by the float that also serves your gas gauge. If it's not working, check the
wiring to the sending unit first. If still no luck, drain the tank into a gas can & pull the sending unit, the float may have gone
bad.
Let me know what kind of car (or bike) you're working on, everybody builds them a little different.
If anyone reading this topic recognizes a problem, feel free to speak-up.