one the wheel that you think the bearing is bad, is it a front wheel?
if so, make sure the screws that hold whe steering knuckle to the "C" hub are both there. the one on the bottom can fall out if it gets loose.

i had the backdraft for awhile, and recall that the tank would still be 1/8 and yet i would have to add fuel for it to run.

the fuel in the tank can move around alot, allowing air bubbles if the fuel level is low.

but it wont hurt to clean everything up and check the fuel tank and lines over for and damage or wear.