Chosen Solution
What would cause my 2002 Harley-Davidson Ultra Classic to start sputtering and throttle body backfiring after using 1/2 of a full tank of fuel? I refuel to full and it runs fine.
Don’t know if this is true for HD, there has to be a vent in the top of the fuel tank to let air in as the fuel level goes down. If this vent gets blocked, the area above the fuel forms a partial vacuum. This restricts the fuel supply to the engine. Test , when you experience this problem, open and close the fuel cap and if there is a blockage, the engine will run normally.
