How do you change the plunger attached to your fuel gauge

The sending unit for the gauge would have been attached to the fuel pump in the tank.

The fuel sending unit rod was bent during the instalation giving you the false readings. This is the thin metal rod that attaches the float to the sender.

Try filling half full then reverse pretty fast then slam on the brakes or drive forwards and slam in breaks may push the plunger to correct position if not then have the mechanic pull back out and fix the gauge arm"looks like a bent coat hanger with a plastic piece on the end"

To bleed the fuel system you need to remove the plunger on the fuel rail. It is located where you hook up a fuel pressure gauge. Once it is removed have someone cycle the ignition key to the KEY ON ENGINE OFF position, or the accessories position, 2 - 3 times this will get all of the air out. Also place a tube on the fuel pressure fitting so that fuel doesn't spray all over the place. Once this is done replace the plunger and cycle the key 2 - 3 more times. This will ensure fuel is at the injectors

The problem is caused by the fuel sloshing around in the tank and the fact that Harley does not use a "dampened" gauge. The sending unit is a float attached to a rod inside the fuel tank. As the float rises and lowers, it changes the resistance of a variable resistor in the tank. The resistance is read by the gauge and converted into a reading that approximates the level of fuel in the tank. The reason the gauge is not dampened could be any number of reasons. Either Harley wanted to use a cheap gauge or a dampened gauge might allow you to run out of fuel because it reads the level of the fuel too slowly. In small tanks like the ones on motorcycles, this could be a problem. I know of no way to remedy the problem without changing the gauge and sending unit.

Good Luck
Steve

there is a plunger in the fuel tank that controls the gauge, have a mechanic check that, and worst case have a new gauge installed. and if you dont want to do any of those. just keep an eye on the amount of mileage driven and refuel as necessary.

you need to know how much fuel is actually getting to the injectors. if it's throttle-body injected you should be able to observe a basically uniform conical fuel spray from below the injectors in the throttle body. if multiport injected, you can't see injector spray, but you can attach a fuel pressure gauge to the schrader valve in the fuel rail to see if the fuel pump is putting out adequately. if you don't have a gauge, my favorite redneck method (this is technically a bad idea, so please use all common sense if you do this...no smoking, no open flames, keep all spark plug wires attached, etc.) is to depress the plunger on that schrader valve w/ a small screwdriver for about half a second; if you get pretty wet w/ gas then your pump's probably ok, but you might have a problem where the injectors aren't getting the proper signal from the computer

Youre gauge is controlled by a plunger in the fuel tank which is attached to the sensor and the fuel gauge. it sounds like when the plunger goes down half way its either getting stuck down lower then it should. Needs replacing. Any mechanic can do this install for you.

did you recently change the fuel pump? If so you needed to change the wire harness thats attached to the fuel pump, then if not, your floater need to be replaced inside your fuel tank.
How do I know? from experience.

Replace the fuel pump and sender assy