Originally Posted by Wakko47

Bike sat for years, replaced all of the internals in the tank, including sending unit. The fuel gauge now reads low, and will trip the light while there’s still 1.5-2 gallons in the tank. I know the gauge is resistance based, is there a known bottleneck connector that could be the culprit?

Originally Posted by hattitude

Is it carb or EFI.....By "replaced all of the internals in the tank, including sending unit" sounds like we are talking EFI, but you don't say for sure... Even the carb bikes have (internals) and a sending unit in the tank....

Anyways, if you removed the tank for the internal parts repair, there is a connector on the left side (primary side) of the tank, along the top frame backbone. The fuel gauge wires run through a tube in the tank, out the bottom at the left front, and connect to the bike's harness at the above mentioned connector....Those connector pins can get bent, leading to improper contact and cause a bunch of fuel gauge issues. I found that out the hard way...

If that connector was handled (removed, pushed, pulled, or prodded) during the replacement of tank internals, I'd check that connector first... it's free.

The only other thing that pops into my mind, is both Carb & EFI sending units have a float, at the end of an arm. As it moves up & down with the fuel level, it sends signals to the gauge on the tank volume. If the gauge is working properly, except for it is not accurately and consistently reporting low volume, that float arm may have been bent during installation.

Good luck with your diagnosis and keep us posted

Originally Posted by adammarcos

Anyways, if you removed the tank for the internal parts repair, there is a connector on the left side (primary side) of the tank, along the top frame backbone. The fuel gauge wires run through a tube in the tank, out the bottom at the left front, and connect to the bike's harness at the above mentioned connector....Those connector pins can get bent, leading to improper contact and cause a bunch of fuel gauge issues. I found that out the hard way...