Trying to figure out why the max I can put into my tank is right around 3.5 gallons when it should be a 5 gal tank. What could some of the possibilities be? The gauge might be reading wrong... I am going to try and run it completely empty in the next couple days to see if that's the case. But every time it shows empty I can only get 3.5 gal in it.

 

The tank gauges are notoriously inaccurate. Me and OCT1949 are the only ones to claim relatively accurate gauges. I swear by the trip meter. I can go about 170 miles before the light comes on.

 

+1 on bad gauges, I'm on my third one. This one seems to be pretty good, you guys can add me to the list of decent gauges. Probably just jinxed it though. Anyway, if its EFI, the light should come on with about 1 - 1.5 gallons left. I've run mine well beyond the light hanging on E and she still only took about 4.5 gallons at fill up. I'd bet the gauge is off. Mileage-wise, I start lookin at about 175, and sweating at about 200.

 

That was the only logical explanation I could come up with. Thanks for the responses guys

 

The tanks hold 5+ gal, and the gauges are usually off but consistently off. You can adjust the floats by bending the arm, but in all honesty why not live with it and just figure when you are showing empty you still have another gallon and a half in the tank.
Keep an eye on your gas mileage and use your trip meter.

 

I always use the miles remaining counter and it seems to work pretty good and is pretty useful down to about ten miles left. After that it just says Low and you better be looking for gas pretty quick. I think the most I've ever put in mine is somewhere around 4 - 4.5.

 

When I bought my bike it had 2400 miles on it. Same problem as you speak of, then it plain crapped out. The dealer fixed it under warranty and even the tech said what these guys attest to. The gages suck.

 

Mine is accurate only when the tank is totally full, and bone dry empty,,,I run off the trip meter as well, Next step is simply to get rid of it altogether.