I'm having problems with my 02 F4i's fuel tank. I get about 80 miles before the reserve turns on and a full tank for me is around 2.2 gallons. The manual says the F4i gets abut 4.76 gallons. I'm at 16,000 miles on odometer and I just ordered some new NGK Iridium sparks to replace and I also have a K&N air filter. Just waiting for those spark plugs to come in to install it. I also have on a Yoshimura RS-3 and a PCIII mapped for the RS-3. From what I've read in other forums the sparks and air filter could be the solution to my horrible mpg problem but that still leaves the capacity problems. Anyone know why the manual says it can hold 4.76 gallons, yet I'm only filling up around 2.2-2.5 every fill up? Could it be a problem with the reserve indicator coming on too soon? I also think it could be a problem with my PCIII map. Of course I'm going to remap it when I install the air filter but that still leaves my capacity problem. I've ran down the reserve before and before I filled up, I checked the tank and it was literally empty. Can't figure what the problem is. Solutions to my horrible mpg would be appreciated too! Thanks!

 

When you fill-up, do you insert the nozzle into the tank, or do you fill it to the base of the tank opening? If it's the first, then you're not doing it right. Otherwise, you may have a faulty fuel reserve sensor. If that's the case, you can replace the fuel pump assembly, OR visually inspect the tank to determine fuel content. You can also re-set your trip-odometer and calculate fuel loss that way. Average range is like 120+ miles (to be safe).
Another thought is, like you mentioned, the PC. Do you smell a strong odor of unburnt fuel when stopped? Maybe try and unplug it & see how the bike runs without it. Bad fuel pressure regulators can also cause increased fuel consumption.

 

I had the same problem along with some others. I changed my fuel pressure regulator. It was a big help. It was still running really rich so I manually edited my pcIII to run leaner. If you read your directions on your pcIII it should tell you how to do it. Its really easy to do

 

If you can physically only fill the tank with 2.2 gallons than you aren't filling it up all the way OR not letting it run out far enough. Obviously your reserve light is F'ed up so you might not want to fill up just because it comes on.

I typically begin to think about swinging through the gas station at about 180 miles or so. NOT 80!!!!

 

I don't see how I'm not filling it up all the way. Yes, I am putting the nozzle into the tank, but it still fills up pretty high. I would be able to touch the gas if I stuck my finger in there. If anything, I have less than half a empty gallon floating on top. That still doesn't explain the other 2 missing gallons. How am I supposed to fill up at the base? I thought the nozzles were made so that they had to be pressed in to work. I'll try riding to 100 and checking inside again. I've ran it over 100 twice, where the entire reserve bar was blinking, and when I went to fill up, I couldn't notice any gas left inside. That or my eyes are bad. Also, my PCIII is set on lean but since I'm going to remap it with the air filter, I'll double check it again. I don't smell any odor either. Sparks are coming in Friday so I'll do everything this weekend and hopefully I can narrow down the problem. My guess is that the reserve light is messed up but I'm not sure which part is the problem. Is the reserve sensor part of the fuel pump assembly? I can't find it in the manual. Thanks.

 

When you open the gas cap, and look inside the hole, you'll see a thin metal bar that goes across the opening. You can fill it up to that point. If you over fill it, it'll just exit out the little hole on the side, and out the overfill tube. When putting fuel in, just hold the nozzle in the filler neck, but not quite inside the tank. As the gasoline level reaches near the base of the filler neck, let off on the trigger so the fuel is not coming out at full blast, and top it off slowly. A full tank will have visible gasoline about 3/4" from the brim.
As for the Fuel Reserve Sensor, it does appear to be part of the fuel pump. The diagnostic procedure is in section 19-17.

 

If you are only getting 80 miles on a fill up and your fill up is 2.2 gallons, then that is 36 mpg. That is not bad, it is not great either, I get around 43, but I don't ride hard and keep under 6k generally.

Sounds like the problem is you are not filling up. The shape of the tank is such that it doesn't hold much at the bottom, and alot at the top like funnel.

 

You should be able to fill up to 3.1 or so when the reserve bars light up. Faulty sensor my guess. It's happened a few times on the forum... although rare.

 

Ignore the ****ing reserve light - it is OBVIOUSLY incorrect if you are getting 80 miles on 2.2 gallons it is coming on WAY too early. Like was said you are getting 36+ miles per gallon.

Consequently you could go 144 and only have burned 4.0 gallons, leaving roughly a half a gallon in the tank. You just simply are only buring half your tank because the light is faulty.

 

but you are missing the part where he said theres really no gas visible in the tank after the reserve goes off. Id myself would rather not going empty backroading or in town.. that could do some damage.