(5.75 gallons to the drilled holes!)
OK, so to possibly put this baby to rest while keeping this info for posterity, here's what I finally came up with.
I'd run the tank onto reserve and put 15 miles on it before pulling the tank off the bike.
I drained ALL THE FUEL into a measured bottle. I leaned the tank to the left side at times but kept it level while the fuel drained out, just to see how much it would actually flow into the carb
if it was still hooked up.
It drained ALL OF IT. Virtually every last drop!
So after 15 miles running on reserve I still drained a full 10 cups of fuel (2.25 qts., or 5/8ths of a gallon).
Assuming I'm averaging 46+ MPG I could safely predict that I had another 23 miles before nearly running dry, and that would still leave 2 cups of fuel in the tank. That means 38 TOTAL miles on reserve, and likely 40+ iffy miles on level ground at highway speeds.
Adding that to the 25 miles I ran after the fuel light came on and before switching to reserve and I have a pretty solid 60+ miles from when my fuel light comes on (though I'd rely more on the reserve tank than the fuel light).
Good to know!! I'll know that I have a really safe 25-30 miles after hitting reserve.
So what I did next was to put 1 quart back into the tank and run it down to the local Chevron which is about 1/2 mile from my home. From there I added OVER 5.5 gallons of gas! I posted a pic below.
That gives me a total fuel capacity of just about 5.75 gallons to the center of the holes I drilled in the filler neck. So the 5.3 gallon capacity touted by Yamaha is likely to the bottom of the filler neck, as someone stated earlier. We averaged just over 46 MPG on our last 491 mile measurement. If we use that as an average while riding 2-up we could run 265 miles before running totally on fumes.
I think I can now extend our 'must reach' range scenario to 240 miles if in a crunch or even just for kicks, especially if we keep it under 75. We ran around 2/3's of our last trip between 80-90 MPH at altitude, much of it uphill, which challenged our fuel mileage a bit.
So now we can put this to rest and file it away for personal future reference, until I get a new, larger diameter, rear tire LOL. But knowing that I have 5.75 gallons on a stuffed fuel tank and that it'll run itself virtually DRY is great to know.
Regarding running dry, I had a single quart when I ran it to the gas station, my better half on standby waiting by her cell phone, with a way-too-long wait at a stoplight along the way. Now think about that. It means that I can AT LEAST run out 5.5 gallons on the road.
But here's why it'll run even more than the 5.5 gallons. When you go around left hand corners the fuel runs into the reserve petcock, supplying the fuel pump (if you still have one) and everything beyond. That fills the fuel line, fuel pump, and carb float bowl. You may run around a right hand corner that temporarily robs the petcock of fuel, so the bike continues to run on what's below the tank in the lines and carb. Straighten up or hit a left hand turn, or lean the bike to the left at a stop light (which I did on the way to the gas station), and it again feeds the beast below. It should keep doing that until you're completely dry.
This may be one true advantage of having the fuel pump vs. relying on gravity feed. The fuel pump will suck faster when fuel is available and keep everything pressurized beyond it until more comes down the tube.
Do I ever suggest that anyone runs dry? Of course not. But if you run up against that remote country gas station that unexpectedly closed at 5 PM (or on SUNDAY as many do in Utah and elsewhere), you may find yourself assessing whether you should turn around and go back to the station you passed 25 miles earlier or move ahead to the larger city that's 40 miles down the road. If my fuel light just came on but I haven't yet switched to reserve then I may well confidently head to that station ahead rather than retrace my route. I know that I have at least 60 miles when the light comes on, and around 40 when I have to switch to reserve.
I HATE backtracking! So boring...
Then again, we have AAA towing as a backup (hehehe).
Safe riding everyone!! Hope this helps for a future ride or tight squeeze scenario...
The tank will hold 5.75 gallons when stuffed to the rim of the fuel cap opening.