fueltank Interpreting Fuel Tank Capacity

[suppresst]

I searched the other dirt bike forums and could not find a definitive answer the question I pose below, so I'm trying this technical forum -

When the manufacturer states in "specifications" for a particular bike that the bike has, say, a "Fuel Tank Capacity" of 2.0 u.s. gallons, and the separately states that the "Fuel Reserve Amount" is .50 u.s. gallons does that mean the .50 reserve is additional to the 2.0 gallon tank capacity, or that the reserve is a component of the 2.0 gallons?

 

[William1]

Normally, it means total capacity from a dry tank is 2 gallons. Of that you have a half a gallon of reserve, which means your main primary amount is 1.5 gallons. However, there is a few ounces at the bottom of the tank you rarely can use so total usable amount is a touch less than 2 gallons. On some machines, they measure every drop of fuel the bake can take and therefore even include the fuel lines and carb float bowl!

Similarly, when the weigh many bikes, it is dry.No fuel, oil or even water in the radiator. Though that is changing and they are calling it 'wet' weight.

[suppresst]

 

12 minutes ago, William1 said:

Normally, it means total capacity from a dry tank is 2 gallons. Of that you have a half a gallon of reserve, which means your main primary amount is 1.5 gallons. However, there is a few ounces at the bottom of the tank you rarely can use so total usable amount is a touch less than 2 gallons. On some machines, they measure every drop of fuel the bake can take and therefore even include the fuel lines and carb float bowl!

 

Now on another forum this website titled "Revisiting fuel tank capacity" (or a title close to that) many of the contributors had made various experiments with their tanks with some disturbing results. Most disturbing (although this was not an "experiment") was a rider who's rated tank capacity was 2.0 gallons but the bike would always run dry after 1.0 gallon. This issue is critical to me since I usually ride alone and in remote places. Do you know, is that particular story a fluke, and do most factory tanks drain true to specifications?

[William1]

10 hours ago, suppresst said:

 

Now on another forum this website titled "Revisiting fuel tank capacity" (or a title close to that) many of the contributors had made various experiments with their tanks with some disturbing results. Most disturbing (although this was not an "experiment") was a rider who's rated tank capacity was 2.0 gallons but the bike would always run dry after 1.0 gallon. This issue is critical to me since I usually ride alone and in remote places. Do you know, is that particular story a fluke, and do most factory tanks drain true to specifications?

Most excessive 'measuring' of capacity is with a bone dry machine and filling it until the fuel level is at the very top of the filler neck. Obviously, no consumer ever has a dry bike and never fills to the lip of the filler neck. When on reserve, and the bike 'runs out of gas', there is still some fuel in the tank, some in the carb, just not accessible in the tank and too little in the carb for the engine to run.

Fuel tank design plays a critical role in this too. Some are like 'saddlebags' and a significant amount of fuel can remain on the side opposite the petcock. To access this 'extra' fuel, you have to lean the bike over, possibly several times during a ride to get all the fuel to the petcock. Some bikes solve this with a crossover line.

Also, some people do exaggerate. I suggest, if you know your bikes worst case consumption rate, to drain your fuel tank via the petcock, then measure how much can be put back in to fill to a normal 'full' amount.

FYI, when I go for a ride, I never include reserve as part of my distance calculations. Reserve is for an emergency.

[Chuck.]

On a new bike I always check tank capacity and gas mileage, I hate hiking in riding boots.

I fill the tank using 1 quart containers with the valve on reserve and watch for gas flowing out of the petcock, then top off the tank.  You can also repeat by draining the tank via the petcock to verify when you need to switch to reserve.

I then do several rides to calculate gas mileage, and reduce that by 10% for trip planning.

On one bike I can see the stand pipe from the fill and use that to gauge how much gas is in the tank. On some other bikes I have added a gas level sight tube using clear gas line connected to the line to the carb and routed up the front edge of the tank to upper triple clamp, I then mark the front of the tank in 1/4 gallon increments.