Ask MO Anything: Inaccurate Fuel Gauges

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By John Burns

Dear MOby,

I’ve owned three Japanese bikes since ’07: a Suzuki, a Honda, and a Yamaha. All three of them had the same annoying flaw in the fuel gauge. They all read full until half the gas is gone, then suddenly drop to half. From there on they give a fairly accurate readout for the rest of the tank.

I’ve asked around about this and some explanations I’ve heard are: “Americans like their gas gauges to work this way,” and “they do it that way so it seems like you’re getting better gas mileage than you really are.”

My theory is that it’s the best they can do given the small tank sizes that bikes have, or their unusual shapes, compared to the big, rectangular box shapes that most cars and trucks have.

What’s the real story?

Kenneth Moore

Dear Kenneth,

There are some things science still can’t explain, and this is one of them. Actually it’s perfectly simple. They all do that. But seriously, I was so impressed by the range indicator on our new Goldwing, I assumed there was some new electronic trickery that measured each atom of fuel as it passed through the throttle body. But when we look at the diagram we see that, nope, there’s part #25, the same old float on a stick vehicles have been using forever. The Honda‘s gauge looks full for a long time before it too drops to two bars.

In a motorcycle’s weird-shaped tank maybe even more than in a car’s usually simple rectangular one, part of the problem may be that the float can only go up so far, and most of us fill the tank all the way to the top of the filler neck even though all the stickers on the tank warn against it – so maybe that’s like …read more

Source:: Ask MO Anything: Inaccurate Fuel Gauges


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