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I have a Honda Varadero 2010. When I fill her up to max, the level of the liquid in the tank is at maximum, just a tiny bit below the rim of the nozzle. Then, I poor in some more and the level raises up to the nozzle but afterwards it drops again just to the original maximum!

So I repeated this exercise a few times and the tank seems to be made of rubber. I put in about ten such "additions" and each time with the same effect. (Then, I realized that it might be bad for my beauty so I stopped.) There's no leakage or anything and the bottom of the bike is as dry as my bank account at the end of the month.

What is all that about? Does Honda make a magical, bottomless bikes?!

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    Just to experiment, you could see if it has something to do with the pump operation by filling up from a jerry-can next time. If the level in your tank keeps going higher this way, then you know the pump was doing something weird.
    – ALAN WARD
    Jul 16, 2015 at 18:50
  • What is "jerry-can"?
    – Konrad Viltersten
    Jul 16, 2015 at 19:20
  • I mean an auxiliary fuel tank with a handle that is used to transport fuel outside vehicles. Many desert expedition vehicles have them on roof-racks both to transport fuel and water (separately, of course). Basically, I just mean to fill up the tank from another recipient, not a station fuel pump.
    – ALAN WARD
    Jul 16, 2015 at 19:24
  • Oh, I though you referred to the fuel injection pump. Now I get it - and I've already tried that. It's consistent at a number of stations so either they're inflicted with the same malfunction or it's something with how the fuel is being taken into my bike. Like if there's a chamber that it pumps into for later or something...
    – Konrad Viltersten
    Jul 16, 2015 at 19:27
  • I don't know if your bike has only a side stand or only a centre stand but I know from experience that if I sit on my bike and keep it upright then I can get an extra litre or two in.
    – Mauro
    Jul 17, 2015 at 10:42

2 Answers 2

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The extra fuel will be being distributed into the breather system of the fuel tank. Most fuel tank have the main fill tube which the fuel goes into plus at least one additional smaller tube to prevent air becoming trapped in the tank. It is likely that you are filling the fill tube with fuel which is then being forced into the tank and up into the breather tube so that the level in the fill tube appears to drop.

@t.Q. is correct in his assertion that the nozzle at the pump has it's own return tube too and it is not good practice to fill up after the pump has cut out at it's maximum level more than once because an amount of the fuel you are forcing into the filler tube of the tank will be being pushed back into the fuel pumps overflow.

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The extra gas you are pumping in your tank is likely going back into the pump at the station, which is also drying out your bank account!

Most gas stations are equipped with vapor recovery systems that feed the gas back into their tanks to prevent vapors from escaping into the air, which would otherwise contribute to air pollution.

Also, according to the U.S Environmental Protection Agency:

If you top off your tank, the extra gas may evaporate into your vehicle’s vapor collection system. That system may become fouled and will not work properly causing your vehicle to run poorly and have high gas emissions.

For theses reasons, it is in your best interest to ease off the trigger when you hear that first click at the nozzle.

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  • It's not really vaporizing as the volume of liquid is quite a few cubic centimeters and the drop takes only two, three seconds. Also, the drop then stops as it reaches the (intended) maximum level. Also, I'm poring the fuel from a height of an inch or two (because the vapor detector click it off otherwise). More suggestions? +1 for links.
    – Konrad Viltersten
    Jul 16, 2015 at 19:19
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    It not only collects vapours but the extra fuel as well.
    – tqrecords
    Jul 16, 2015 at 19:39
  • @KonradViltersten - I assume Sweden is even more environmentally conscious than is the States. What t.Q. is saying is spot on, as I bet your country has the same type of collection system. The nozzle is designed to pull back vapor, but will also suck up as much excess fluid as it can to help prevent a spill. Your best bet is to follow the instructions given above and just fill your bike up to the top, where the handle clicks once, then don't try to add anymore.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Jul 16, 2015 at 22:31

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