- This topic has 7 replies, 7 voices, and was last updated 15 years, 9 months ago by AaronMerlot.
Filling up the gas tank too full?
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July 7, 2008 at 2:13 pm #1688BoredHRParticipant
New to the board, so if this has been asked before, my apologies. Just bought a 2006 Honday Shadow VLX (600), and prior to taking off the lot, the dealer’s tech took me through a basic intro to the bike – here’s the brakes, throttle, choke, etc. When running through refueling, the tech stated that I should not fill the fuel tank to capacity – when the pump does the auto-shut off, I shouldn’t top off – because the “excess” fuel will seep through the system and into the charcoal canister.
Huh?
Thanks for any feedback.
July 7, 2008 at 2:27 pm #8483megaspazParticipantWell I don’t know about the auto shutoff thing, but you should poke your head and look at the levels when you’re pumping. You don’t want to overfill because when the bike gets hot the gasoline can expand and overflow. On my tank, there’s a fill line which is basically the bottom of the length of the hole where the gas pump goes in.
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If there’s anything more important than my ego
around, I want it caught and shot now…July 7, 2008 at 2:58 pm #8488shagglesParticipantThat’s good to know because I’ve been filling my tank right up to the cap. I guess I should stop doing that.
July 7, 2008 at 3:05 pm #8489ShannonGParticipantMy owner’s manual said something about not overfilling your tank. I think spaz is right.
July 7, 2008 at 6:40 pm #8514JirikiParticipantyeah, spaz is right… check if there is a line…
that being said, it is physically impossible for me to overfill my tank, because i fill it when it is leaned over (on the kickstand )… fuel gauge never reads above 7/8s once it is righted again…
July 7, 2008 at 7:12 pm #8517RabParticipantYes, that’s dead right, you should only fill to the bottom of the filler neck.
In a gravity fed fuel system (on a bike with carburetors), there’s a gas tank “breather” hole at the top of the gas tank near the gas cap. The breather hole is connected to a breather tube which goes down to the bottom of the engine area. The purpose of the breather is to let air into the gas tank as the gas level drops through use. If it didn’t, a vacuum would be created in the gas tank and the gas would no longer gravity feed into the carburetor(s).
These breather tubes used to just vent to the open air, however, since clean air regulations came into effect, the “open-end” now plugs into a charcoal cannister, which is supposed to catch any gas which is in the *fumes* coming out of the breather tube. I.e. it allows air into the breather from outside, but filters any air drifting out of the gas tank when the bike is not running.
If you over-fill your gas tank (bike on side-stand), when you straighten the bike up to ride away, you could slosh gas down the breather tube, thus soaking the charcoal cannister. Once soaked, it cannot pass air and therefore a vacuum will form in the gas tank. After a short while, you’ll experience the symptoms of running out of gas.
If this happens, you’ll be able to tell, as when you open the gas cap, you’ll hear the air being sucked-in (and the bike would then run for a short while until a vacuum formed again).
One thing you could do if it happens to you is to pull the breather tube off of the charcoal cannister (probably under/behind the engine) and leave it off for a while to dry out; you should immediately be able to re-start the bike. Be absolutely sure it’s the breather tube and charcoal cannister you’re disconnecting! Once dry, remember to put the tube back on again.
DO *NOT* DISCONNECT THE *GAS* LINE FROM THE GAS TANK, PETCOCK OR CARBURETOR.
Alternatively, I guess you could ride with the gas cap a little loose to let air in (not recommended).
It happened to me a few times before it was explained to me what was happening, and the first time, I got the bike trailered home ($150+) as I didn’t know what was going on except that the bike wouldn’t re-start.
Hopefully, having read this, this won’t happen to you…
Disclaimer: This is given as advice only. You are responsible for ensuring your own safety.
July 7, 2008 at 7:21 pm #8519BoredHRParticipantThat sounds like what the Honda tech was talking about.
July 8, 2008 at 4:48 am #8556AaronMerlotParticipantThis spring I filled the tank as high as I could get it (gas was cheap that day). After a 10 minute ride and sitting in the sun for another 10 minutes gas started to flow out a small tube under the frame of the bike. I totally panicked and called the dealer asap. After a couple of questions he new exactly what I did and told me not to worry and burn off as much gas off as I could on the next ride, and to leave at least a 1/4 inch gap between the gas and the filler tube in the tank just below the cap. It also said it in the manual. How I missed that I dunno.
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