2006 Hyosung GT250R


Leaking lots of petrol when engine is on


Hasn't been ridden in about 10 months.

Has been stored outside with cover, leaning on it's stand.

I've started her twice in the last 2 months and every time it leaks.

Had been fully serviced and roadworthy 12 months ago by a mechanic.


15 second video of it leaking on it's second start today




I've done some reading that this is either a breather or overflow for the fuel tank, and I can accept that.

I just want to know what my course of action is. Leave it leaking till it stops or go for a ride and let it sort itself out?

  • 1
    That isn't a leak, it's a flood! Do not ride that bike until you get this fixed. I wouldn't even run the bike again until you get it fixed. It's just an accident waiting to happen. Is the bike fuel injected or carbureted? Commented Oct 24, 2015 at 12:57
  • It's fuel injected. It's worrisome that the rubber tube is leaking onto the hot exhaust pipes too.
    – Ari
    Commented Oct 24, 2015 at 14:06
  • The problem can most likely be found between the fuel pump and the injectors. It could also be either the fuel regulator or in the return line, if so equipped. I don't have specific knowledge of this bike's configuration, so leaving this as a comment of general knowledge to hopefully help you figure out the issue. Commented Oct 24, 2015 at 14:08
  • That is quite a bit of fuel. I didn't get any audio with the video. Is that what happens when you turn the key to the ON position? Commented Oct 26, 2015 at 23:02
  • Yeah. I start the bike up and that happens. While the bike is off it doesn't leak. I was bold enough to try again today but had the same result, it isn't showing any signs of slowing down the drainage.
    – Ari
    Commented Oct 27, 2015 at 4:11

3 Answers 3


I left it for another couple of months in a well ventilated area without riding, and lo and behold, it stopped leaking. Turned out that it may have been high fume/pressure in the fuel tank.

Thanks for the answers!

  • You may want to check your gas tank ventilation then. Your fuel tank should vent to the atmosphere. As well, if that pressure can overcome your float bowl needle and seat mechanism with it's pressure, that as well is a major issue. Best of luck. Cheers. Commented May 12, 2016 at 3:00
  • As well, thank you for coming back and answering the question. +1 for that alone. Very thoughtful of you. Commented May 12, 2016 at 3:01
  • I wish I had the means to have taken her to the mechanic at the time! I agree that it shouldn't have leaked so much. The only variables are temperature and pressure to cause the fuel to expand that dramatically. I will research your further advice.
    – Ari
    Commented May 12, 2016 at 3:10
  • It's entirely possible that your float needle and seats were the cause. If it happens again, take the wooden handle side of a hammer and tap the carbs repeatedly and see if it stops. If it does, it more than likely means that your float needle seated in the seat of the fuel delivery galley and is now functioning. You can then replace your needles and seats for a very low cost. Good luck! Commented May 12, 2016 at 3:12

I'd check the fuel lines for splits or leaks. In a fuel injected bike I wouldn't expect fuel to make it past the pump unless the ignition is on, and line attempting to pressurize

Regardless of cause, this is a disaster waiting to happen with fuel spilling over the exhaust headers. DO NOT RUN THE BIKE it's far too likely to catch fire, should it actually run at all.

  • I emailed my mechanic with the same content in this thread and he also speculated that it was a split tube. I intend on taking the bike to him (somehow) within a week for him to assess.
    – Ari
    Commented Oct 28, 2015 at 10:39
  • @fanuch any updates from the mechanic? would be nice to know how it turned out.
    – Leliel
    Commented Nov 26, 2015 at 21:48

Looks like the needle in the carby isnt resting in the seat properly due to debris in the fuel line, this will hold it open and allow fuel to flow freely, happened with my dirtbike sometimes you can just flush the debris out other times the seal in the seat has gone and needs replacing

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