Fuel coming out the gas cap

Discussion in 'Motorbike Technical Discussion' started by Masospaghetti, Jan 10, 2006.

  1. I filled up my Kz700's gas tank the other day to about 4/5 - there was
    still some room left. I was riding for about 5 minutes when I noticed
    gasoline was running down the sides of the tank and it was coming out
    the cap! What could cause this?
    Masospaghetti, Jan 10, 2006
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  2. Even if the cap was grossly leaking - how would it be pushed out the
    top? ( a new cap is like $80...gah)
    Masospaghetti, Jan 11, 2006
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  3. Masospaghetti

    oskar Guest

    Some gas caps have vents. If the gas tank is overfilled, the cap would
    leak gas out the vent hole.

    But later models would have unvented caps. You should check to see if
    your machine had an evaporative control system that used an unvented

    Check the parts diagrams on www.partsfish.com to see if your machine
    had a charcoal canister.

    During the mid-1980's, evaporative control systems were added to many

    If your machine had an evaporative control system, it would have a
    charcoal canister and some hoses going from the gas tank to the
    canister and a hose with at least one anti-backfire check valve
    connected to the carburetor. Fumes would be stored in the charcoal
    canister until the engine was started and then the fumes would be
    sucked into the engine when it was started.

    Look on the back side of the side cover for a decal that shows how to
    hook up all the evaporative control system hoses. Kawasaki color coded
    the hoses with different colored tape and the decal has dots of those
    colors to show where the hoses went.
    oskar, Jan 11, 2006

  4. A leaking filler cap, duh....
    chateau.murray, Jan 11, 2006
  5. And this would cause gas to be pushed out the top of the tank?
    Masospaghetti, Jan 11, 2006
  6. Thanks for the reply.

    I think the california model had a canister but my model does not. It
    does have the anti-backfire check valve though.
    Masospaghetti, Jan 11, 2006
  7. If it's leaking, it's leaking..... ;-)
    The Older Gentleman, Jan 11, 2006
  8. Masospaghetti

    John Johnson Guest

    If everyone's on the same page, please accept my apologies; however:

    It seems like Masospaghetti wants to know _why_ the gas is coming out of
    the top of his tank, perhaps as a simple inquiry, perhaps as a means of
    determining whether the gas cap is truly at fault.

    If it's the second reason, I'd think that the leaking gas cap is a
    problem that needs correcting irrespective of its "true" cause. If
    there's another problem, the gas will overflow out of the vent hose
    (it's still there, right?) instead of all over your tank. This is
    preferred for several reasons. ;-)

    I'd say, replace the relevant bits of the gas cap (dunno whether it was
    suggested to replace the gasket only, or the entire cap) first, then see
    if the problem recurs. If so, get back to us.

    Let me know if I've gotten anything wrong, and happy riding.


    'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.
    John Johnson, Jan 12, 2006
  9. Masospaghetti

    MadDogR75 Guest

    Gasoline expands when warmed. The gas in the
    Underground tank is at about 50 F. On a hot day it
    can expand a surprising amount.
    I had this happen once, touring on an old Honda with a
    center mounted filler cap.
    Gasoline on your scrotum fells cold at first.
    Then there is a uncomfortably strong impression of heat......
    Wakes you right up!
    Rode FAST to the next rest stop...

    MadDogR75, Jan 18, 2006
  10. Masospaghetti

    MadDogR75 Guest

    Check for wasp larva in the overflow hose.
    They tend to leave them there if the bike is stored out-doors.
    MadDogR75, Jan 18, 2006
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