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Gasoline leak - yamaha xj900 1983

Discussion in 'XJ Technical Chat' started by Andreas Novella Olsen, May 26, 2021.

  1. Andreas Novella Olsen

    Andreas Novella Olsen New Member

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    hello, i have a gasoline leak, cant figure out where its coming from. And how to fix the problem.

    its a yamaha xj 900 from 1983.
    i notice the gasoline smell when i was holding for red. when i got home and turned the bike off it was leaking like a "broken water hose" first i saw it came from the left side "carburetor cylinder head" it was weird, i took the tank half off then i saw it was from the middle were the "fuel hose" from the tank is connect to the carburetor then i took of the tank to do that the "fuel tap" needs to be ON (the fuel tap as always been ON) or RES to safely remove.

    now it comes to the part i dont understand, it was still leaking!! is there a problem in the "fuel tap"
    dont really understand the teknik in the "fuel tap" what it does, my options are "RPI, ON, RES"

    is it normal for the "fuel tap" to still be dripping and the "fuel hose" is just not connected correct on the carburetor..

    ---

    when the bike is this old, does the yamaha XJ900F fours '83 to '94 book from haynes work for my bike when its not an XJ900F or anything? just from 1983.
     
  2. Franz

    Franz Well-Known Member

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    You have a vaccum fuel tap assuming it's the Yamaha original. The fuel tap should not release fuel when on or at the reserve setting unless the engine is running. Prime is just to fill the float bowls. The fuel will run on prime with the engine off. You will need to rebuild your fuel tap.

    Where exactly was the fuel leaking from? It should not be on the cylinder head that's dangerous.

    The Haynes manual will be fine for your bike.
     
    Last edited: May 26, 2021
  3. Minimutly

    Minimutly Well-Known Member

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    Agree, get a petcock rebuild kit.
    On the leaking - the 900 should have vent pipes on the float chambers if I recal, and if the float valve needles or seats are passing, and the overflow/vent rubbers leaking it could be from here. Or, the fuel inlet tees rubbers or hose is leaking.
    You may have a rusty tank issue - causing the valves to stick open due to rusty bits, so worth a look in the tank.
     
    Jetfixer and Franz like this.
  4. Andreas Novella Olsen

    Andreas Novella Olsen New Member

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    Yes, there is a vaccum hose. i notice the leak first time near the cylinder head because the fuel hose is connected in the middle, dont know if the hose wasn't connect probably might be sense it was leaking.
     
  5. Andreas Novella Olsen

    Andreas Novella Olsen New Member

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    when i took the fuel tank off and the vacuum/fuel hose off it startet leaking from there.
     
  6. Franz

    Franz Well-Known Member

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    Yes the tap needs repaired.
     
  7. Jetfixer

    Jetfixer Well-Known Member

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    The PRI position fuel will flow , the ON position will only flow when there is a vacuum to the Petcock. If your float needles are not sealing fuel will flow and this can quickly fill the crankcase with fuel . The float needles will harden and get a groove on the rubber tip and won't seal properly. On one of my Seca's I have solid brass needles they are not cheap but think that is worth every penny. I would suggest pulling the carbs , drain float bowls , pull float bowls and remove float pin , pull floats and check needles see if tip is hard , it should be pliable . Agree fix petcock as well .
     

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