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Solved GSXR 250 GJ72A Carbs Flooding - Solved

Discussion in 'Suzuki 250cc In-line 4's' started by Andrew Niles, Feb 5, 2018.

  1. Andrew Niles

    Andrew Niles Active Member

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    Hi Guys.

    Have been struggling with this one for a while, so looking for some advice on a path to move forward.

    Am rebuilding the above bike, and have got to the stage where it will run very nicely but the carbs continuously flood. If I have the bike running and connect the fuel tank (without manually controlling the flow of fuel) it will eventually flood the carbs (to the point where fuel can be seen coming out of the vents at the front (air intake side) of the carbs. This will happen as well if I connect the fuel up without the engine running.

    Suspected it was the floats and/or the valves. So pulled carbs apart and replaced the valve and its assembly. No difference. Have even tried going completely stupid with the float (i.e. having it set very high) and this still didn't prevent the problem.

    Confirm that floats are free to move once assembled (took out drain and checked movement).

    Not sure what else could be the problem. Once the fuel gets to (about) the correct level the bike runs well, so the other settings (Idle screws) would appear to be set somewhere near about right.

    Did find (initially) that one of the chock valves and spring was missing (replaced) which was causing some problems, but now just need to work out why these %%$^^$& carbs wont stop flooding.

    Any suggests of what else to check or other possible causes would be most appreciated.

    Cheers

    AJ
     
  2. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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  3. Andrew Niles

    Andrew Niles Active Member

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  4. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Please describe how the float needles are fitted to the floats and how you set the float levels. Do you have easy access to the carbs and bowls? Perhaps you could remove all 4 bowls, hold the floats up with a rubber band or similar and then use a remote fuel tank to supply fuel. If none of them leak then put a bowl on number 1 carb and repeat, until you find which one is leaking. Some carbs have pinholes in the casting this method will help you find that too.
    Does this model have a fuel pump?
     
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  5. Andrew Niles

    Andrew Niles Active Member

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    Hi Maelstrom

    Firstly the float needles (shown in GreyImports post) are fitted to the tang of the float by sliding onto the tang using the wire loop so that they are suspended when inserting. There are only two bowls (each carb services two cylinders) and have tested that they do indeed shut off fuel when held in the position that they should be. Both bowls appear to be flooding when fuel is connected.

    My suspicions as they are right now is that both floats are 'jamming' (as in stopping moving as apposed to playing music :) ) and this is occurring once they have opened, hence not shutting off as they should.

    I am planning on fitting an external pipe so I can monitor both fuel bowl levels to see more clearly what is happening.

    Fuel is gravity feed from the tank, with a vacuum valve to allow fuel to flow when the bike is running (has a prime setting to bypass this if required) and have confirmed this functions as I expect it to.
     
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  6. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Did you replace the float seat's too ?
    If not sometime's the oring's can dry out allowing fuel to go into the bowl's still

    Also are the 2 vent hose's clear and not blocked, they aren't joined from one pair of carby's to the other are they ?

    [​IMG]
     
    Last edited: Feb 5, 2018
  7. Andrew Niles

    Andrew Niles Active Member

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    gsx250f_carbs.PNG
    Yes replaced the seat as well, but reused the old o ring. Tested that there was no leaking from around it though, but might run another test on that to make sure.

    Thinking I might replace the bowl seal as well as that hasn't been changed out.

    Hmm which ones are the vent hoses. I suspect they are connected together. Would this cause the problem? Is this them that I have marked?
     
    Last edited: Feb 5, 2018
  8. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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  9. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    definately new o rings on the seat ..... put a liitle rubber grease on them before install
     
  10. Andrew Niles

    Andrew Niles Active Member

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    Yes, nothing really wants to stop it. Can drain a lot of fuel relatively fast too. :(
     
  11. Andrew Niles

    Andrew Niles Active Member

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    Yeap just about to order them.
     
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  12. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Yea pull off the vent hoses and see if fuel comes out there ... looks like the ones u have marked
     
  13. Andrew Niles

    Andrew Niles Active Member

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    Will give them a good clean out as well. Cheers might be just the thing.

    Having had a good look at the diagram and thinking about it, I think this is likely the problem, that with the vent hoses joined (that was how they were when I purchased the bike - though it had only run once apparently), the build up in pressure as the bowl fills will be enough to eventually push fuel out through the other outlets causing the apparent flooding, and stopping the floats from reaching the level to actually shut off the fuel.

    Does that make sense?
     
    Last edited: Feb 5, 2018
  14. Andrew Niles

    Andrew Niles Active Member

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    Solved by My67xr. Someone (previous re-builder) had fitted a hose between the two vents on either set of carbs. As soon as i removed this, bike runs, idles nicely, and revs out too. Great effort. Thanks team, appreciate all the help and feedback.

    Cheers

    Andrew
     
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