Hydrolocking....!

Discussion in '1st & 2nd Generation 1983-1989' started by blairmac, Aug 19, 2020.

  1. blairmac

    blairmac New Member

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    Afternoon Gents...

    My '86 VFR 750: Cylinder # 3 insists on filling with gas.. I've change all the float needles and seats and reinstalled; still filled with gas. Pulled carbs again and checked/adjusted the float bowl height on #3 and reinstalled. Still leaking gas into the cylinder, but doesn't seem to be getting into the crank case (I've changed the oil twice just in case).

    Is there anything I'm missing? Any other way that gas can get in there that I need to check?

    Thx
    Blair
     
  2. sixdog

    sixdog Member

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    Your float needle could be defective ... the thing with the rubber end on it .


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  3. sixdog

    sixdog Member

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    Switch the needle to another carb and see if that cylinder fills with gas ... also make sure your float is ok ... no holes etc


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  4. blairmac

    blairmac New Member

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    Thx sixdog - float needles are new; and I checked the float by submersing it in water (no bubbles) before re-installing it. Float didn't seem to be binding or hanging up at all, and I set the tab to close the needle a bit more aggressively (?) last time. I could switch needles with another carb to verify it's good, but seems suspicious that the same cylinder keeps locking up. Was wondering if there was any other way gas could be leaking past the float bowl or somehow through the carb to get into the cylinder?
     
  5. sixdog

    sixdog Member

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    If I am not mistaken the only way fuel gets into the float bowl in through that needle ... unless the the o ring or crush washer on the valve assembly is missing or damaged .... hmmm


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  6. blairmac

    blairmac New Member

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    By valve assembly do you mean the float valve seat and filter cup? Will check when it all comes out tomorrow... again
     
  7. sixdog

    sixdog Member

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    Yea that thing ... :)


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  8. squirrelman

    squirrelman Member

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    u got the alloy washer under the float needle seat and seat is tight ?
     
  9. blairmac

    blairmac New Member

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    Thx Squirrelman - Yep... pulled carbs last night. Washer is there, seat assembly was nice and snug. Should I try swapping the floats and needles between the rear carbs to see what happens?
     
  10. straycat

    straycat Member

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    You should be able to air test the needles & seats.

    put a piece of clean fuel line on the carb fuel inlet barb and blow through it, then while blowing, move the floats to closed position to seat the needles (with 4 of them you may need to tape 3 of them in the closed position while you manually test the trouble one).

    Make sure you manually move the float to the correct angle/adjustment per the book to tell if its actually seating the needle. if it is you wont be able to blow though that fuel line any more. If the float requires more movement than specified in the manual to close the needle/seat you will have to adjust the tab on the float.

    As someone else suggested if you remove the floats, you should also be able to tell if there is fuel inside any of them causing them to malfunction and not close the needle/seat. I see you checked for bubbles, so I assume you checked that they didnt have fuel in them.
     
    Last edited: Aug 21, 2020
  11. TimK_PA

    TimK_PA New Member

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    I recommend bench testing carbs and doing straycat's method to check for leaks. Bench testing usually finds the simple problems before taking the time to actually install the carbs.

    Just use wood scraps to get the carbs in the same orientation as mounted on the engine and hook up a fuel supply. Leaks usually appear in seconds once the bowls fill...
     
  12. Dannoxyz

    Dannoxyz New Member

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    TWO things have to go wrong for this to happen.

    1st petcock not shutting off fuel when engine stopped AND
    2nd as you're looking into, float-valve not sealing and cutting off fuel-flow

    Petcock has priority since if it's working properly, NO FUEL should flow at all when engine's stopped, regardless of float-valves' conditions.
     
  13. Diving Pete

    Diving Pete Member

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    My petcock leaked even in the off position...

    You 'may' need new float valves - however polishing the valve seat with a Q tip & ultrasonic the valves does work & is what I'd do next.
     
  14. Dannoxyz

    Dannoxyz New Member

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    Yes, petcock is bad.
     
  15. Diving Pete

    Diving Pete Member

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    also as stray cat has said BENCH TEST..

    Unless you have Honda Genuine valves & seats then the polishing is almost a requirement
     
  16. Diving Pete

    Diving Pete Member

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    If the petcock turns off the fuel with no leaks - then its only one side thats may be able to be rebuilt - thats a bench test with a sheet of A4 paper underneath for a couple of hrs (overnight is good) ...

    You can bench test the carbs with all the float covers removed. Do this outside - lol, position the carbs so they are level, remove all the covers & attach a fuel bottle.
    Note:
    You will spill fuel...
    Be ready to stop the fuel supply.
    The floats SHOULD not allow any fuel to flow as they will be hanging in their normal CLOSED position. The ones that leak need attention / polishing..
     
  17. Captain 80s

    Captain 80s Member

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    I don't see a petcock that doesn't completely stop the flow of fuel in the "off" position as the problem. The fuel would have to then go down hill, overcome the fuel pump and then go back up hill to the carbs. And then have enough pressure to overcome a float valve. And those viton tipped float valves can withstand true gravity feed pressures no problem.

    Bench testing the floats and valves with a gravity feed bottle has to be your next step.
     
  18. BoomerDave

    BoomerDave New Member

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    This might be belt and suspenders but I like to put an inline fuel filter AND manual fuel cutoff valve in the lower end of the fuel line, just before it goes into the carbs. I don't trust petcocks.
     
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