fuel leaking into intake from needle, what to do?

Discussion in 'Mechanics Garage' started by iron_monkey, Mar 27, 2015.

  1. iron_monkey

    iron_monkey New Member

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    One of my carbs is dripping fuel from the needle outlet down the intake and into the engine whenever the fuel pump is on. It made my engine hydrolock!

    The seal between the needle and the main jet (the gold thingo that the needle slides into) is not great or something. The engine will start nevertheless.


    Im at my wits end. How the heck do i fix this? Its not the float valve, it shuts the fuel when the float is up. I doubt it is stuck, i can move the float up and down and feel no resistance. The needle/black vacuum assembly slides freely.

    Replace the jet or whatever that golden thingo is called? This is not the first problem, this thing leaked fuel from the fuel rail so I had to painstakingly disassemble the carb and replace the o ring. Now this! This carb assembly is a lemon.
     
  2. TOE CUTTER

    TOE CUTTER Mullet Man

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    The problem is in the bottom of the carb assembly, the needle in the slide that you can see down the bore of the carb has no ability to seal but is there to meter fuel as needed. The needle and seat in the bottom of the carb control the fuel level and flow onto the carb as it is consumed and when stuck will over flow the carb and cause the problem as described. You will need to remove the carb assembly (complete) and remove the bowl and inspect the needle and seat. Part #2 in this horrible picture.

    http://www.bikebandit.com/oem-parts/1986-honda-interceptor-700-vfr700f2/o/m151672#sch44476
     
  3. iron_monkey

    iron_monkey New Member

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    I have already done this. I moved the float up and down. When the float is up, it stops the fuel from coming as expected.

    That something else is causing this is baffling.
     
  4. squirrelman

    squirrelman Member

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    A rusty fuel tank can shed flakes that hold the float needles partially open.
     
  5. iron_monkey

    iron_monkey New Member

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    problem solved its the float needle.

    Yesterday afternoon I wasn't able to see the very subtle flow of fuel, this morning i can.


    I really have no idea whats wrong with it, as far as i can tell it looks exactly the same as the normally functioning float needles.
     
  6. NormK

    NormK New Member

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    Firstly check to see if you have bent a conrod on the cylinder that hydrolocked and then fit a fuel solonoid valve to the thing so it doesn't happen again. If you haven't damaged the conrod, consider yourself bloody lucky. Get a solonoid valve for under $20, never rely on float needles to shut the fuel off
     
  7. iron_monkey

    iron_monkey New Member

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    The hydrolock occurred when the engine was off, its not like it stopped running because of the hydrolock. I found out when the battery was having trouble starting the engine, and then within moments it couldn't turn over.

    Unless the starter motor fitted to a very small <1kg jumper battery is enough to bend a conrod.....
     
  8. NormK

    NormK New Member

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    Hydrolocks always happen when the motor is off, otherwise it wouldn't hydrolock. Plenty of rods have been bent when this happens, in particular if the piston is at the bottom of the stroke and has a bit of speed up before it hits TDC
     
  9. iron_monkey

    iron_monkey New Member

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    Err no, hydro locks commonly occur when fording a river/flood thats too high and the momentum of the live engine meets water...
     
  10. NormK

    NormK New Member

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    Ok good luck
     
  11. iron_monkey

    iron_monkey New Member

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    After googling looks like it is a possibility (in the context of car and plane engines), although hopefully with these short stroke highly strung motorbike engines its very unlikely.

    Even if the rod is slightly bent i would care less if it loses some hp. This engine is already way overpowered for the go kart im putting it in.

    Hopefully wont affect engine longevity/emissions/fuel consumption too much. Will find out in due course..
     
  12. jethro911

    jethro911 Member

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    Well now that you know that the float needle and seat aren't doing their job properly, it's a simple out with the old and in with the new proposition. If you inspect the old parts with a magnifying glass you may be able to see wear or corrosion on the needle or seat which would explain the leakage. I would suggest that you look closely at the other three while you are in there.

    Fingers crossed that you didn't bend a rod along the way. I've seen at least a half dozen bent rods (on snowmobiles) this winter due to failed float needles so I would say that you have a 50/50 shot but you won't know till you fire the engine and hear the bad noises coming from within.
     
  13. NormK

    NormK New Member

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    I find it funny that a bent rod is only going to cause a slight loss of hp
     
  14. iron_monkey

    iron_monkey New Member

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    Doesnt matter if this thing only outputs 50hp.


    Anyway started it up, nothing different from what i heard before. Smooth running. Looks like ive been lucky.
     
  15. NormK

    NormK New Member

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    Now you are just one happy little camper, so before you hurt yourself with this thing I would remove 2 spark plug leads :smile-new:
     
  16. iron_monkey

    iron_monkey New Member

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    Actually it really has stuffed the conrod, i just found out the cylinder is not combusting at all. The exhaust is barely warm. The spark plug is definitely sparking.

    Oh well :(. Now I have to find a way to stick the float up for the relevant carb to stop the dead cylinder from using fuel.
     
  17. NormK

    NormK New Member

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    What you could do is grind the intake valve lobes off the cam and this would prevent the valve from opening and sucking in fuel
     
  18. squirrelman

    squirrelman Member

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    I'm certain you could find a bolt that threads into the float needle seat threads to stop fuel flow.
     
  19. NormK

    NormK New Member

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    squirrel I thought my idea was better, but I didn't mention to him that he would need to do the same to the opposite cylinder so that it would run like a V twin and he should also take the plugs out of the 2 non working cylinders to take some load off the motor and the bent rod
     
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