Am I going crazy? Why wont my fuel flow enough to the carb?

Discussion in 'Motorized Bicycle General Discussion' started by nidyanazo, Jul 16, 2010.

  1. nidyanazo

    nidyanazo New Member

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    I must be losing my mind. Here's the situ.

    Turn petcock off. Pull the fuel line off carb. So now one end is connected to the petcock and the other is in your hand. Put a catch bottle down and open the petcock valve to make the fuel flow. It comes out fine. Now I shut it off.

    Re attach the line to carberettor and turn the petcock valve to open. The fuel barley drips out.
    WTF. My motor is not getting enough fuel. I can see the level drop down as I give it gas, and slooowly raise back up. This is prob. something retarded, but what could be causing this anomaly?

    Makes no sense at all. Pull the line back off and fuel comes out just fine. But it back on and hardly anything. :-||

    I'm just going to stick an inline 3psi pump on there to ensure constant flow if we cant collectively solve this one!! Help me out guys! :)
     
  2. Goat Herder

    Goat Herder Gutter Rider

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    Once a blue moon on a hard run my Morini would die out of no where, but start right back up. I was going to adjust the float but never did. It started behaving. I would take a close look at the carby got trash in it some how? Do that first before messing with the float. Are we talking Morini or China? Still suggest the same get a closer look at the carb. With the float bowl bottom cover off it should flow very well when working the float.

    Tank could be building a vacuum too . Might not have enough venting at the fuel cap.

    I had a cheesy pet cock from a china kit kept getting trash in it and clogging. The tank filter gave away. That one annoyed me. I could not find a replacement petcock as messing with it I gave up on it looked like a bad part waiting to happen at the time.

    My china kit has a swamp cooler shut off valve at the tank. [The little valve that ties onto the outside house water spigot.] That thing can't get clogged much larger of an opining in it's pathway . Never leaked never clogged I use a inline filter further down stream with it for the carb.
     

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    #2 Goat Herder, Jul 16, 2010
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  3. Goat Herder

    Goat Herder Gutter Rider

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    Here's another question. Does this happen all the time or when the motor is hot?
     
  4. nidyanazo

    nidyanazo New Member

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    all the time (just started)
     
  5. Goat Herder

    Goat Herder Gutter Rider

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    Just one fleck of debree of any kind in the carb's fuel gallery will do it. If'n you are methodical about it gently disassemble it down to the bare carb. Then go after it with compressed air and brake clean or something similar. With the carb put together you can reattach the fuel line with the float bowl off. VERY gently work the float and valve you should be able to see flow there. Last the float bowl should possible need the tangs very gently adjusted.

    Adjusting the float bowl can be a bit of trial and error.
     
  6. camlifter

    camlifter Active Member

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    when a china motor does that you can push the tickler to lower the float and let fuel start flowing. what hapens is if the float bowl is full there can be an air bubble in the fuel line and fuel won't flow untill the carb uses some gas and the floats drop down. just pull the line off the carb and let the line fill up before putting it back on the carb, this usually happens after you've run out of gas or drained the tank and refilled it.
     
  7. halfevil333

    halfevil333 New Member

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    ...sounds to me like your fuel line is getting pinched some how when you bring it back toward the carb! this was happening to me until I ran the line to the outside of the frame, rather than between it...
    and also, ditch the filter that came with your kit and get one for a lawnmower w/a paper filter in the clear plastic bowl! fuel will flow MUCH BETTER!!!!
     
  8. 2door

    2door Moderator
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    In the original question your concerns seem to be with what you see in the fuel line and not how the engine is running. Are you having engine problems or simply assuming that the engine is starving due to a partially filled line? There is a lot of misconception regarding the flow required for a small single cylinder 2 stroke engine. Some will tell you that you must have a gusher coming from the fuel tank. Not so. You want a steady flow, not dripping but any steady flow will feed the engine sufficiently. Pay no attention to what you see in the fuel line or transparent filter that you might have. You'll see all kinds of levels and flow depending on several factors such as ambient temperature, throttle position, float level, ability of the tank to vent, etc. Confirm that the tank/cap is venting properly and don't worry about the visual indications.
    Also forget any ideas about adding a fuel pump. Any added positive pressure will only force the needle valve open and flood the engine. They are designed for gravity flow only. The float can not apply enough upward force to counteract the pressure of a pump.
    Tom
     
    #8 2door, Jul 16, 2010
    Last edited: Jul 16, 2010
  9. nidyanazo

    nidyanazo New Member

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    Thanks guys, I swapped the fuel tubing and went with a different tank cap and everything's fine now. Still getting air bubbles in the fuel line while riding hard, bu I know as long as the float bowl is full things are good.

    Appreciate the help, will write back if the problem acts up again. Ordering a new experimental tank now so we'll see if that changes things (larger petcock and opening)
     
  10. halfevil333

    halfevil333 New Member

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    I agree however I know that when the fuel line went between my top bar and the lower accent lines, it was getting pinched, and def' starving her for fuel @top speeds, I now have it to the outsid with a better filter and I've been whizzin through the rush hour traffic ever since!
     

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  11. broHSI

    broHSI New Member

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    You have your fuel filter on backwards.
     
  12. 2door

    2door Moderator
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    The man is right. Flip the filter over. If there is an arrow on it, it indicates the direction of flow. It does not mean, "this end up".
    Tom
     
  13. momentummotorgroup

    momentummotorgroup New Member

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    i had the same problem on one of my builds. turned out there was a pinhole leak in the jug gasket that was negating suction for the fuel to pull through. Switched out petcock, fuel filters, cleaned the carb, etc, and in the end it was just a pinhole leak screwing everything up.
     

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