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  1. #1
    CB750 Member bigj750's Avatar
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    78k overflowing out of #1 carb

    I just took off my carbs to fix my accelerator pump. Got it to work finally but as soon as I put everything back on the carb overflowed. I took off the carb inspected the float/float height everything seems fine and also replaced the needle. Again it overflowed like Niagara out #1 carb what am I doing wrong?? It's never done this until I took the carb off to check the pump.


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  2. #2
    CB750 Guru amc49's Avatar
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    Disturbed settled sediment in the carb inlet from moving it around.

  3. #3
    CB750 Member bigj750's Avatar
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    Quote Originally Posted by amc49 View Post
    Disturbed settled sediment in the carb inlet from moving it around.
    Carb inlet being where at specifically?


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  4. #4
    CB750 Guru amc49's Avatar
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    The entire pathway from petcock to the needle seat can be called that. Didn't think the idea was that hard to understand. Anywhere in there with a horizontal running component to form a shelf sediment can settle on. Move carb around, it stirs up and then runs into needle seat to block it open. If they use ethanol in your local fuel the particles can be so small they go right past any plastic filter Honda might use there, the pores being too big.

    The problem not unusual, I've seen it personally more than once.

  5. #5
    CB750 Member bigj750's Avatar
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    Quote Originally Posted by amc49 View Post
    The entire pathway from petcock to the needle seat can be called that. Didn't think the idea was that hard to understand. Anywhere in there with a horizontal running component to form a shelf sediment can settle on. Move carb around, it stirs up and then runs into needle seat to block it open. If they use ethanol in your local fuel the particles can be so small they go right past any plastic filter Honda might use there, the pores being too big.
    Sorry been working on the damn thing all day I'll have to clean out underneath thag seat and yes. I'm Chicago area all gas stations have ethanol. Any gas additive to counter balance that?


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  6. #6
    CB750 Guru amc49's Avatar
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    Nope, none at all. They say it will but it doesn't work.

    Cars don't have much issue unless the evap system is leaking to vent it. Bikes though can have issues if you use fresh fuel and let the bike sit 2 weeks, then float issues show up. The carbs are way too open to the atmosphere and the ethanol then soaks water right up.

    Ethanol is pretty transparent if the vehicle drives every day to keep fresh fuel in it, it's when the vehicle sits the problems really begin, a bike driven like once a week or so will soon show trouble.

    I have fits with it in my CB550, paper fuel filter used in it catches the rust but the resistance of it can create fuel issues if I run the tank dry, it's slow to prime when refilled.

  7. #7
    CB750 Member bigj750's Avatar
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    Quote Originally Posted by amc49 View Post
    Nope, none at all. They say it will but it doesn't work.

    Cars don't have much issue unless the evap system is leaking to vent it. Bikes though can have issues if you use fresh fuel and let the bike sit 2 weeks, then float issues show up. The carbs are way too open to the atmosphere and the ethanol then soaks water right up.

    Ethanol is pretty transparent if the vehicle drives every day to keep fresh fuel in it, it's when the vehicle sits the problems really begin, a bike driven like once a week or so will soon show trouble.

    I have fits with it in my CB550, paper fuel filter used in it catches the rust but the resistance of it can create fuel issues if I run the tank dry, it's slow to prime when refilled.
    Right it's tough to find out here. Cleaned the inlet and everything works, guess I had to fully understand how the float and needles work together. Sometimes it's the simplest things that fix it.


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