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Carb & Fuel Flow Question

Discussion in 'Gas Engines' started by Bartman, Jun 3, 2019.

  1. Bartman

    Bartman Defender of the Noob!

    Hi all,

    Today is the day to finally start the ZDZ RV 80 that came on the hundy buck Cap 232 that I basically adopted last winter.

    Here's the thing, with the choke closed it sucked up fuel into the line almost immediately but when I stopped flipping the prop, the fuel ran back into the tank. Is that normal?

    The carb is a Bing 49.

  2. Snoopy1

    Snoopy1 640cc Uber Pimp

    The bing carb is very similar to the walbro. It also has 2 flapper check valves on the pump side. One of them prevents the fuel from running back to the tank. So I believe you need a carb kit to correct the problem.
  3. Bartman

    Bartman Defender of the Noob!

    Now that the engine and carb are good and wet the fuel isn't running back anymore but I'm stuck with the ZDZ/Bing problem now where it runs a second or two and dies. Doing the 5-5-1 method which works to get it running but it won't stay running.
    Last edited: Jun 3, 2019
  4. Snoopy1

    Snoopy1 640cc Uber Pimp

    Please explain the 5-5-1 method.
  5. Bartman

    Bartman Defender of the Noob!

    5 flips of the prop, full throttle, choke closed, ignition off
    5 flips, full throttle, choke open, ignition off
    flip until it starts with choke open, idle throttle, ignition on

    it works, engine starts right up but then dies. pump diaphragm doesn't have a hole in it but it's not tight so I suspect that that is the problem. pump doesn't do anything when choke is closed, right?

    Played with high and low needle settings, not much difference with anything in particular. Parts for the Bing 49 aren't available so I ordered a cheap rebuild kit that looked similar just to see what the diaphragm looks like when it's new.

    Might order a new Walbro carb, not sure at this point.

    By the way, @TonyHallo , i came across your name today in some very old engine posts. You've been around the block a few times I see! :)
    49dimes likes this.

  6. 49dimes

    49dimes Damn I'm hungry

    I would use a new carb. Walbro HDA248A will work well with 60-80cc engines. The reason I state this is... replacing the diaphragm and pump side gaskets does not always work as you have found out. Sounds like you have a restriction internally or even a faulty check valve. When I say check valve I mean the internal check valve just ahead of the HS jet. Not the pump leaflets built into the pump side gasket.

    I have seen them go for about 50 bucks.
  7. Bartman

    Bartman Defender of the Noob!

    Thanks for the help so far guys. The go to carb back in the day was the Walbro WJ-71 which then became the WJ-71-1 which was then discontinued........but........according to Walbro email customer service, it is still sold as a Husqvarna carb, made by Walbro.

    @49dimes I'm not a carb expert but the carb looked spotless inside when I opened it up this afternoon, not a bit of stuff in the screen, not a spec of build up anywhere in the carb. BUt if I can't get parts, I can't get parts.

    Is this the one you're talking about dimes? $261!! yikes
  8. 49dimes

    49dimes Damn I'm hungry

    No. That price is insanely ridiculous. Some knob will buy it though lol.

    Sorry Bart I meant the HDA246A. Mile high has it for 51$ and in stock. He says 60-70cc engines but it will do just fine on the ZDZ 80 single.
  9. Bartman

    Bartman Defender of the Noob!

    OK, thanks for the correction, will be traveling for a few days so will pick this up when I get back.
  10. 49dimes

    49dimes Damn I'm hungry

    Ok. Have safe travel.
    Bartman likes this.

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