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  1. #11
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    There are so many things that can be causing a bog here. Off the top of my head...maybe others can chime in too:

    1. Have you checked compression?
    2. Did you check the popoff pressure with the needle and seats on your carbs to be sure they're not leaking?
    3. Did you confirm that the fuel lines are routed correctly?
    4. Did you confirm that the fuel pump diaphragms and check valves are not creased?
    5. Did you check the water separator doesn't have any water in it?
    6. Did you confirm the fuel restrictor is in place on your fuel return line?
    7. Did you check to see if there is an air leak on your fuel selector valve?
    8. Did you check to be sure both check valves on the fuel tank are installed correctly and are not clogged?
    9. Have you tried clipping 1/4" off the end of your spark plug wires to be sure you're getting good spark?
    10. Could you please confirm the jetting and screw settings you're using? (I've gotten the LS and HS screws backwards in my head before)
    11. Have you checked that the carbs are all sync'ed up correctly?

  2. #12

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    First, thank you again for your help!
    1. Yes, even within a few lbs 130 on my gauge.
    2. Yes
    3. Yes
    4. I made sure pump diaphragms did not leak I did not pull pumps apart, did blow through. What do you mean by Check valves? Also verified diaphragm on other sides of carbs in good shape.
    5. Yes and tried bypassing.
    6.yes
    7. Yes and tried bypassing
    8. Two valves? I thought only one on vent? I did try removing cap.
    9. No, but I will.
    10. 82.5 pilot, 180/175/180 mains, low 1 3/8 high 0
    11. Yes

  3. #13
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    For the popoff, what readings were you getting? I presumed you checked each carb individually and got 15-18 psi and it held the pressure after it popped?

    There are two small circular check valves in each fuel pump that can become creased. Check the parts diagram and you'll see what I'm talking about.

    The fuel tank has two check valves: one to let air in so it doesn't go into vacuum when you burn fuel and one to keep a couple psi of pressure in the tank. The vacuum check valve is a disc looking valve that should be easy to blow through one way but you can't the other way. The pressure check valve is really a relief valve that should pop at a couple of psi. You'll need a mighty vac or some sort of 5 psi air pressure to see when it pops open. You won't be able to blow through it which is why you need the mighty vac or air source.

  4. #14

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    I don’t have a pressure gauge only a vacuum gauge so to test popoff I regulated my air compressor to 15 lbs plugged return and blew in fuel in all carbs connected none popped. Then raised to 20 lbs and they did so figured close enough. I can borrow an actual tester and try again if not? Do I need to do individually if all hold until 15-18lbs then after?

  5. #15

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    Iíll look into the fuel pump but wouldnít it run out wide open not accelerating in that case?

    For the tank valves does it need slight pressure in the tank to run correct? I guess I didnít realize two valves only the one that lets air in when fuel used.

  6. #16
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    That really isn't the best way to check popoff. You'll never know if you have a leaky N&S valve or one that is so far out of spec.

    The tank has some pressure to help with fuel delivery. If either one of those valves are not operating correctly, you could have issues. There is a single vent connection on the tank that has a line that goes towards the steering helm. There will be a tee connection in the vent hose that has the vacuum check valve and the pressure relief valve usually is connected to a rubber grommet fitting on the helm under the hood.

  7. #17

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    I will check the pop off properly, check the vent valve and clip some off plug wires tonight. I was thinking on the pop off if testing together if they pop and hold you are good but I get it now that won’t tell if one needs too much pressure to pop, but that seems unlikely. It should tell you that none are leaking though?

  8. #18
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    I'd say check the vent/check valves and clip the wires first and go from there.

    By using a regulator from an air compressor, you won't really know if they are leaking since the regulator will open up to keep the pressure once the N&S pops. That is why it is preferred to use a pump with a guage so that you can slowly pressure it up, see where it pops, and see that it hold the remaining pressure after the needle reseats.

    A leaky N&S will for sure show up as a rich bog since you'll just be dumping unmetered fuel into the carbs.


  9. #19

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    Pop off tester I was going to borrow is broken so I ordered one and will have to wait for that. Plug wires seemed fine but I cut them back. Fuel vent only has 1 valve no t and it’s the one that lets air in but not fuel out.

  10. #20
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    I'm not going to say that the fuel system valves are going to be 100% critical on your system but I know for sure they help a lot.

    Were you able to do any testing after clipping the wires?
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