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321 will not stay running...(non-cooling issue)

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  • 321 will not stay running...(non-cooling issue)

    My 321 will not stay running to save my life..... Runs great for about 10 seconds and then starts bogging down popping and eventually shutting down. I have tapped the block to be able to run mikuni fuel pump for marathon. I checked reeds to make sure they are not crack or lifted. Any help would be appreciated. Haven't dug into real deep yet.... it cost me some much needed points yesterday.

  • #2

    Re: 321 will not stay running...(non-cooling issue)

    We had a problem this weekend at Yelm with our 321 on the runabout. We warmed it up on the cart, then during race time it would not start.........When it did get going, it would bog after about 10 seconds....

    Comment


    • #3

      Re: 321 will not stay running...(non-cooling issue)

      My guess is it runs with the prop out of the water just fine. The minute the prop hits the water, blah.

      If this is the case, your head gasket is blown.

      It's easy to check. Remove the 8 nuts on the head and take a look. If you haven't done this before, the head gasket is about a 30 thousandths aluminum.
      You're simply looking for a break in the webbing of the gasket. If it's broke, obviously replace gasket and re-torque the nuts to 17-20 pounds in the pattern shown in the Yamato owners' manual. If it happens repeatedly the actual head might by warped but that doesn't usually occur.

      Tim
      Tim Weber

      Comment


      • dpracer95
        dpracer95 commented
        Editing a comment
        Tim I didn't have time last night to check out the head gasket.

        It does do exactly that. (Dies when it is set into the water to take off) However. It will not stay running when I dry fire on land.....

    • #4

      Re: 321 will not stay running...(non-cooling issue)

      Check the gaskets on the fuel pump installation,could be sucking air instead of fuel.

      Comment


      • Matt Dagostino
        Matt Dagostino commented
        Editing a comment
        No fuel pumps on Stock Yamato's. But perhaps Doug put clear fuel line on it so you can see if their is a fuel blockage? Also take the float assembly apart and clean it out. Hope you and the kids are all well. Matt

    • #5

      Re: 321 will not stay running...(non-cooling issue)

      Yes, I know no stock fuel pumps,but he said he tapped the block for one,though maybe he installed it.

      Comment


      • #6

        Re: 321 will not stay running...(non-cooling issue)

        Have you checked the fuel cap to ensure the air valve is clear (no blockage)? Other potential, besides head gasket or carb float valve, is that your intake manifold is loose or its gasket is damaged (the intake manifold on my 302 got loose during a race and motor died out - sucking too much air)... quick fix with a 10mm wrench (memo to me - check torque on all bolts prior to race).

        Comment


        • #7

          Re: 321 will not stay running...(non-cooling issue)

          When I first got my 321 there was no fuel coming out of the tank. There was a mesh filter covering the hole in the bottom of the tank not letting any fuel through. I ripped the mesh out and it fixed the problem
          Matt Dagostino likes this.

          Comment


          • #8

            Re: 321 will not stay running...(non-cooling issue)

            Update: checked head gasket- no cracks or breaks of any kind.

            Float needle was about 3/8 of an inch off from what it should have been. Adjusted it to 31mm (1 1/4")

            Checked spark- PLENTY

            After about 5 pulls fuel is dripping from exhaust about every 10 seconds.

            It's a new motor. Wth is going on!?

            Comment


            • #9

              Re: 321 will not stay running...(non-cooling issue)

              New update: Turned gas off rolled it over until cylinders cleaned out. Put new plugs in it. Rolled it over until it fired. Once fired turned gas back on. Never bogged or sputtered or anything. Now I'll find out if it stays running in water. Very confused though.

              Thanks for all the input and advice.... Matt we will see you this weekend hopefully in Alexandria.

              -Dustin

              Comment


              • #10

                Re: 321 will not stay running...(non-cooling issue)

                My guess is it is a carb issue. New motor means it was in storage a good while. Shellacing of fuel residue is common. The screen in the fuel tank should be removed and the carb disassembled and cleaned. Don't overlook the richner valve as you do this. Should fix your problem.

                Comment


                • #11

                  Re: 321 will not stay running...(non-cooling issue)

                  Are you using the stock gravity feed tank, or a remote tank with a fuel pump?

                  When I got my 302 I disassembled the powerhead to drill and tap for a fuel pump. I never could get a simple system fuel pump to work. Too much fuel pressure was blowing the needle off the seat. I never invested in return hoses, pressure regulators...I had my stock tank extended.

                  I would recommend using the stock tank to get it dialed in first, then work on the fuel pump and remote tank.
                  sigpic

                  Comment


                  • GrandpaRacer
                    GrandpaRacer commented
                    Editing a comment
                    With out the return path and associated pressure regulator the fuel pump will cause a real rich mixture. I bet Mike got it right here!
                    john
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