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Yamah 2 cyl won't idle

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  • #1

    Yamah 2 cyl won't idle

    I bought the engine new in 2009.

    Stored my 15-MSH (15-horse twin), on its side, the side with the fuel strainer, for four months. After starting, it died and I found a lot of rain water and sludge in the fuel so the engine got a good dose of it.

    Cleaned plugs. Replaced in-line fuel strainer and cleaned the one on the engine. Drained carb bowl and sprayed lots of carb cleaner inside and let it sit before pumping up fresh gas.

    The engine starts but I have to repeatedly crank the throttle to keep it going. Even at high revs, it begins to die but I can save it by quickly working the choke out and back in immediately. If I get it going I can race around but it makes for some interesting landings at the dock.

    Adjusting the idle screw won't help. Is there some kind of cold-start system that might be stuck? Any other ideas out there?

    Many thanks,
    Stranded Bry...
    Tags: msh-15
  • #2
    I suspect that the carburetor and integral fuel pump need to be completely dismantled for a thorough cleaning. There are some incredibly small passages within the carburetor that might be clogged. Just removing the float bowl will not get them clean. I find a heated ultrasonic cleaner is sometimes needed.

    Have you thought about letting a Yamaha mechanic clean the carburetor for you? There is an access issue to the idle mixture screw that needs to be addressed. He will know how.

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    • #3
      Thanks Boscoe...

      I'm on a sailboat down island and no mechanics around. If I can't fix it myself, I'm in trouble.

      What do you suggest? I'm pretty good with mechanics, just not sure about outboards.... should I take the carb off and soak it in something? See if I can order a re-build kit?

      I'm really stuck right now and anything you can suggest would be much appreciated.

      Again, thanks,
      Bry

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      • #4
        If it were me I would remove the carburetor and fully dismantle it. Soak it as best you can in a good carburetor cleaner. Use a soft piece of copper wire to rod out the passages. The use spray carburetor cleaner to blow through all of the holes and passages to verify that they are free and clear.

        There is a plug that blocks access to the idle mixture screw. If your motor is a USA model. Carefully drill a hole in the middle of the plug without letting the drill bit go through the plug and damage the screw behind the plug. Then take a spare screw and thread it into the hole you just drilled into the plug. Grab the screw with a pair of pliers and pull the plug out. You can then unscrew and remove the idle mixture screw.

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        • #5
          Plus 1 ^^.

          You still have a bunch of junk in the carb, especially the main jet.

          Besides removing and cleaning, make sure you can see light thru the jets. As noted, the orifices are very small and it doesn't take much to clog them...

          And count the # of turns it takes to turn the idle air screw INWARD, so you know what to set it at when re-assembling...
          Last edited by TownsendsFJR1300; 02-27-2017, 07:42 PM.
          Scott
          1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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          • #6
            Thanks for the good info, guys. I'll do the best I can and get back to you with my results.

            Nice to have you both in my corner.

            Cheers,
            Bry

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            • #7
              Since you're on a sailboat and maybe this outboard spends a lot of time inactive learn to drain the gas out of the float chamber before any extended lay-ups to help prevent this again.....there is a small screw there on the float chamber for draining....and be sure to put a rag under it when you remove it so when/if you drop it the screw doesn't disappear somewhere.

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              • #8
                Good news, guys... a soaking in carb cleaner... six hours... did the trick. Idle is a little rough but it doesn't stall out and may improve with a few high-speed runs with the fresh gas.

                And yeah... that little drain screw is not only hard to remove, but randy too!

                Thanks to all of you I don;t have to hitch a ride to get a cold beer this evening.

                All best,
                Bry

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                • #9
                  Excellent!!

                  You may want to run some Yamaha RingFree thru the engine. It'll clean up and crap you may have missed and should help...
                  Scott
                  1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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                  • #10
                    Not too sure any high speed runs are going to fix the idle passages, but, strange things happen....might be time to pull the carb to bits and actually clean it, as advised, rather than "soak" it?

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