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2016 Yamaha 4hp/4 stroke carb and fuel issue

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  • 2016 Yamaha 4hp/4 stroke carb and fuel issue

    Little less than a year ago, I purchased this new Yam 4/4 and used it to upgrade from 6 year old 2.5 Suzuki 4 stroke. I often switch back and forth using both of them on a Solo Skiff. I always flush after use and turn gas valve into off position to allow gas in carb to burn out so no gas left in carb. I store on a motor stand inside a shop.

    I let it sit for about a month in August, when I took it out to test run it prior to fishing, I tried to fill internal gas tank (only about 1/3 full). Gas poured out of top and all over engine. Strainer in mouth of fill was somehow clogged and would not let gas through. I removed strainer, careful inspection showed no debris, foreign matter...looked normal. I had to dump gas from strainer then use compressed air to clear , took several tries, but finally allowed gas to pass through.

    While strainer was out, checked for water/debris in bottom of tank... nothing. Re-inserted strainer and filled tank.

    I then tried to start motor, no start, nothing.. After checking fire (spark good but plug was dry) and drained a little fuel from carb bowl, it looked fine, I took to dealer. He called me back to say carb was clogged with dried water residue and minor debris from "lack of use and improper fuel"..... I use non-eth, fresh gas, same tank as I use to fill Suzuki 2.5 (it starts 2/3 pull every time)..... Estimated cost to repair - parts and labor $300/$400.... carb rebuild or possibly new carb.... does this sound right? I checked fuel in 3 gal tank and no water or residue...????

    I have two other Yamahas, both 50 hp 4 strokes, one 17 years old, one I bought new in late 2015.... I am a Yamaha guy... but this just sounds weird? what could have clogged strainer it was not in fuel fuel level was way below it...

    ANY insight would be appreciated...

  • #2
    Best to drain each carb with float chamber drain screw.....removes any water/debris/etc. "Running motor dry" by turning off fuel doesn't really remove all fuel/water/debris....leaves some in bottom of float chamber to dry out/gum up, etc...


    • #3
      ok, but why? Suzuki 2.5 fires 3rd pull, same gas, same storage, same everything.......I have the cheapest Troybilt power washer sitting right beside it... gas stays in it for months at the time... use it about every 3/4 months... cranks 3rd/4th pull.... and what's the story with clogged strainer? Still cant figure out why it was clogged... or what clogged it. I should not have to baby a 10 month old motor like this to keep carb from clogging up after sitting only 3/4 weeks! One guy told me to make sure I run it 10/15 minutes EVERY week!? Then dealer says running it on flush not good enough, need to run it at high RPM in the river....


      • #4
        if there is no sign of water in the gas can but there was in the motor tank then it must be from condensation.
        Keep as much air out of the tank as possible by keeping it full and watch where it is stored.
        Running a motor til it dies does not remove all of the fuel out of the carb.
        I prefer to keep the carb bowl full and run often, or drain the bowl completely for long storage times


        • #5
          The why is because motors today are made to run as lean as possible. So lean that almost anything will clog them up.

          I suspect my Poulan chain saw and your Yam F4 carburetor might have been made by the same folks. Let the chain saw sit a month with gasoline in it and it is a bear to start.

          One solution to your carburetor may be to use a larger jet size. Or to ask your dealer to leave the idle mixture screw cap out so that you can fiddle with the idle mixture.

          But before you do anything either have your dealer call, or you call, Yamaha to ask for goodwill to get the carburetor fixed. They know all about the problem you are having.


          • #6
            Thanks for the replies and espec boscoe99, yes I had a similar problem with my 2000 Yam 4 stroke, but fixed it with a 10 micron filter. This little motor, no way to involve a filter... the strainer clogging still baffles me... condensation coating it?..... but wouldn't gas pouring through sort of flush the condensation?.... 2 stroke motors (chainsaws) all have the oil mix thing to deal with... as far as calling Yamaha and dealer, did that first thing, they're working on it... interesting to see how it works out.... considered pulling the carb myself, but was worried about voiding warranty....also thought about changing the carb around to convert to 6 hp..(say they're having less trouble with 6hp). then I read somewhere THAT's illegal.... really? If you bore out a motor, doesn't that essentially change the hp? ... people do it in cars, motorcycles, OB motors all the time...? Anybody have insight on that?


            • #7
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              You have a greater chance of getting a speeding ticket than you do of getting a ticket for fixing your carburetor so that it runs well.

              I take my chances with speeding tickets and take my chances with fixing my own motors. On both of my chain saws I purchased a tool to adjust the carburetor. A carburetor that has a screw so that it can't be adjusted.

              A Yam dealer is not going to risk his livelihood by making a necessary carburetor adjustment. A good independent mechanic might just do it.

              If the motor is going to sit I would try 99Yams suggestion of draining all of the fuel via the carb float bowl drain. Costs nothing but a bit of time and might work for you.

              Good luck.