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Suzuki DT65 -88 - Difficult engine problem

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  • Suzuki DT65 -88 - Difficult engine problem

    Hello! As a last resort for im asking you all here for help.

    I have a Suzuki DT65 -88 that wont rev/run properly. However, it starts very easy. To get it to rev at all (in gear) I must put some choke on. Therefore I assume its a carburator problem (lack of fuel). There is an airscrew or whatever its called and its now screwed in on max (moore fuel) (runs worse if u screw it out). I got no tachometer so I cant really tell you how much I can rev but I would say max 4000 rpm. The top speed is 21 knots with my Jofa 485, it should easily do 30-35 knots.

    -The cylindertemp sensor (for warning) is unplugged
    -The throttle sensor is unplugged (if I had this plugged in the engine would stop after exactly 15 seconds every time)
    -The VRO is disconnected including the sensors

    Things that has been done so far:
    -Cleaned carburators very strictly. Everything looks very good and Ive even done this twice. One time even with an ultrasound-cleaner.
    -The reeds are new
    -Fuel pump is new including hoses
    -Tried with another fuel tank and hoses to it, made no difference
    -Cylinder compression is good

    I dont have the indicators or anything for the warning system on the engine, however ive bridged the cables that was suppose to go to the reset button. How can I say if the engine is limiting the rev to 3000 rpm? Does it sound like running on the revlimiter on cars?

    The engine temperatur have also been measured manually and it was all good.

    Im running out of ideas....Thanks in advance!!

    Its also consuming ALOT of fuel. about 1,7-1,8 liters per nautical mile.
    Another really odd thing was that it went even worse at first (top speed 6 knots). But then I fueled up with 98-octane fuel (less ethanol) and some sort of fuel system cleaner. Then it went ALOT better after a while, but not good of course. I find this so strange when I know for certain that the carburators look fine.

  • #2
    You may have introduced other problems but that motor won't run properly without the throttle sensor hooked up and properly adjusted. It's only running for 15sec because the cdi advances the timing for that long on a cold start.

    Comment


    • #3
      Sealfie, it does sound like you have a bad throttle sensor, but like mphelle8vld said you may have caused more problems disconnecting so much.

      The air mixture screw on the carbs is for idle, and needs to be set per manual (all carbs set through same).

      It is still possible you have a fuel problem if using ethanol fuels for long time. Ethanol causes fuel lines, and fuel pumps to deteriorate, and may block small pas-sages or needle valves, or jets (high speed, low speed).

      How are you mixing oil and gas now? Do you use a good additive in every tank?

      Post back when able. Good luck.

      Comment


      • #4
        Thanks for the reply Solarman!!

        We have 2 gasoline types in Sweden, its 95-octane E10 (=10% ethanol) and 98-octane (with less then 5% ethanol). Shouldnt be a problem and ive checked and /or replaced all fuel lines/hoses. The reason I wanted to go with 98-octane was so that I would get less oxygen in the fuel (since ethanol has 30% oxygen in it)

        With the air mixture screw set 1,5 out (like it should) i need to choke moore to get the revs up but it runs better on idle.

        HOWEVER, after spent over 100 hours searching for the problem I discovered today that one of the cables to the gear counting coil is disconnected/cut. The cables were well hidden...I will connect the TPS and the cable to the gear counting coil and see how it works out.

        By the way, if this doesnt work, how do I test the TPS?

        Edit: Im premixing in the fuel tank. 2-2,5% 2-stroke oil. No moore additive is usually needed but the additive I put in was some kind of fuel system cleaner and it went alot better after that. One mechanic said that it could be a coincidence so I dont know.
        Last edited by Sealfie; 08-26-2016, 08:32 AM.

        Comment


        • #5
          If ethanol fuel is used, you should always use an additive, ethanol fuels can change to almost water (phase change), if it gets slightly old.

          If, you did not use compressed air to blow through all air, fuel pas-sages, and all jets in carbs, there may still be particles lodged in those areas. Also, the manufacturer on some motors used different size jets in some multiple carb motors, to balance fuel flow in those motors. Do not mixup those jets between carbs.

          The gear count coil, pulse coils (magneto) and TPS control timing on that motor. They must be operating properly.

          Your pre-mix should be 50:1 mix. For example 50ltrs fuel With 1ltr oil, or in USA 50 gals fuel with 1gal oil.

          Good luck, post back how it's going.
          Last edited by Solarman; 08-26-2016, 10:39 AM.

          Comment


          • #6
            Originally posted by Solarman View Post
            If ethanol fuel is used, you should always use an additive, ethanol fuels can change to almost water (phase change), if it gets slightly old.

            If, you did not use compressed air to blow through all air, fuel pas-sages, and all jets in carbs, there may still be particles lodged in those areas. Also, the manufacturer on some motors used different size jets in some multiple carb motors, to balance fuel flow in those motors. Do not mixup those jets between carbs.

            The gear count coil, pulse coils (magneto) and TPS control timing on that motor. They must be operating properly.

            Your pre-mix should be 50:1 mix. For example 50ltrs fuel With 1ltr oil, or in USA 50 gals fuel with 1gal oil.

            Good luck, post back how it's going.
            Okey. thanks for the info!

            I did what I said I was gonna do and it runs great now!!!! 30 knots according to GPS, very good acceleration and muuuuuch better fuel consumption!

            The thing is that the engine is actually totally renovated. However they couldnt figure out what the problem was (they were, like me at first, 100% sure it was a fuel problem) so they mounted another engine on their boat when their patience ran out. And now around 1,5 year later I bought it from him (a friend) for around 500 dollars, it even has working powertrim so i couldnt resist. When they connected the electrics they forgot to plug in 1 cable from the gear counter coil, that was the hole issue. The cables were really hidden though and I finally found the issue looking at a wiring diagram following basically every cable from CDI.

            Comment


            • #7
              Am glad you found the problem.

              Enjoy your boat, happy motoring.

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