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1995 Yamaha 70HP TLRT will not advance.

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  • 1995 Yamaha 70HP TLRT will not advance.


    The symptom:


    Cold engine throttles up and runs under load for a good while. Can and will power down and power backup with no stalling, sputtering, or otherwise noticeable problem. Once hot the unit will lose power even while on plane. When throttle is advanced “bogging down” symptoms get worse. Engine will stall unless put into idle then can be advanced again but only carefully. Whether or no it will get back on plane seems arbitrary. It did this for the better part of a year until finally now it will not advance at all under load. Now it sputters and stalls It will run continuously slightly above idle.

    Things I have done:
    1. New fuel line and squeeze bulb
    2. New water separator
    3. New Fuel pump
    4. Cleaned fuel filter
    5. Rebuilt Carbs
      1. Fuel was pooling around intakes and poured out when tilted.
        1. All new gaskets.
        2. New needles
        3. Adjusted floats
      2. Ran under load with top open to see fuel spray which looks good.
    6. Tested compression
      1. Plugs Fouled brown/black greasey
        1. Service Manual says bad spark.
    7. Tested Ignition coils.
    8. Reseated Caps
    9. New Plugs
      1. Properly Gapped.
    10. Tested Crank Position Sensor
    11. Testing CDI

    I am mostly convinced something is CAPUT in the CDI. I think this because of the progressive dying, temperature factor to failure, and exhausting fuel issues.

    Any Thoughts?


  • #2
    Why not follow the ignition system testing procedure in service manual if you think the spark is a problem.
    measuring peak voltages into and out of the CDI wil tell if there is a problem with those

    Comment


    • #3
      I am but everywhere I look everything says the CDI either works or it doesn't with very very few people claiming that is not the case.

      Comment


      • #4
        You can test CDI for proper operation, believe me I got fooled with the notion they work or not before. The fine gentlemen on here set me straight on that...I ended it up with a spare CDI.

        Do you have Yamaha manual?


        Do you have a decent multimeter?

        You will need one of these to go with your meter.

        https://www.amazon.com/dp/B00R3B6HYW...detail_1?psc=1

        Comment


        • #5
          I do have the service manual. I have a shit analog meter and a boss digital one. The manual says to use analog when measuring the CDI for some reason. Going to try both and see what I get. The manual didn't say anything about peak voltage, what is that about?

          Comment


          • #6
            Follow the procedures in manual
            good inputs but bad out puts loaded and unloaded means bad CDI
            bad inputs loaded and unloaded points to the stuff under the flywheel or wiring

            google cdi troubleshooting guide and read up

            Comment


            • #7
              http://www.cdielectronics.com

              Will have a chart with specs.

              Comment


              • #8
                Originally posted by cclemens View Post
                I do have the service manual. I have a shit analog meter and a boss digital one. The manual says to use analog when measuring the CDI for some reason. Going to try both and see what I get. The manual didn't say anything about peak voltage, what is that about?
                Peak voltage refers to testing AC volts. AC volts rise from 0 to a certain value then lower to 0 then go below 0 to a certain value and then back to 0. You are trying to capture the maximum voltage value as the value is rising and falling repeatedly. A peak voltage adapter is typically used on a normal volt meter. Even though checking for maximum (peak) AC volts the meter is set to the DC setting.

                Comment

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