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'93 Yamaha 200HP Knocking after adjusting carbs

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  • '93 Yamaha 200HP Knocking after adjusting carbs

    Hi everybody, my 1993 Yamaha 200HP started knocking after I adjusted the carbs per OEM Yamaha Service Manual specifications, when I was checking the adjustments screws they had different settings, so as per the book, I adjusted Port Screws 1 1/4 and Starboard Screws 3/4, now the engine runs a bit better, but I can hear a constant knocking coming from the head, engine does not surge it runs smooth and also the the Idle speed when down after the adjustment, it was almost at a 1000 RPM nos is around 800 RPM, any ideas what could have cause this issue, maybe lean mix?

  • #2
    Pinging is the result of either lean fuel mix or very advanced ignition timings or high operating temps.
    Maybe the cleaning procedure needs repeating or cleaning your carbs revealed an issue you werent aware of.
    Also note that the initial carb pilot screw settings may need adjustment in water
    Last edited by axolotl98; 04-20-2011, 11:38 AM.

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    • #3
      you have other issues.
      there is no initial setting that needs adjustment if everything is correct.
      the carb pilot fuel needle does NOT adjust air to fuel ratio on that carb.
      air to fuel ratio is determined by the pilot air jet and the pilot fuel jet.
      all that needle does is allow more or less of this jetted mixture.\

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      • #4
        Why do the port and stb pilot screws have different adjustments. My '98's are the same way.
        1999 Grady Sailfish SX225 OX66
        1998 Grady Tigercat S200 lightening strike (totalled)

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        • #5
          I checked the timing and it was off by almost 4 degrees, book says ATDC 7 degrees +/- 2 degrees and it was on 4 degrees now it does not sound as bad as before, but Im sure theres something else, I have had this boatf for a few months now and I have been using it the way it was several times and it always runned good, a bit rough but always started right up and runned strong at full throttle, thanks anyway for your help guys.

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