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2003 GTI (717) Backfiring through Carb

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  • 2003 GTI (717) Backfiring through Carb

    I have just completed a rebuilt on a the motor of a 2003 GTI.
    Crank Rebuild, Bore and new pistons, Carb rebuild. Starts fine each time but is backfiring badly through the carb.

    I have triple checked each of the following.

    RV timing is checked and correct.
    Leak Test carried out on the Cooling Circuit, crankcase and RV system. All passed fine.
    Flywheel key is fine.
    Good Compression.
    Magneto coil was marked before removal and reinstalled in same position.
    Charge coil and generating coil test as per the manual, both working fine.
    Also checked the crank for correct alignment. Also fine.

    I swapped each of the following from a working ski and still have the problem

    Rectifier. MPEM. Ignition Coil.

    The only thing I have not checked is the ignition timing using the timing light as per the manual.

    Does anyone have any other ideas as to what is causing this problem.

  • #2
    Re: 2003 GTI (717) Backfiring through Carb

    How old is the fuel you are using? Do you have the right spark plugs in it? Whats the battery voltage while cranking, must be at least 10.5 volts while cranking.
    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

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    • #3
      Re: 2003 GTI (717) Backfiring through Carb

      New Plugs fitted and gapped to spec.
      Battery Voltage Good.
      Not sure about fuel it has been in there for about 4-5 months now.

      As regards timing is it necessary to have a tachometer to carry out this procedure or will a timing light suffice.

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      • #4
        Re: 2003 GTI (717) Backfiring through Carb

        The timing should be close enough, what is your pop off set at, you might be getting way to much fuel in the motor.
        SBT Tech Support is here to help with your problems.
        We try to answer each question quickly and accurately.
        Please do not use Private Messaging for Tech Support, use the forums.

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        • #5
          Re: 2003 GTI (717) Backfiring through Carb

          Originally posted by steelroe View Post
          ......RV timing is checked and correct.
          Does anyone have any other ideas as to what is causing this problem.
          How are you checking the RV timing? If you are checking with the engine installed, and looking down from the top of the engine, the timing is most likely backwards....I have seen this many times, sometimes even the pro's can make mistakes.....Check the RV timing one more time, and make sure you have Mag piston at TDC, and set the RV closing timing for the mag cylinder at 65°
          John Kubiak
          Powersports Technical Training Professional
          Las Vegas, Nevada
          Sea-Doo Tech 13736
          PWC Tech since 1988 (22 years)
          PowerSports since 1976 (34 years)
          NEVER BUY TIRES AT A "BLOW-OUT" SALE
          Please do not use Private Messaging, use the forums.

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          • #6
            Re: 2003 GTI (717) Backfiring through Carb

            I have checked the RV timing with the engine in and out of the ski. I used the timing procedure on the tech section of this site.
            Not sure what pop off os currently but I re-used the original spring so I would have assumed it was correct. Needle and seat also fine. Will check pop off tomorrow.

            Any other ideas please post up.
            What is the easiest way toset the ignition timing?

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            • #7
              Re: 2003 GTI (717) Backfiring through Carb

              Please tell us EXACTLY the type of plug you have installed.
              Dan Solie -
              04 RXP (the "Instigator")
              94 xp (freestyle mods)
              95 xp (faster than the 94)
              JS550 (the toothpick & the loaner)

              For FREE Seadoo Manuals - Click HERE!!!!

              http://www.tripleateam.com/water/v/U...ery/Dan-Solie/

              **** Please do not PM me. I don't do PM's.... Please post your question on the correct forum so that all can see and learn. Thanks! ****

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              • #8
                Re: 2003 GTI (717) Backfiring through Carb

                NGK BR8ES Gapped to 0.5mm

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