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  1. #1
    Chine Walker
    Join Date
    Nov 2006

    Does raising compression increase the idle?

    All things being equal; in this case on a EFI 1300 motor??



  2. #2
    I would think that it could, yes.

  3. #3
    In theory, it should only at idle when NOT in the water. The IAC stepper motor opens the throttle blades when the motor is loaded at idle by the ski being in the water, to keep base idle the same, in or out of the water, controlled by the PCM.
    Out of the water, the IAC stepper motor is not opening the throttle blades and the engine only gets the base idle air from the idle set screw adjustment.
    More squeeze, bigger bang from the same amount of fuel and air should create a slightly higher idle out of the water.
    Last edited by rossnemo; 04-03-2008 at 11:17 PM.

  4. #4
    Chine Walker
    Join Date
    Nov 2006
    Is there an idle adjustment screw on the TBs?


  5. #5
    Yes there is. It is very hard to see and harder to get at on while they are mounted on the ski. It can be done but its tricky.
    8mm nut holds a very small allen setscrew in place for base idle.
    Many times the setscrew siezes in the threads and is extremely hard to turn. Maybe its loctited from Yamaha, not sure.

  6. #6
    Chine Walker
    Join Date
    Nov 2006
    Thanks Ross. Lowell recmended that I try to raise the idle to @ 2000 rpm while trolling; seems it's better for 2 stroke motors. Will this adjustment mess with the ECU. Will I need to adjust cable tension after?


  7. #7
    If you set the base idle for 2000 rpm in the water with the idle set screw, you are going to have an idle flare when its out of the water.
    The PCM controls the idle speed in the water, via the stepper motor, and there isnt anything you can change there, its in the software..

  8. #8
    Chine Walker
    Join Date
    Nov 2006
    Ok, thanks Ross, I'm not going to fool with it.
    Once I get the EFI controller, I'll if that changes anything with the idle circuit.
    On a different note, I need to see if the butterflies open fully when the throttle is maxxed.

  9. #9
    Chrisrokc's Avatar
    Join Date
    Apr 2006
    Oklahoma City, OK
    Ditto what Ross said. If you change it everything will be screwy I think. My idle was funky out of the water even when it was a 1300. Now it is ok for awhile then gets funky. In the water though it stays normal.

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