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  1. #61

    Join Date
    Sep 2010
    Location
    Lake Travis, TX
    Posts
    43
    If your carb disassembly doesn't reveal any obvious problems, you might consider doing a leak down test on that engine. You might have an air leak somewhere that is causing your lean condition on that rear cylinder.

    Mike


  2. #62

    Join Date
    Jul 2015
    Location
    Chattanooga, TN
    Posts
    130

    Pop Off Too Low on Stock 1200 PV (66V)?

    Quote Originally Posted by TwoGP12s View Post
    If your carb disassembly doesn't reveal any obvious problems, you might consider doing a leak down test on that engine. You might have an air leak somewhere that is causing your lean condition on that rear cylinder.

    Mike
    If refreshing the fuel pump side of the carbs doesnít fix the issue, Iíll do as you said and pressure test the engine.

    I resealed the cases 2 years ago, and they held pressure. Didnít use the boat hardly at all last year due to pregnant wife, so hopefully itís not already leaking again.

  3. #63

    Join Date
    Jul 2015
    Location
    Chattanooga, TN
    Posts
    130
    Took boat out again today. Left motor bogged and RPMs were low. Like itís running lean.

    Right motor felt very responsive and strong, just like it did right before it melted the piston.

    Right motor spark plugs

    Front
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    Middle
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    Rear (the one that previously melted a piston)
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  4. #64

    Join Date
    Jul 2015
    Location
    Chattanooga, TN
    Posts
    130
    Left motor spark plugs. Was bogging out today

    Front
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    Middle
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    Rear
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  5. #65

    Join Date
    Nov 2017
    Location
    The Shores, Mitten
    Posts
    119
    +1
    6
    I went through hell with a 66V, pulled the carbs 12 times making fueling adjustments. READ THE MIKUNI MANUAL: https://www.mikuni.com/pdf/sbn_manual.pdf

    Idle - adjust low speed screws adjustments
    Idle to 1/3 throttle - low speed jet and pop-off pressure adjustments
    1/3 to 3/4 throttle - high speed jet adjustment
    3/4 to WOT - high speed screw adjustment

    You match the bog/rich misfire/load-up conditions to the throttle position and adjust the circuit. Adjusting the low circuits will impact the high circuits.

    READ THE MIKUNI MANUAL, it works and is the only resource for these I-body carbs and from my recent experience it is applicable: https://www.mikuni.com/pdf/sbn_manual.pdf

    I went from bogging off idle over and over and over to beating a 2018 GP1800 off the line (holeshot only).

  6. #66

    Join Date
    Jul 2015
    Location
    Chattanooga, TN
    Posts
    130
    Quote Originally Posted by steelmesh View Post
    I went through hell with a 66V, pulled the carbs 12 times making fueling adjustments. READ THE MIKUNI MANUAL: https://www.mikuni.com/pdf/sbn_manual.pdf

    Idle - adjust low speed screws adjustments
    Idle to 1/3 throttle - low speed jet and pop-off pressure adjustments
    1/3 to 3/4 throttle - high speed jet adjustment
    3/4 to WOT - high speed screw adjustment

    You match the bog/rich misfire/load-up conditions to the throttle position and adjust the circuit. Adjusting the low circuits will impact the high circuits.

    READ THE MIKUNI MANUAL, it works and is the only resource for these I-body carbs and from my recent experience it is applicable: https://www.mikuni.com/pdf/sbn_manual.pdf

    I went from bogging off idle over and over and over to beating a 2018 GP1800 off the line (holeshot only).
    Yeah man, I live and die by that manual. The rear carb is setup identical to the front and middle.

    I need to get around to pressure testing the motor to make sure I donít have a leak.

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