Yamaha FX HO Misfiring?
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  1. #1
    PWCToday Regular
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    Yamaha FX HO Misfiring?

    2015 model with about 50 hours. It always started up almost instantaneously, even the first time after sitting all Winter. This year it cranks for a few seconds when cold, and starts up good when warmed up. I'm reporting this to show a difference in perceived performance, not necessarily a problem.

    The last 2 times out after leaving the dock and accelerating up to cruising speed it would balk as though it was missing. The " sputter" for lack of a better term, was not continuous, but it would "miss" every 15 seconds or so. It After about 10 minutes it ran smooth at cruise speed for the rest of the day.

    At idle in forward (no wake speed setting) it also runs a little rough all the time.

    I got no alarms or warning codes. I don't have no way to personally check the ECM.

    Any suggestions where to start?
    Jim

  2. #2
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: Yamaha FX HO Misfiring?

    Jim, this is very common with all the 4 strokes. Install new spark plugs every season.
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  3. #3
    PWCToday Regular
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    Re: Yamaha FX HO Misfiring?

    I replaced the plugs and it completely solved the problem. The old plugs looked perfect when they came out, so I was somewhat surprised at the result.

    Thanks for the help...
    Jim

  4. #4

    Re: Yamaha FX HO Misfiring?

    I had a similar experience with my Sea Doo, replaced 3 perfectly fine “looking” plugs and it ran as smooth as can be.


    Sent from my iPhone using Tapatalk

  5. #5
    PWCToday.com Is My Home Away From Home SxiPro's Avatar
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    Re: Yamaha FX HO Misfiring?

    Ain't it wonderful when a problem can be solved for less than the price of a six pack?
    Changes aren't permanent, but change is.

  6. #6
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: Yamaha FX HO Misfiring?

    My theory is a combination of a pretty hot ignition and sustained high rpm's lead to an early plug failure.
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

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