96 Kawasaki 750sxi flames under carbs in intake - Page 5
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  1. #41
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 96 Kawasaki 750sxi flames under carbs in intake

    5 thou can easily be a casting difference on the head or cylinder.

    How about those ac voltage numbers?
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
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    '99 Yama GP1200 65U 61.8 GPS
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    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  2. #42
    PWCToday Newbie Acguy's Avatar
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    Re: 96 Kawasaki 750sxi flames under carbs in intake

    I replaced the voltage regulator and igniter with OEM parts today( igniter was after market and the regulator was original). I checked spark and then found a plug that wasn’t sparking consistently and replaced it. I now have strong spark both plugs. Back to where I was before moving parts all around
    I sprayed starter fluid in and it started right up.
    I didn’t get a chance to do more, I will check it out tomorrow night and post outcome.

  3. #43
    Resident Guru JC-SuperJet's Avatar
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    Re: 96 Kawasaki 750sxi flames under carbs in intake

    Can't believe you just now installed an OEM CDI...

    Anyway, when you started the Engine, do you still see flames in the Intake?

  4. #44
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    Re: 96 Kawasaki 750sxi flames under carbs in intake

    I actually changed ignition coil and regulator yesterday and did a quick bump confirming spark issue is resolved. Chasing the back fire issue I lost spark on one plug. I have been moving parts around a lot. Now I am back to where I was, still backfires!
    I have two good CDI oem boxes and neither solved my problem.
    Flywheel key ok
    Stator rebuilt, checks out electricity
    New ignition coil
    New regulator
    Removed rubber coupling between exhaust and water box, which confirm no restrictions at water box . still back fired
    Rebuilt carbs with oem kits
    Replaced intake cages and reeds
    Confirmed no crank twist, rear piston in lower .005 at tdc

    Today (hasn’t started it in a month due to spark issue)it starts up easily once warmed up. It’s Boggs when on and off throttle and will eventually back fire into intake.

    MySelf. I didn’t fully get all the electrical checks you suggested

  5. #45
    Resident Guru JC-SuperJet's Avatar
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    Re: 96 Kawasaki 750sxi flames under carbs in intake

    When you rebuilt the Carbs, did you also install new Needle Valves? If they're old, they might be leaking/dribbling fuel. Did you test the pop-off pressure? How much pop-off pressure?

    Can you look down the carb throat(s) and see any fuel dribbling while engine is idling?

    What jetting do you have in the carbs?How many turns on the Low and High Speed Screws?

    Post some pics of your engine bay to see your engine setup.

  6. #46
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    Re: 96 Kawasaki 750sxi flames under carbs in intake

    I did not change the needles. I did pull them and inspected with a magnifier, there was no wear. The main and pilot jet are confirmed stock(147.5, 67.5). Pop off pressure was 22-24 psi. The ski would not idle at 1/2 turn out, I had to adjust it to 3/4 to idle. High speed is at 1 turn out. I have not noticed fuel dripping, but I will check that.
    Canít figure out how to post pics to a reply, will work on it

  7. #47
    Resident Guru JC-SuperJet's Avatar
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    Re: 96 Kawasaki 750sxi flames under carbs in intake

    Jetting, Screw Adjustments and Pop-Off are typical and look normal for a completely Stock SXi.

    A Needle Valve can also leak past the Seat(Valve Body) O-Ring even if the Viton Tip is good. O-Rings do shrink and degrade over time. See pic.

    But if you did a proper Pop-Off Pressure Test(you did wet/drench the Needle Valves with WD-40 before pressurizing?) and the Valves popped cleanly without any bubbling or fizzing prior, then the Needle Valves are holding like they should.

    Keihin CDK Needle Valve.jpg

    Keihin Carburetor Rebuild SBT.pdf See 1.6
    Last edited by JC-SuperJet; 01-21-2020 at 07:53 AM.

  8. #48
    Resident Guru JC-SuperJet's Avatar
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    Re: 96 Kawasaki 750sxi flames under carbs in intake

    I read the entire thread again. Even took notes...lol

    So BEFORE the Engine rebuild, the Engine would shut-off when turning or when full throttle was applied, but there were no flames/blowback into the Carbs, right?

    THEN you installed a new Top End and now there are flames coming up the Intake Manifold.

    I think the Pistons are installed backwards. The Ring Gaps need to be on the Intake Side.

    If the Piston Ring Gaps are on the Exhaust Side (the wrong side), the Flame Front would easily blow-by the Ring Gaps into the Crankcase and past the Reeds, up the Intake Manifold, , to the Carb Throats.

  9. #49
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    Re: 96 Kawasaki 750sxi flames under carbs in intake

    Last summer the ski started up easily and ran ok. It did stahl while turning sharp. It did feel slow at full speed and I don’t think it was running right. The summer issue was while turning sharp.
    I pulled the engine and re built it. I was aware of piston placement and I think I did it right. The rings I think only went on one way. The pro-x pistons had a mark where the ring gap went. I will pull the head and confirm pistons are in correct.
    Yes this problem did start after the engine rebuild and carb rebuild.

  10. #50
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    Re: 96 Kawasaki 750sxi flames under carbs in intake

    Oh no....JC might be onto something.
    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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