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  1. #1
    PWCToday Newbie b00st's Avatar
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    300SX vs JS300 flywheel?

    Does anybody know if there's any timing differences between the 300sx and js300 flywheels?

    We bought a 300sx a while back (not running) and found out one of the magnets fell off of the flywheel and took out the stator, so we replaced the stator and flywheel. Well the "300sx flywheel" we bought turned out to be a js300 flywheel. I know its a js300 flywheel due to the fact that 300sx flywheel has no indentation where the flywheel bolt bolts into and the js300 flywheel does. I was able to machine a "shim" and make the flywheel fit perfectly but I think I am running into a timing or tuning issue.

    It seems to have a "spark knock" when you go to give it gas. I am able to get it to idle fine and I do not hear the knock at idle but when you give it gas it spark knocks and bogs out. I think it could also be the carb needing adjustment since I cleaned the carb and forgot to count how many turns in the adjuster screws were out, but after trying to tune it for an hour I figured it had to be a timing issue.

    I used to have a timing light somewhere, but I can't seem to find it so I figured I may as well see if anybody knows right away if there's a timing difference in the flywheels before I go and do that. Otherwise I guess I will go out and buy one and see what I can find.
    Thanks a lot guys.
    '85 JS550/750: ~Small pin/dual carb~ (Completed 6-7-18)
    '91 300SX

  2. #2
    PWCToday.com Is My Home Away From Home WFO Speedracer's Avatar
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    Re: 300SX vs JS300 flywheel?

    somewhere in my stash I have one of these flywheels
    Y'all know me, still the same O.G. but I been low-key
    hated on by most these &^$$@s with no cheese, no deals and no G's, no wheels and no keys, no boats, no snowmobiles, and no skis, mad at me cause I can finally afford to provide my family with groceries


  3. #3
    I dream skis
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    Re: 300SX vs JS300 flywheel?

    Iím pretty sure they are the same , you could check part numbers to confirm.

  4. #4
    PWCToday.com Is My Home Away From Home
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    Re: 300SX vs JS300 flywheel?

    flywheel is a different part number because it has provisions for the oil pump.this is the only difference afaik.all the other electrics are the same however.
    if the wheel you have bolts up,run it as timing is the same.

  5. #5
    PWCToday.com Is My Home Away From Home WFO Speedracer's Avatar
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    Re: 300SX vs JS300 flywheel?

    both the 300sx and regular 300 have oil injection.
    Y'all know me, still the same O.G. but I been low-key
    hated on by most these &^$$@s with no cheese, no deals and no G's, no wheels and no keys, no boats, no snowmobiles, and no skis, mad at me cause I can finally afford to provide my family with groceries


  6. #6
    PWCToday Newbie b00st's Avatar
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    Re: 300SX vs JS300 flywheel?

    Ok so I figured out the issue. Timing was advanced too much. My flywheel key was too small (had to replace it with a generic autoparts store key since I lost mine when I removed the flywheel) so when I tightened down the flywheel, it was able to move the flywheel a little off center from the key which caused timing to be way off. I fixed it by ordering the correct key and it ran a whole lot better and doesn't knock anymore.
    Anyways I found the old flywheel in the trash and was able to confirm, the magnets were the same and everything is the same other than the indentation where the flywheel bolt goes which can be fixed with a shim.
    Here is a pic:
    The one of the left is a 300sx flywheel and the one on the left is a js300.
    '85 JS550/750: ~Small pin/dual carb~ (Completed 6-7-18)
    '91 300SX

  7. #7
    PWCToday.com Is My Home Away From Home
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    Re: 300SX vs JS300 flywheel?

    different oil pumps on js and sx dictate the change in flywheel.retaining bolt is different as well.

  8. #8
    PWCToday Newbie b00st's Avatar
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    Re: 300SX vs JS300 flywheel?

    Yep probably. Our 300sx was already setup for premix so with just a shim we were able to use the js300 flywheel. Took it out for the first time today and it such a fun ski to ride.
    '85 JS550/750: ~Small pin/dual carb~ (Completed 6-7-18)
    '91 300SX

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