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  1. #1
    Sanfish's Avatar
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    Upgrade Valve Springs & Retainers = Lost Speed and RPM?

    Trying to sort something out...

    If everything being equal, could running aftermarket (REV) valve springs and Ti retainers cause about 120-150 RPM loss and around 1 to 1.5MPH loss? (or more)

    Base; '13 RXPX, 4" Kani, IMUK, RRFPR, VT8375.


  2. #2
    Mod less, ride more! troyheb's Avatar
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    Yes. Not unheard of.

  3. #3
    Sanfish's Avatar
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    Thanks for replying TH.

    Please keep this going, I really like to hear from as many as possible for a general consensus. Especially personal experiences (yes or no).

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  5. #4
    ncdoo's Avatar
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    I have wondered the same. Seems like stronger valve spring would have to rob you of some HP.

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  7. #5
    Mod less, ride more! troyheb's Avatar
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    When I had my 08 PX, it seemed like they "loosened up" a little after a few hours. But that my have just been my imagination.

  8. #6
    R88ory RXP's Avatar
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    Cam timing has a big effect on these motors too, so you may not have got the cam exactly where it was before you took the head off to do the valves.

    R88


  9. #7
    WickedXP's Avatar
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    Quote Originally Posted by Sanfish View Post
    Trying to sort something out...

    If everything being equal, could running aftermarket (REV) valve springs and Ti retainers cause about 120-150 RPM loss and around 1 to 1.5MPH loss? (or more)

    Base; '13 RXPX, 4" Kani, IMUK, RRFPR, VT8375.
    With the stronger springs you can retire the 8375 tune and spin the 8600

  10. #8
    JT jpt7779's Avatar
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    The most common reason guys see this kind of performance loss is the weather. High air temps, high humidity, pressure below 30.00", high relative density altitude, kills 150-200 rpm easy.

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  12. #9
    Sanfish's Avatar
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    Quote Originally Posted by R88ory RXP View Post
    Cam timing has a big effect on these motors too, so you may not have got the cam exactly where it was before you took the head off to do the valves.
    Not sure why you assumed head was removed or that timing wasn't checked. This isn't the case here.

    Quote Originally Posted by WickedXP View Post
    With the stronger springs you can retire the 8375 tune and spin the 8600
    This has nothing to do with this OP. Besides, raising RPM doesn't make engine spin higher while in water. Especially if not hitting 8375 limiter.

    Quote Originally Posted by jpt7779 View Post
    The most common reason guys see this kind of performance loss is the weather. High air temps, high humidity, pressure below 30.00", high relative density altitude, kills 150-200 rpm easy.
    Yes, but again, not related to this case.

    I appreciate the feedback but please be aware it wasn't an accident when I wrote "everything being equal." This is less about my ski and more about the act of changing these parts and the outcome while all others variables being equal.

  13. #10
    WickedXP's Avatar
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    Did you think upgrading the valvetrain would give you more power then? The whole reason for this upgrade is is to turn higher RPM's safely. Not sure what you were looking to gain by just doing Rev springs and TI retainers???

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