Finbro 26.5/22mm head & 143cc BBK rev limit
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Finbro 26.5/22mm head & 143cc BBK rev limit

This is a discussion on Finbro 26.5/22mm head & 143cc BBK rev limit within the Grom Talk forums, part of the Honda Grom Forums category; Installed the older Finbro 26.5/22mm head on my bike and forgot if it came with heavier valve springs or not, does anyone remember? What is ...

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Thread: Finbro 26.5/22mm head & 143cc BBK rev limit

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    Finbro 26.5/22mm head & 143cc BBK rev limit

    Installed the older Finbro 26.5/22mm head on my bike and forgot if it came with heavier valve springs or not, does anyone remember?

    What is a safe range to set my rev limit to?

    I'm running a Kitaco type 2 cam on a 143 Tak bbk, so I need that top end power.

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    I run my 143 up to 11k but Im running a ported head with upgraded retainers from DHM.
    2015 Grom - High Compression 125 Build
    2018 Grom - 143cc BigBore
    1986 Spree - 70cc BigBore
    2017 DRZ400SM

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    I would just install the dual valve springs regardless. Then you know for sure you can spin it up to 11K and you'll be squeezing all the potential out of it.
    Quote Originally Posted by Paultergeist View Post
    It seems like there is always one more thing to buy, THEN I’ll really notice a difference in performance.

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    Yeah... I probably should and will later but I just don't have the time right now to take the head off again to change the springs.

    What's a safe rev limit for stock springs?

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    Quote Originally Posted by Cheburashka View Post
    Yeah... I probably should and will later but I just don't have the time right now to take the head off again to change the springs.

    What's a safe rev limit for stock springs?
    Safe rev limit with stock springs is pretty much stock limit... they float shortly thereafter.

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    If its a finbro head, it likely came with the stiffer finbro valve springs. I rev my 164 with a 27/23mm valve head to 12.5k from here n there and never had issues. I definitely dont do it on the regular.

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    Quote Originally Posted by farkas View Post
    Safe rev limit with stock springs is pretty much stock limit... they float shortly thereafter.
    I've been running my stock cylinder close to 10k rpm where I set the limit. What's the sign of a floating valve?

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    Quote Originally Posted by Leo310 View Post
    I've been running my stock cylinder close to 10k rpm where I set the limit. What's the sign of a floating valve?
    Without opening the motor up and looking for contact between the piston and valves, you can't know for sure. Sometimes there won't be any contact between the valve and piston, but the valves are floating. Its really hard to tell without doing a back to back comparison against a similarly set up motor with stiffer valve springs.
    Last edited by solidjohnny; 08-23-2019 at 03:01 PM.
    Quote Originally Posted by Paultergeist View Post
    It seems like there is always one more thing to buy, THEN I’ll really notice a difference in performance.

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