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  1. #1
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    Tuning a centrifugal clutch for hill climbing

    Would a higher engagement rpm help with hill climbing?

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    If the engagement is set to an rpm closer to your power band - yes it should. Engagements set too low will definitely affect hill climbing as the rpms struggle to get into the engines power range.

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    Is it possible just to cut a few loops off the spring to tighten it up?

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    I run a Hilliard clutch and just swap springs. I would not cut them. Springs are relatively cheap so just buy a couple with different engagements.

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  6. #5
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    Hopefully your gearing is where you want/need it.

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  8. #6
    Havasu Dave's Avatar
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    Quote Originally Posted by SAS289 View Post
    Hopefully your gearing is where you want/need it.
    Exactly. The clutch engagement is only for initial acceleration, and will do nothing once shoes are engaged at whatever RPM the springs dictate.
    Has anybody seen the bridge?

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  10. #7
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    Good point. I put a 60 tooth rear sprocket on my Coleman 200 EX, but maybe I need more. I was able to climb the hill in question initially with a bit of clutch grab/release at the very top but have since the ability to get to the top despite a few mild engine mods that have improved power. I haven't smoked the clutch at all, but it is possible that some of the grease I used on the needle bearing (white lithium) has migrated out. I'll give it a good cleaning, scuff up the contact surfaces, and see what that does.

    The more I think about it, higher engagement RPMs would help you get started up a hill, but if the clutch is disengaging on the hill, you would need more power or more gear. My 225 lbs isn't helping anything, either!

  11. #8
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    Here is a climb I made on the hill in question right after I changed the sprocket. Now I stop 10 ft shy of the top.


  12. #9
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    Hmmm, maybe I need more posts before I can post a link...

  13. #10
    Senior Member TheDullCarbide's Avatar
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    Quote Originally Posted by MJL View Post
    Hmmm, maybe I need more posts before I can post a link...
    Yes you do.

    Honestly, you have to tune the clutch by feel, not rpm. You need to "feel" where your TORQUE band is in your engine and tune your clutch have a stall right at your peak TORQUE rpm. Then you need to gear to have your engine pull the majority of the hill at the rpm of peak POWER. This combination will get you up the hill as FAST as possible (gearing for peak power) and it will be able to provide the most torque available even if the clutch starts to slip (clutch stall at peak torque).

    Also, this is the perfect application for a TC. A TC can keep your engine at peak power (get up the hill FAST) at a wide range of ground speed whereas a clutch will only provide a single ground speed at peak power. A TC should be tuned to stall at the engine's peak torque and shift at the engine's peak power. In the end, think of it as a clutch that automatically tunes the gearing to achieve peak power dependent on ground speed.
    Last edited by TheDullCarbide; 01-12-2018 at 05:15 PM.

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