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Discussion Starter #1
I plan on updating my Primary Sheave this fall so I was searching for spring options for tuning.

I am not sure on the specs of our Secondary Clutch Spring or the Finish Rate, but I'm posting what I find for tuning options.
Looks like EPI has 2 options:
https://epiperformance.com/secondary-6/
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Spring Options.jpg
 
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Discussion Starter #2
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I haven't heard of them either and would really like to hear from anyone with 1st hand experience with these springs. Glad you brought this up. I'm also looking to upgrade to the HW sheaves in the spring so I'd really like to hear from those that have tried this spring with that setup.
 

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EPI is big in the Polaris World. I had one of their kits in my Ranger. It was good. For Yamaha, stick to JBS or Hunterworks and what they recommend. More than likely secondary isn't needed in the X platform but listen your sheave grinder.
 

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Discussion Starter #7 (Edited)
Basics with what we have to tune.

-Stiffer Secondary Spring Finish Rate = Slower Upshift, Faster Backshift
-Softer Secondary Spring Finish Rate = Faster Upshift, Slower Backshift

-More Primary Clutch Weight = Less RPM & greater belt squeezing force
-Less Primary Clutch Weight = More RPM & less belt squeezing force

Roller weights basically set the belt squeeze force as it relates to RPM's to overcome the Secondary Spring rate. (Shift Phase)
You will also notice a difference in engine braking depending on your tune.

I'm after performance, so I want the shift phase to happen close to the motors powerband w/o being to annoying.
It's a fine line as you can cause some ill effects such as a jerky throttle or engine braking to soon.

I probably won't do any testing until later this Fall/Winter depending on work schedule.
Just thought I would post some info for others and if anyone does any tuning, let us know what you think.
I need to find the rates of our stock spring also.
 
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Discussion Starter #8
Right, right, but I'm going to tune a stock sheave to my liking first, then when I upgrade, I'll be able to really notice the smalls and see if it was worth it. ;)
And yes, I'm going to shim out the stock primary too for more bottom. :p

EPI is big in the Polaris World. I had one of their kits in my Ranger. It was good. For Yamaha, stick to JBS or Hunterworks and what they recommend. More than likely secondary isn't needed in the X platform but listen your sheave grinder.
 

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Blaze that trail, bud. We are behind you 100% and appreciate what you do.
 

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Discussion Starter #11
Just purchased EPI's green spring as I want to see how it compares to stock.
Still running stock sheaves with 18g HV weights at the moment.
I'm still leaning towards the Hunterworks sheave and will probably have it on hand when I do the spring change so after test runs w/ the spring I can install it while the plastics are off.
That way I'll know exactly how each component adds to the performance and tune.

The HV weights are still performing flawlessly along with Tinkseal.
Both are great products and I still highly recommend.
Link: Hunterworks.com/wolverine_x2_x4_
 
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Discussion Starter #12 (Edited)
EPI Spring arrived.
Took some pics and measurements.
Measurements are rough as spring is powder coated and I can flex it slightly compared to OEM, so measurements are for comparison only.
Right off the bat,
-The wire diameter seems much smaller.
-Spring feels softer in initial movement.
-Spring seemed shorter, so I took rough measurements.
Since it's powder coated and has some initial movement compared to stock, it's a little harder to nail down, but I get readings anywhere from 4.785" - 4.825"
OEM spring with 2600+ miles reads a dead 4.841" every time with no initial movement.
Just thought I'd share the info.....

Pics of new and old spring for comparison.
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90915

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90916

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90917

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90919
 

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Discussion Starter #13
I don't have access to a press w/ a gauge or I would weld up some pipe sleeves for safety and check what our OEM spring pressure is at 3" & 2.2" for comparison.
If anyone does this, it would be cool if you added the info :D
 

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Discussion Starter #15
It could be.
I spent a lot of time searching the net for clutch tuning components and EPI was the only place I found springs.
There could be others, I just didn't find any at the time.
 

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Discussion Starter #16
I had some concerns with the green spring so I ordered the yellow spring too.
Just another tuning option in the box that I can try if I decide I don't like how the green performs.
You know me......I'll update with pics and measurements once it arrives.....lol
 

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Discussion Starter #17 (Edited)
Just got some very helpful information from the Clutch Guys @ EPI, so thought I'd share.

The stock X2 secondary spring is below.

3.0” - 2.2”

Stock 295 – 455

YDS9 Green 330 – 495

YDS10 Yellow 360 – 540

Edit: adding differences from OEM
Green 35 - 45
Yellow 65 - 85
 
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Discussion Starter #18
So with all components staying the same, it appears that the springs offer slower upshifts and faster backshifts rates.
I don't see slower upshifts as a bad thing as it's about finding where in the powerband that you want the shift phase to happen.

I just purchased the Hunterworks Sheave and now I have more information about the spring comparisons, I can tune to my riding style for my terrain.
 

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Discussion Starter #19
Yellow spring arrived.
I'm not going to bore everyone with measurements and specs.
Doesn't seem to be any interest and I'm going to stop talking to myself.....lol
Anyway, here is a pic. We love pics....lol.
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91001
 
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I'm following. You're not just talking to yourself!
 
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