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Discussion Starter #1 (Edited)
--------Update 5/03/2012--------
Known working applications for PATV1
2000 Trail Boss 325 (factionfx)
2011 Sportsman 400 (rooskey)
2012 Sportsman 500 (factionfx)
2009 Sportsman 500 x2 (highmark)
2001 Sportsman 500HO (centexguy)

--------Update 4/25/2012--------
This mod should work on the just about every 4-stroke Polaris machine that is NOT AN XP 550/850. Not sure about RZRs or Rangers.

As you can read through this thread, we have some people using it on the 800 EFI, 400, and of course 500 sportsman, from all different years. I just installed one on my 2000 Trail boss 325. Have not been able to ride it yet, but it appears to perform correctly.

For the 2-stroke crowd, this spring will not work. There are different options for spring-only replacement but I am not sure what they are yet. RENOBADBOY has a 300 2stroke and has been playing with the springs. Let me know and I will put up here what he says.

--------ORIGINAL POST BELOW--------

Hey guys, In the recent past i have talked up the notion just ordering an EPI PATV1 (red) primary spring for the Sportsman 500 instead of going for a full blown clutch kit.

I'm sure it's not the full effect of a clutch kit, but from emailing EPI tech support, it offers a 400 rpm increase in engagement RPM, and 200 rpm on the top.

And it is $25 on amazon.com versus 200+ for a clutch kit.

And it's easier to install. You don't even have to pull the clutch. Just the 6 bolts out of the cover. (Note that I torqued my cover bolts to 12 ft lb with a quality torque wrench....spec is slightly lower at 8-10ft-lbs but mine did not go that low).

Torque on primary clutch retaining bolt is 40 ft-lbs.

Anyway, I was going through my pictures and found some of it, and how it compares to stock, for what it's worth.

Remember that the clutches are balanced from the factory, so draw X's on it as in the pictures below so that you get it lined up correctly when re-assembling.

Stock is blue-green
EPI is RED

Enjoy!
 

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I just installed this spring on my stock 500 to gain back some of the power lost from the 27s in run now. It helped alot and still drives good.
 

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Excuse my total ignorance in the land of CVT, but how does this benefit? By raising your engagement RPM there would be more power when you start rolling helping turn the bigger tires?

There is always a trade off for everything you do, so what would the downside be? The engine works harder by requiring more RPMs? Loss of top speed?
 

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Just make sure you get the cover back on the same way. Line the Xs up.
 

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Excuse my total ignorance in the land of CVT, but how does this benefit? By raising your engagement RPM there would be more power when you start rolling helping turn the bigger tires?

There is always a trade off for everything you do, so what would the downside be? The engine works harder by requiring more RPMs? Loss of top speed?
When you put on bigger tires you change the overall gear ratio. The clutch is calibrated for the stock tire size so that the engine will stay in the peak powerband as much as possible. Changing the spring and/or the weights you "recalibrate" your clutch to compensate for the new overall gear ratio.
 

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What rpm does the red one engage at?
 

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Discussion Starter #9
Excuse my total ignorance in the land of CVT, but how does this benefit? By raising your engagement RPM there would be more power when you start rolling helping turn the bigger tires?

There is always a trade off for everything you do, so what would the downside be? The engine works harder by requiring more RPMs? Loss of top speed?
Yes it basically just shifts the usable power curve...instead of engaging when your bike has 15 horsepower it engages at 17 horsepower.

There is a power and torque chart on the aaen website

Sent from my NookColor using Tapatalk
 

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Discussion Starter #10

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It does great. My 2011 400HO really liked it. And like you said for twenty-five dollars you cant beat it..
 

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Discussion Starter #12
What years will this work on?
As far as I know it will work on just about all 325cc-500cc 4-stroke polaris.

I only say this because I had emailed the guy at EPI back and ask him what he recommended for my 2000 Trail boss 325 and he said the same spring.

Good luck!
 

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Just ordered one off Amazon from Powersport Superstore. $23.31

Anyone running the spring with just stock tires? Any benefit?

I plan on going to 26" BH2 sometime soon, which they run a size larger than listed. Wanted to pick up this spring and some spacers before I get the tires.
 

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It has nothing to do with the size of tire. It has everything to do with the weight of the tire. Most people dont consider this. Take a closer look at how much extra rotating weight you will be hauling. I bet that you will be surprised...
 

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Received the spring today. Probably won't install it until I get new tires. Waiting for RDC to get spacers in stock before I order tires.

Sent from my SCH-I510 using Tapatalk
 
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