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Discussion Starter #1
I just installed a P85 on a 97 Yam 600SX(twin)and would like to know best way to go from here.
-Stock motor and gears
-Stock secondary setup.
-added a 136 rear skid and 1.25 track.

The stock Yam clutch would engage at ~3400 and top out at 7800(@90MPH), supposed to engage at 4200 and top 7900 so assumed primary spring was pooched(stock weights and rivets)

P85
- engaged at ~42-4500 which is where it is supposed to be.
-I never pushed the top,it hit 8500(@65MPH) and shut I it down before it broke
-pol oange primary(70/199)
-Pol #10 weights(51.5 gr.)
-not new belt but nicely broke in
-Alignment and offset on the mark
-Will be used for trails and ditches/fields

Do I go with a lighter finish on the spring to bring top end down?
Do I go with heavier weights with more tip mass?

Dont want to spend too much on weights as a thundershift kit is on the way but may not get it before we leave for Christmas.(with the sleds of course)

Sled was a gas pig before so it would be nice if it improved some.

Sorry for the long post but tried to be thorough.
 

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What I would do is look at loading down the weights. Unfortunately if you do not know where your current setup is peaking out at, it is going to be hard to say how much too ad.

If you are looking for adjustable weights, I would also consider the SuperTips weights. They are more adjustable and you have a wider range of adjustment.

As far as dialing in a P-85 on a Yamaha, consider talking to Holtzman. They probably have a starting setup to get you in the ball park.

You definately need some weight to drop the RPM thought. I am guessing you will end up somewhere between 58-62gr using the #10 Polaris weights

I would stick with the #10 profile though, they are probably the best ramp profile for trail riding. I have used them extensively in all of my Polaris and Cat clutch kits. Best upshift and back shift you will find in a flyweight. They are mid-heavy.
 

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Discussion Starter #3
Thanks, I talked to Tom Hartman(super nice guy, very helpful) and this is what he figured for a starting point. I guess that they don't do too much with the twins any more so it was a bit of a guess. These motors are not very powerful so I expect a dramatic drop off in top end rpm when I get close to the right weight. Would a spring with a lower finishing force help any? It is pretty responsive now and free rolling once you get out of the gas. The old clutch acted like an engine brake.

Dwight
 

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Dropping finish tension will drop RPM, but it will also gradually drop the RPM from engagment to full shift also. The farther from engagement the more it will drop RPM.

For most applications you want to run as stiff of a spring as you can, then throw as much weight as you can at it to slow it down.

I think you are in the ballpark, and yes the adjustable weights are pricey, but you can find used Polaris weights on ebay and such too.
 

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You can achieve very similar resutls with many different combinations of parts. You can maintain the same peak rpm with stiffer springs and heavier weights, or you can use lighter springs and lighter weights, with pros and cons to each.

There is a meausrement of a spring that is kind of hard to measure, but what it is called is "rate". It is the relationship between the engagment tension and full shift tension.

Example: The famous AC "Orange/White" spring (440 SnoPro Race setup)

It has 143lbs at engagment, 290lbs at full shift

290-143 = 147 lbs of "rate", or 147lbs of change from engagment to shift

Another common one, Goodwin Black 180/330 = 150lbs of "rate"

You can have two setups for each to net the same results, my example is in a ZR800

With a Goodwin Black, you need 74gr polaris weights to get the right RPM on that sled, about 7700RPM

With the SnoPro spring, you need only 70gr weights to get it to run that many RPM

So what is the difference?

Well, first off engagment. With the GP black, it engages about 4700. The snopro, about 4200. That is a big change depending on the riding you are doing. A sno/cross guy would like the black and a mountain guy would like the snopro

Second, this value known as "rate" will change how the sled "feels" (best word I can use to describe). This is commonly conffused with backshifting.

When you go into a corner, come off the gas to the point of the clutching needing to backshift, then you get back into it, you are not going to be at peak RPM, it is going to drop. How much it drops depends on the "rate".

Rule of thumb here: The closer engagment and finish lbs are on a spring, the less rate there will be, and this tends to be more "revvy" when on and off the gas. The farther away they are, the less responsive the setup will feel.

Kind of like a motorcycle riding at a steady RPM in a gear. If you are going 40mph in 3rd gear and snap on and off the gas, it will feel much less responsive than if you are in 1st gear.

The use the biggest spring you can theroy was a good starting point that I was given years ago when trying to clutch a machine that you had no idea on how to clutch it. Start with your biggest spring and heaviest weights and go down on both from there.
 
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