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Discussion Starter · #1 ·
What effect do primary spring finish rates have on upper RPM? Is there a rule of thumb? For example if I put a spring in with a finish rate 30# higher is my rpm going increase 300? How much rate will do what?
 

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I have a ratio at work I can post up tomorrow, but I *think* that it winds up being roughly 28 rpm per 1lb of spring rate. So take a 120-290 base spring (for example) and move to a 120-300 spring, that extra 10 lbs of finish rate should net you (roughly) 280rpm. There are a bunch of variables involved, but that should get you close.
 

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Not meaning to dispute what JRider says, he may well have more clutching experience than I, especially on Cats, but I find about 20lbs finish is more like 200-250 rpm diff, or about 10 rpm per lb of tension.
 

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Keep in mind AC springs are rated at less compressed rates than the aftermarket springs.
Example EPI yellow 300#@ 1.2" is softer than a AC yellow/wht 285#@ 1 5/16".
 

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Discussion Starter · #6 ·
Not meaning to dispute what JRider says, he may well have more clutching experience than I, especially on Cats, but I find about 20lbs finish is more like 200-250 rpm diff, or about 10 rpm per lb of tension.[/b]
Your not disputing anything...I just gave an example in my first post. That was a wild ass guess...I have always used primary springs that have finished about the same, but I am trying a spring with about 40# more on the finish rate. Your findings are what I was looking for. Thanks

Is this consistant with with what anybody else has found? Anybody?
 

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Your not disputing anything...I just gave an example in my first post. That was a wild ass guess...I have always used primary springs that have finished about the same, but I am trying a spring with about 40# more on the finish rate. Your findings are what I was looking for. Thanks

Is this consistant with with what anybody else has found? Anybody?[/b]

I dont think polaris prim springs react the same as cat springs. I was using a black cat spring in my primary 158/290 and went to almond/red polaris spring 165/310 and it didnt do anything for rpms. Anyone else experience this?
 

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A little theory to lend to the argument a lower finishing rate is better from a website that I read that made sense....


In this example, increasing the belt squeezing force with a shallower helix and stiffer secondary spring will stop the belt from slipping in the secondary clutch, but also increased the up shift force. There was simply nothing we could do about it because the up shift force is fixed to the belt squeezing force through the sheave angle. This is one of those fixed variables we talked about earlier set by the manufacturers. Remember the 19-degree Secondary sheave angle we talked about earlier? You figure it out.
By trying to fix one problem, we created another. The difference between the up shift forces in the primary and secondary were already coming together at full shift out. Adding the shallower helix and stiffer secondary spring to solve the slippage problem, also creates the potential of actually stopping the clutching from fully shifting out because now the up shift force in the primary starts to match the up shift in the secondary!
Solving this problem lies in the primary clutch. Even though there is sufficient belt squeezing force in the primary clutch at the 1:1 shift ratio, additional up shifting force is needed to offset the increase up shift force due to the shallower helix angle and stiffer secondary spring. Adding more clutch weight or decreasing the top spring load are the two ways to increase primary up shift force. In most cases clutch weight is the right answer, because it takes very little weight to add several hundred pounds of load to the belt.

I have used the Arctic Cat Purple primary spring (Was a one eyed one horned flying purple polaris eater LOL had to throw that in) and made huge top end, although I have never tried them on my Firecat. I have had then on my 2000 ZR 700 and 01 ZR 800. Maybe a project for the weekend...
 

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Discussion Starter · #9 ·
I think that came from SnoTech magazine. I have a spring I would like to try but I am trying to figue out where to start with the weights.
 

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I dont think polaris prim springs react the same as cat springs. I was using a black cat spring in my primary 158/290 and went to almond/red polaris spring 165/310 and it didnt do anything for rpms. Anyone else experience this?[/b]
Yup i know exactly what you mean. Did the exact same thing this year but i had an orange/white 143/290. I did gain about another 100rpm on top tho. But still you would think you would get more than that. Diffrent clutches is what it comes down to. It just brought my revs up alot more out of the hole which is what i was really wanted
 

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I have found about 15#'s is 200 rpms but this depends on the type of tip on the weight. My fave spring for the F7 is CPC purple/white 180/320. Acts like notched weights with out the notch 5000 engagement and rips.

Most of the time 15#'s on top is two grams in weight too. Around 200rpm's or so.[/b]


DonoBBD, I thought the CPC purple/white was a 175/305?
 
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