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Discussion Starter #1
I will first admit that I have a car, not a snowmobile. < g > Though, being an F500, it has a snowmobile engine, and the same primary and secondary Clutches.

I recently was forced to make a half dozen changes to the car at once. And found my primary unable to shift out fully (three weeks ago it did). When marked (magic marker on sheaves), the belt is only climbing half way out of the primary.

AMW 500cc motor, Polaris P-85 clutch (the troublemaker), light blue spring, weights from 51 grams to 46. Hyper Lite secondary, similar to Arctic Cat. 48 degree helix with a yellow ac spring. I geared the car lower, which may have been a cause. Can't change back, went to a wider drive belt. Also rebuilt the primary.

I was also initially getting 400 rpm less than I was a few weeks back. But went to lighter flyweights and then a stiffer primary spring. So I was pulling the rpms, but belt was still not climbing much.

I changed helixes, and secondary springs, to no avail. Then put the old belt on. THEN I put a friend's primary on, with my weights and spring. Same problem! So, am no longer confident that a new primary is the sure solution, though that seems the next step.

Any ideas?
 

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I'm sorry I cant help out,... actually didn't even know wtf an F500 was, til i did a search. Awesome lookin machines. If anyone else was as clueless as me here's a couple of pics @ the bottom of this page.
http://www.geocities.com/bcbackwoods/About.htm
 

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Discussion Starter #4
I race it, baby! < g > Not many places to drive a car with an inch and a half ground clearance. This is a car that you snug down into. It is sized for me, and larger folks just can't squeeze in. Steering wheel must be taken off to get in or out 600 pounds plus me, tires - racing slicks - wider than on most cars. A real blast to drive.

Still thinking of my problem getting the primary clutch to shift out. I was making rpms, so my friend's primary clutch should have shifted out. Research on the net shows nothing here. Aaens book (the clutch tuning bible) does not mention it.

My car is actually very similar to the pic on the right at the bottom of the page, on the mentioned sample.
 

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Would this help, or have you been through this whole webpage already???

http://www.f500.org/tech/clutch_tuning.htm

or back one: http://www.f500.org/f500_tech.htm
 

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I am very familiar with P-85 clutches, but i am curious what kind of horsepower does one of those engines make???
 

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Discussion Starter #7
Yes, one of my primary hangouts is the f500 site, and all its technical jargon. This document, plus the Aaen book (the clutch bible), plus all my net research have yet to find anyone who has experienced this problem.

One hint, though, that if the spider bolt wasn't tight enough, this might happen. I watched the guy grunt my nut back on when he rebuilt it. I suspect that this means that this coming Saturday I should have the guy disassemble then reassemble the clutch again. Competition Sunday.

My AMW (2 Stroke International, now) motor is 2 cylinders, 2 stroke, roughly 86 HP.
 

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I'm thinking your primary is fine, but the changes you made have made your problem worse; notably...

I was also initially getting 400 rpm less than I was a few weeks back. But went to lighter flyweights and then a stiffer primary spring. So I was pulling the rpms, but belt was still not climbing much.

By putting lighter weights on and a stronger spring you are not getting enough force generated to drive out your primary all the way. So believe you need to increase your weights. The stiffer primary will push out your engagment rpm and this will have some impact on it shifting out too I believe.

I'm no expert here but that is what the physics should dictate. Hope that helps.
 

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Try taking some spring pressure off the secondary clutch. It will allow the belt to pull in easier and ride higher in the primary.
 

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man I want one of those,looks fun!!make sure both clutches are clean, polish the helix to help make it shift faster..otherwise im not sure what the problem is..
 

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You may want to take your belt off to see if the primary will open up all the way. This way you can rule out any 2ndary issues if it won't open up. Then I'd look at the weights and primary spring per my earlier comments. Good luck.
 
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