• 1. While the brand specific areas are no doubt great areas to find specific information on your sled and model, these areas usually lack information from members who are very knowledgeably about OTHER sleds, setup, etc. Simply because X-Member who rides a Ski-Doo does not go into the Polaris areas that often and vice versa (When was the last time you Polaris riders went into the Yamaha area? Yamaha riders when was the last time you were in the Cat section?)

    2. I know there will be clutch threads in these brand specific areas and that is fine, but by posting your clutching questions or advice in this clutching area you will be sharing with a much larger audience. So while X-Rider might not ride the same sled as Y-Rider, he might still have some info to share that will help riders of all brands with their setup.

    3. This are will eventually contain everything from how to properly break-in a belt, places that sell clutch parts, a tools section, setups, troubleshooting, rebuild info, spring rates, gearing information, etc, etc.

    Thanks to those who contribute and I hope those that know a lot about clutching jump in and get involved. You know who you are!

    You will also see that there have been other stickies in this area for each major brand. Within these stickies you will find links to other threads and areas that we think have some value. There is troubleshooting, setup, and general help threads in each. Remember to browse the other brands for they will contain tips that can be applied to any brand of clutch.

    Below are a couple of links to two great books that are helpful to those who wish to learn more about clutching. I have read one cover to cover several times and have the other on order.

    Olav Aaen's Clutch Tuning Handbook

    Cutler's Clutch Tuning Handbook

    Currently not available, not sure when it will go back into print

    Also if anyone has anything that needs to be added to this please shoot me a PM!

Clutching theory


Well-known member
Premium Member
Nov 26, 2007
Thunder Bay, ont
Please tell us what you have learned about clutching. Asking questions about theory is OK also.

Keep posts about clutching THEORY not what one setup works with one sled.
Ok you asked for it. :face-icon-small-ton

What I see over the years is three short circuits that cause tuners to being reduced to parts-changers and eventually stumbling onto something that works until someone comes along and out performs them...then they are left in the position to start all over again with more parts trying to find an improvement.

1) Lacking knowledge of the law of how the clutch part works in the system. "Superstitious tuning" to where someone will say "this flyweight works with this helix", "this aggressive curve works with angles in this range", "can't use this spring here or there"
...and it keeps tuners from learning the law of how something works.

The law of how the clutch part works requires that the component exist in some tangible form.
The way the part works in the system can't just be a thought. The part has to be able to be measured and perform an operation that reveals factual data.
Now you have factual data, you'll be able to compile an adequate analysis "by measuring" for your own design or calibrating someone else design.

Flyweight mass determines steady-rpms at full throttle
Flyweight mass determines rpms at steady-part-throttle.
Flyweight determines rpm acceleration
Flyweight curve angle determines rpm acceleration (Comet type)
Ramp curve angle determines rpm acceleration (TRA)
Lever or flyweight Center of gravity distance from crankshaft center determines steady-rpms at full throttle (TRA)&(Comet type)
Lever or flyweight Center of gravity distance from crankshaft center determines rpm acceleration (TRA)&(Comet type)
Spring force determines steady-rpms at full throttle
Spring force determines determines rpm acceleration
Spring "Rate (angle of calculated line)" determines rpm acceleration.
Spring "Rate (angle of calculated line)" determines rpms at steady-part-throttle.
Helix angle determines steady-rpms at full throttle
Helix angle determines rpms at steady-part-throttle
Helix angle determines rpm acceleration
Helix angle determines belt clamp force at "X" sheave position
Final gear ratio determines steady-rpms at full throttle
Final gear ratio determines rpms at steady-part-throttle.
Final gear ratio determines rpm acceleration
Final gear ratio determines angle being used on the ramp (TRA)
Final gear ratio determines angle being used on the flyweight (Comet type)
Final gear ratio determines Lever or flyweight Center of gravity distance from crankshaft center
Final gear ratio determines Helix angle being used
Final gear ratio determines belt position in primary clutch
Final gear ratio determines belt position in secondary clutch

2) Misrepresentation of words communicating in clutching language. Misrepresentation of words and their conduct in a tuning question limits the ability to communicate an observation that can be analyzed. Misrepresentation keeps silent a fact by expressing a belief or a blind obedience to a tradition to which which is in fact not held true.

Example: Many people know my pet-peeve of the word "rate" when talking about springs; the word "force" or "forces" should be used. Force is something you can look at and measure at any instant in time. Rate is something you acutally have to sit down, measure and do some subtraction then division to calculate the "Rate" of a spring. A spring has "rate" in a system, compressed in a distance between two force values. Per inch.

Question – I weigh 230. Do I weigh 230 pressure or do I weigh 230 lbs?
Spring FORCE....force, force not pressure.........230 lbs force! 160 lbs force. 320 lbs force.
I don't weigh 230 pressure. A spring does not have 160 lbs start pressure nor does it have 320 lbs finish pressure.

I try to point tuners to a definition section
so we can all talk the same accurate language.

3) Lacking knowledge of how to measure the parts in the system while it works. (at full throttle) "Measuring" is just as easy to know and use to solve problems however a little bit more lengthy discussion.
Last edited:


Well-known member
Premium Member
Nov 26, 2007
Thunder Bay, ont
Ok another Q for this one:

Spinning 9400 - 9600 with 150/340 spring and 62gr supertips, bearcat seondary with 54/44 and green snopro spring.

Want to get more umph at takeoff and possibly lower the max rpm a little.
Have a 165/310 primary spring. Any bets on the results?

Lever or flyweight Center of gravity distance from crankshaft center determines rpm acceleration (TRA)&(Comet type)
Does the flyweight have composite materials to move around? (nuts/bolts/setcrews)

Do not change the flyweight mass. Keep it at 62g. Take the center of gravity and move it towards the tip. Is there a washer you can take from position # 1 or #2 and move it towards position #3 at the tip?

Moving the center of gravity will allow the engagment to be about the same rpms however the engine will become more revvy in the bottom end/low clutch ratios (adjusts how quick engine rpms will accelerate)
The other feature this will reveal is the flyweight will start to push harder than with the previous center of gravity position. The center of gravity being farther away from the crankshaft centerline, the flyweight will push harder - and you did not have to change the grams.
Oct 8, 2008
On gearing, the lower you are geared the less secondary side pressure is needed due to the decreased load on the secondary.
are you sure about this? if i gear down and puts a lighter spring in the secondary it would upshift even faster, right?
when the secondary seeing less load from the track with a gear down it would upshift faster than before and drop the rpms down.
the right thing to do is go with a stiffer finish rate on the secondary spring or less helix angle.
I dont really understand why people say go with lighter weights or higher finish rate on primary spring, how would the secondary react to that if its already shifting out faster then before? can someone explain that to me:)


Dec 30, 2007
• Use to control upshift
• Shallower angle (smaller number) = faster upshift and slower backshift

isnt the other way, shallower angle= SLOWER upshift and better backshift?
steeper angle= more upshift but slower backshift. Thats why you need a stiffer secondary spring if you choose a steep helix and still wants some backshift left.
Thanks for this; I'll go back and edit in the Clutching Basics thread, I had it that way then changed it. Sorry I suck at life.

Really, but when the combination is done. The steeper helix that need a stiffer spring to work and lighter weights to work. This is what makes most backshift at the end of the day.

A shallow helix backshift better at lunchtime but would overrev, then add primaryweights to get revs down and at the end of the day this has least backshift.

heavy weights/shallow helix = Least backshift

Lightweights/steep helix = most backshift

With the 2ndary springs needed with the helixes to keep tumbs from frying on the sheave.
Feb 12, 2012
washington play grounds
Clutch ratio?

Is there a formula to figure out what your clutch ratio would be? I know how to figure out gear ratios, but the clutch ratio? I'm running a 19-43 gearing(2.26ratio), track is a 162-2"- 3.0 pitch- 8 tooth drivers running about 150 to 160 hp the helix in the secondary clutch is a 36 degree with a red spring for 3000 to 6000ft.
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