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Clutching

Custom Clutching Setup

Clutching is the most important and most overlooked part of you snowmobile. Its the key for transfering power from the engine to the track.

I ask each buyer about rider weight, altitude, motor, output and other variables so I can supply a complete clutch kit that will work best for the individual customer’s sled. The primary clutch (drive) controls engine RPM, the secondary clutch (driven) controls up shift acceleration and back shift, keeping track speed high.We also prefer to run multi-angle billet helixes with custom angles matched to each customer’s sled.

Clutch Tips

Tightening Steps:

a) Initial tightening to 88 ft-lb b) Loosen the bolt and re-tighten the bolt to 44 ft-lb Clutch alignment center to center 267 mm 15-17mm off-set. Clutch Alignment: Your goal is to: a) Get the drive belt to the top of the secondary sheaves on the driven clutch. (Adjust belt height). b) Belt must run in center of drive clutch. c) How do I do this? You must move motor with motor mounts bolts loose. Don’t forget motor torque stop. Also, shim driven clutch In or Out. Always use new drive belt for proper set-up.

Clutch Tips:

Periodically clean clutches. Break cleaner works well. Put a towel in the belly pan to pick up mess. “Hot Tip for Carlisle wash your drive belt in hot water and soap, 409, Simple Green, etc. Also, use a brush to scrub sides clean. Let it dry. It will work better and last much longer. Less slipping, less heat, more acceleration. (NOTE: Late model clutches use special bushing that needs NO LUBE).

Clutch Tuning

This is the most difficult part of your snowmobile and the most overlooked. The “Rule of Thumb” is, if you want to change the engine RPM for engagement or shift, work on the Primary clutch. If you want to improve upshift or backshift, work on the Secondary clutch. (High efficiency is “Free Horsepower”). NOTE: We have had a large number of YVXC Clutches Blow-up. Please inspect your primary clutch sheaves for heat cracks from the center, working outward. I feel the cracks are from very high heat due to all the belt slipping.

Belts

The Yamaha 8DN belt is very hard and has a high amount of slipping, which will create heat and loss of acceleration. (The only “good” thing, is that it will last forever). Harder is not better for performance. We use a Carlisle Ultimax that is softer, this enabling us to get the drive belt to the top of the Secondary Sheaves on the driven clutch. Carlisle has a one year warranty. Buy “two” and you have a lifetime supply of belts. Read the back of the belt sleeve, less slipping is “Free Horsepower”.

Carlisle Ultimax XS-805

Last’s 40% longer than any other belt tested. More races are won on Carlisle belts than any other belt. 8 out of 10 riders use Carlisle belts. Ultimax XS-805 reduces cord pop out and wears better.

For big horsepower sleds we recommend the Carlisle XS-805,

 

New Secondary Clutch Shim Kit

This kit will adjust your belt height to the top of the secondary clutch sheaves which gives you a lower ratio upon engagement, and that translates to better acceleration it also eliminates clutch drag when the sheaves close. $25.00

 

 

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Is Clutching Magic?

Is Clutching Magic? Not really! First draw a large pentagram on the floor around your sled, get some candles and a virgin to sacrifice, no-no that would be a waste. Anyway, Olav Aaen’s Clutch Tuning Handbook is the bible of clutch set-up. If you don’t already have a copy, get one, read it, put it under your pillow at night, take it to the can with you, read it, read it, read it.

Even though the clutches appear to be pretty simple, they can make a perfectly sane man sound like a babbling idiot, muttering things to himself like, wait a minute I added weight and….No, if I increase the spring rate and…..No if I…. DAMNIT !!!!! The basic idea of clutch tuning is to get the springs and flyweights in your primary (drive) clutch to bring the engine to a specific rpm PEAK using different weight and spring combinations. These combinations are endless that’s why no one person has all the answers for every condition.

Then adjust the spring tension and helix ramp angles on the secondary (driven) clutch to get the shift-out you want. These combinations are also endless. The shift “characteristic” is dependent on your personal preference and riding style. The theoretical “ideal” is a slight over peak at engagement, then flat at the peak HP out all the way though the shift-out with the rpm slowly climbing above the peak HP once you’re shifted all the way out into overdrive .75:1. Remember that’s theoretical. The point of this being that generalizing clutch settings is impossible.

Even if I tell you exactly what I run in my sled, it’s no guarantee it will work for you. Most tuners won’t give away their “trick” clutch setups that cost them dearly in lost hours of sleep, endless parts runs and tuning rides, but they may be able to point you in the right direction. Clutch tuning is the one area where you can gain a competitive advantage.

Where do I start? Focus on the primary and getting your engine rpm right. That means right at PEAK HP with steady acceleration. You’ll increase or decrease the weight and or profile (where the weight is distributed in the weight itself: heel, mid, tip) of the flyweights to achieve this. Lighter weights raises the rpm heavier weights lower it. Heel = bottom end, Middle = Mid-range, and Tip = top end. Make sure you’re using the same profile of weight when you make changes or you’ll end up chasing your tail. Do NOT change the secondary to adjust engine rpm.

I’ve seen too many people increase the pre-tension on their secondary to bring up their engine rpm, myself included. You are shooting yourself in the foot !!!! It decreases the efficiency of transmission of power to the track while adversely affecting the ability of the secondary to keep the shift curve flat. Once you have your rpm where you want it, you next job is to get it to shift out the way you want. That’s the job of the secondary. The combination of spring and helix is what determines this. Multi-angle is what I prefer. The secondary spring directly equates to side-force on the belt.

The idea is that the more side-force you have on the belt, the less efficient it is because of belt drag. Secondary pre-tension (wind) should be around 16-24ftlbs. What I try to do is get to the minimum side-force possible without slipping the belt in the secondary. Too much side-force and the clutch will back-shift too fast and put you in too low of a ratio and over rev when you stab the throttle out of a corner. Too little and it won’t back-shift fast enough and it will react sluggishly (bog) and you’ll loose rpm climbing hills or trying to maintain high speeds.

Lastly, I’m a believer in low gearing, its less work for the clutches and engine they will run cooler. Most sled heads don’t realize that the factory gears sleds for speeds higher that the sled will ever reach. They never reach a true .75:1 ratio, also the track and engine combinations the owners and after-marketers add, won’t allow the motor to pull the tall gearing (pulls the rpm down on a long climb or high speed).

Common Pit-Falls: Clutches MUST be clean. Bushings MUST be serviceable. Springs MUST be replaced annually. Belt MUST be cleaned before break-in and every other ride (preferably) and within minimum width tolerance. If all of the following are complied with, see below. Only change ONE thing at a time. Take good notes, like snow condition, temp, elevation, terrain, what you changed and the effect it had. The primary (drive) and the secondary (driven) will directly effect each other, try not to over compensate one to “fix” the other, it’s a BALANCE you’re looking for.

Note: Remember, what works for boondocking will not work for drag racing and vise versa.

Under target rpm.
1. Too heavy primary (drive) weights.
2. Too steep secondary (driven) helix angle.
3. Too low tension in secondary (driven) clutch.
4. Too tall gearing.

Over target rpm.
1. Too light of primary (drive) weights.
2. Too high tension in secondary (driven) clutch.
3. Too shallow secondary (driven) helix angle.
4. Too low gearing.

 

Custom Clutch setup for Turbo and Supercharger

I ask each buyer about rider weight, altitude, motor, output and other variables so I can supply a complete clutch kit that will work best for the individual customer’s sled. The primary clutch (drive) controls engine RPM, the secondary clutch (driven) controls up shift acceleration and back shift, keeping track speed high. We also prefer to run multi-angle billet helixes with custom angles matched to each customer’s sled.

Nytro, Apex, RX-1 Dalton Adjustable Weights for Turbos and S/C.  $195.00

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Clutching

A Polaris primary on a Yamaha? We offer the very tunable and reliable balanced 30 degree taper P-85 type primary clutch for the triple Yamaha’s at $435.00. This comes complete with adjustable weights and spring.  After years testing shows less belt wear, and improved contact from sheave to belt which means more power to the snow where you want it.

We also have Yamaha YVXC Primary clutch kits setup to the riding style you request for $195.00. For the Yamaha secondary we have Billet Helixes and the new for 2003 “Stealth Helix” also $170.00

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Clutch Kit

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Custom Helixes

“High efficiency is free horsepower” Our custom helixes are cut to exacting tolerances to meet your needs, and set the standard in the aftermarket industry. Price $170.00.

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updated 7/26/2016