JavaScript seems to be disabled in your browser. You must have JavaScript enabled in your browser to utilize the functionality of this website. Here are some general clutching rules you should play by! Adding horsepower normally means you need to add clutch weight, go steeper on the helix angle, or both. Most small modifications only require adding clutch weight while larger horsepower modifications will require you to change both.

Not changing clutching when you add horsepower will result in over-revving. On some 2-stroke snowmobiles you must add clutch weight or RPM will be too low. If you do not load the motor hard enough, not enough heat will be built up in the pipe which will result in poor running condition and lower than normal peak RPM. This is about the only case when low RPM is seen that weight should be added. Tech Videos for clutching:.

My Cart 0 Shopping Cart. Search Search:. This needs to be in your model's peak powerband for best results. Register your email for news and special offers. Community Poll. How did you hear about us? Sign up for exclusive offers. We are here to help.Log in or Sign up. We are no longer supporting TapaTalk as a mobile app for our sites. The TapaTalk App has many issues with speed on our server as well as security holes that leave us vulnerable to attacks and spammers.

Messages: Location: MN Flatland. I have a 09' Nytro MTX that is stock. My question is what is everyone else running for weights? The guy I bought it from ran the stock weights up to he claimed 10,' West Yellowstone. The manual says to run the 8FS with no rivets 8 - 10,'.

He also gave me a set of HeelClickers weights and springs. A set up for Sea level and Ele. He said he never ran the HeelClickers at Ele. So they are not set up. I don't want to have to screw around when I am out west just plug-n-play. Your thoughts are greatly appreciated.

Ok so does anybody know the weight of a 8FS with no rivets? Messages: 1, Location: AK. Buy This. Messages: Location: Minneapolis, Minnesota. Messages: 33 Location: Sheboygan, WI. I have a stock nytro mtx with the sea level gearing and a slip on yosh pipe. If I'm hitting the rev limiter taking off from a stop but not at top end, are clutch weights, power commander, or is different gearing the way to go?COM Enter keywords or a search phrase below: Search.

American Snowmobiler Gear. American Snowmobiler Back Issues. American Snowmobiler Calendar. Login or Register Customer Service.

By Olav Aaen November 20, Today's primary clutches are easily divided into two categories; those that use flyweights with a curvature working against a roller, or those with an arm with a roller attached to it working against a curved stationary cam.

In this story we'll look at the first category. Primary history The industry took awhile to settle on these two configurations. Early primaries often had simple weight blocks or even garter springs sliding against outside covers. This extremely high friction condition worked adequately when snowmobiles used small industrial engines with wide power bands. As engines improved and power increased the whole belt transmission came under sharp scrutiny.

Kidney weight flyweights were the next development, and had the advantage of being tunable by adding bolts, washers, and nuts, but a tunable curvature to calibrate the belt force was limited with this design. The moveable sheave on most of the early clutches also ran on a spline on the shaft, and this resulted in high friction as the torque load was high at the small radius. When Polaris and Comet came out with newer designs in the late s, they had two big advantages.

First, the torque transfer point was moved away from the spline on the shaft and out to plastic buttons mounted on the spider. The new flyweight system consisted of curved weights acting against rollers mounted on the spider. By controlling the mass and curvature, the shift force could be matched to the engine power curve.

This system with a number of updates and refinements is now used by Polaris, Arctic, Yamaha and Comet. They all use a curved flyweight pushing against a roller and torque transfer points on the outer perimeters.

The force balance working through the moveable sheave and shifting the belt through the ratios is complicated, and the present flyweight systems have evolved to meet these very special conditions. When the belt starts out in a low ratio, the engine's torque is tripled at the secondary shaft. This requires high side pressure on the belt to transfer the power without slippage. To match these side force requirements, the primary sheave needs to push against the belt many times harder in a low ratio than when the transmission is in overdrive.

This is accomplished in two ways. First the flyweight pushes against a primary spring. As the transmission moves into the higher ratio, the spring force gets stronger depending on the spring rate, and this force is subtracted from the flyweight force.

The centrifugal force acting on the flyweights is transferred into horizontal shift force through the interaction of the flyweight curvature with the stationary roller mounted on the spider.

The contact angle in the horizontal plane determines the amount of force acting on the moveable sheave through the flyweight pivot pin mounting in the sheave itself. The present flyweight configuration is well suited to this purpose. The flyweights start out hanging down in a vertical 6 o'clock position and this gives it a large horizontal force component with respect to the roller.

Adjustable CVT Primary Clutch Weights for UTV and Snowmobile tutorial

As the flyweight swings out when the transmission shifts into higher ratios, it moves toward an 8 o'clock position. Due to its decreasing angle to the horizontal plane, the shift force on the belt is reduced, just as needed. A flyweight has three distinct phases, the engagement area Athe transition area B and the shift curve C. Centrifugal force F is determined by the weight of the flyweight Mthe radius of the center of gravity from the center line of rotation Rand the square of the speed of rotation V.

Clutching forces examined By now this whole force component picture confuses most people, because we are not used to thinking in terms of diminishing forces in order to shift out into a higher ratio. Intuition would try to convince you that an increasing force would be needed to shift the belt into a higher ratio.

This was the case when we only had a pressure spring to control the belt pressure in the secondary, but with the introduction of torque sensing helixes the whole picture changed.This page may take a while to load.

Stick around because it's worth the wait.

Clutch Weight Question

Thanks Authorized Distributor. For tech info on other Heel Clicker kits click here. As we all know, clutching is a very complicated subject. As an engineer I always look for evidence that supports a complete theory of clutching. What has always worked for me is using computer simulation to give direction in which way a mechanical system will behave. Often, simply removing preconceived notions from my way of thinking can result in true knowledge gained. This has been my experience many times, what I thought was true, was not!

When you have an end result in mind before you start a project you rarely come up with the right answer. Figure 1. Clutching is one of those high emotional areas of snowmobiling. Pipes and porting also draw lively conversation, and I think its all for the same reason.

Clutching - Light or Heavy Primary Spring Best

Most high performance snowmobiles want to go fast. As fast as the limitations of the engine size will let them. There is nothing like getting your cc sled to out run an in a ft. This article deals with one of the most asked questions in all of high performance snowmobiling. Savvy tuners realize that working with several different clutching components can give similar end results on the tachometer. For example, putting in lighter flyweights gives similar results on the tachometer as putting in a shallower helix.

But one set-up is faster than the other, so is just reading the tach the right answer? Which clutch should I work on, and why? These are some of the most asked questions in all high performance snowmobiling. This article uses computer simulation to try to answer some of those questions. Many man hours of programming and engineering are represented in the following pages.

It is simple to assemble, cheap to build, and it is very efficient in power transfer when properly calibrated. Chances are they will be around for a while. Overall CVT clutch efficiency is based on several major factors, but as we will see tuners have control over just a few of them. These losses are due to engineering compromises that always occur when designing an entire power train package. Product cost, standardization in tooling, and environmental issues are all things that have to be considered when designing any product.

In a CVT transmission, standardization in tooling seams to be the driving force of many engineering decisions. All four major snowmobile manufacturers use the same clutch on a variety of different machines. For example, Polaris uses its P clutch on 35 hp cc fan cooled machines all the way up to the XCR making hp. It is the fixed variables an oxymoron that are basically cast into the design.

how snowmobile clutch weights work

Things like center hub diameter, sheave face angles, outside diameters, contact patch area, and material choices. These are just a few major design considerations that greatly affect CVT clutch efficiency.

Designing a CVT clutch system around 35hp rpm instead of hp rpm will result in a lot of compromises.

how snowmobile clutch weights work

All manufacturers have this same problem; how to achieve the best overall performance for a variety of different engines and sled designs.Clutching For Power by: Yamyrider. Sled running like a pooch? Last fall I had an interesting discussion with a friend of mine — a long-time snowmobiler who is brand loyal to his blue machines. His were fast, but he was tired of getting smoked by smaller-displacement sleds. He wanted his sled to be trail able. I convinced him to try dialing-in the clutching instead.

We took his sled to an open field we use for testing and set up timing lights. We tried many combinations of weights, springs and helixes. A cc triple that was getting beaten by cc twins was now running faster than an cc twin at the foot mark.

The interesting thing is, most people — even veteran snowmobilers like my friend — would never guess how radical a change clutching adjustments can make. How is this possible? A snowmobile has two clutches: a primary, or drive clutch; and a secondary, or driven clutch. A ribbed rubber belt connects them. The primary clutch consists of a stationary sheave, a moveable sheave, a spider assembl ya spring, three or four in some cases cam arms, and a cover.

The secondary clutch consists of a stationary sheave, a moveable sheave, a spring, a helix and a retainer plate.

The primary clutch bolts directly to the crankshaft of the motor. Whenever the motor is running, the primary clutch is spinning.

The secondary clutch connects to the jackshaft of the snowmobile. It only spins when the primary clutch begins to shift out and grabs the belt. Both clutches move two ways. They spin on their respective shafts and they slide in and out.

At idle, the belt is at the bottom of the sheaves on the primary clutch. As rpm increases, the primary clutch senses torque input from the motor. At a certain rpm, it will turn fast enough that the cam arms will begin to move and overcome the pressure of the spring in the primary. When this happens, the moveable sheave slides in on the shaft of the fixed sheave, thereby pinching the belt and causing it to spin the secondary clutch.Forums New posts Search forums.

Media New media New comments Search media. Search Everywhere Threads This forum This thread. Search titles only. Search Advanced search…. Everywhere Threads This forum This thread.

Search Advanced…. Log in. What's new. Thread starter Frostbite Start date Nov 10, JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. Frostbite Well-known member. Lifetime Membership. Dec 15, 4, Eastern Washington.

I was always taught to "load the motor" as I learned snowmobile clutching. That meant to make the engine work struggle possibly to pull shift speed RPM. I did this with great success on my past sleds. To add another factor to the primary clutching equation, I found that using the highest total force spring available allowed me to throw more weight through my clutch weights at my primary clutch and engine.

how snowmobile clutch weights work

This of course made the engine work even harder to pull top RPM because my primary weights had to be very heavy to keep from over reving with high total force springs. I ended up sticking with the highest total force primary spring available and used it as a constant. I also learned a couple of things when I started playing around with clutch weights. Heavy clutch weights seem to make the sled less snappy rightfully so because the engine has to work so hard to overcome all that weight.

Lighter clutch weights seem to make my sleds feel much more snappy and dirt bike like. Heavy clutch weights that can be pulled easily by a sled at lower elevations become insurmountable for the engine to pull as the elevation increases.

My question is: Is a sled able to reach it's full power potential when a primary spring of less than high total force is used? If a lower total force spring is used, lighter weights consequently have to be used and the motor isn't being loaded as hard as it could be if one was using a higher total force primary spring. If I apply the above theory, I could theoretically throw more weight at the primary and load the motor harder potentially pulling a few more horsepower out of the motor if I used the higher total force spring.

What do you guys think? Arctic Thunder Well-known member. Dec 7, 2, Lewiston, Idaho. I always looked at it as a balancing act. Either heavy weights, stiff spring or light weights light spring. IMO I like the snappy feel. So I prefer the lighter weights and lighter finish rate spring. Also I always felt there was a lot more clutch wear with the heavy weights, so again I tried to stay with lighter weights. Just my opinion.

Probably left a lot on the table in this area. Again this is an opinion. I think drag racers like the heavy weights.Making changes to the clutch that seem insignificant can have huge consequences to horsepower, torque, and belt life. Hang with me for a minute here. Most cars shift through different gears as you accelerate. That means it can stay in the optimal RPM range all the way until you hit the mechanical limitations of the clutch.

But the mechanics that go into that process are a little more complicated. The primary clutch looks kind of like a couple dinner plates smashed together with some extra hardware on the backside of one. When your foot is off the gas, the clutch is fully open because the primary clutch spring holds it open. As soon as you touch the gas, the RPMs rise and the clutch starts to close.

This makes the two sheaves move closer together and pinch the belt. That pinch is what starts driving the belt and driving the rest of the machine.

This is where the magic happens. As the sheaves move closer together, the belt moves further out on the clutch, like a chain on a bike moving to larger gears. Except, because the clutch is CVT, that change is smooth. This is where your clutch arms and clutch springs come in.

The primary clutch spring is trying to keep your clutch open with all its might. The clutch arms fight against the spring by using centrifugal force to try to close the sheaves.

Clutch arms at different weights change the rate that these sheaves close. There are lots of little details that make this run smoothly like the material used in the rollers that arms push against, the bushing in those rollers, the bushings in the arms that allows them to pivot, and the machined curve of the top of the arm.

Polaris gets those details right so all that matters after that is spring rate and arm weight.

how snowmobile clutch weights work

When we make a clutch kit for Polaris vehicles, all we do to the primary clutch is change the spring out for a harder or softer spring and change the clutch arms out for a different weight.