Thor and Jack, I am in complete awe! You guys are awesome. Maybe you b.s'ed your way through those posts, but I think NOT. If either of you start a school on clutching, count this dumb ole okie in. HOW besides reading about clutching did you guys get this knowledge? Experience? On hands learning? Let me know when yalls book comes out! Thanks for blowing my mind.

Thor, I just read some of your replies on another forum. Are you in the quad business? You really know alot about Polaris'. I am not trying to pump daisy's up your rear, but you know what your talking about. One more thing Thor, what is a gold secondary spring good for? Like I have typed before on other topics, the mech. put in other "parts" other than a stock HPD kit. So I really dont know what I have. Any suggestions? I know a stiff primary spring will make it engage high, but will it also make it "hit" hard when it does?

 

This is how it goes, I think
cvt clutches work by sensing load as belt pressure. When the primary makes more belt pressure than the secondary makes they will UP SHIFT. When the secondary makes more belt pressure than the primary they will downshift. When you mash the throttle the primary ENGAGES and the clutch grabs the belt. Once it has created enough force to overcome the primary spring, secondary spring and the resistance from the helix it starts to SHIFT OUT. This shifting continues until the belt has come to the top of the primary and top speed occurs. When you let out of the throttle the clutches BACK SHIFT or return to lower gear. This also occurs when the clutches sense (through the helix) a greater load on the machine. This is the clutch dance your bike does like a thousand times an hour or more so that you are always in the right gear and always have good power.
The parts that control this shifting are: primary spring, weights, rollers, secondary spring, and helix. There are a lot of minor things that also effect performance but for today we will assume that all is well with your system.
For the best acceleration it is necessary to get the motor up to its optimum rpms and keep it there. It is also necessary to make the bike start out with as much power as possible with out loosing traction (which is never a constant)
Always remember that more force means less rpms and more belt squeeze.
Changeable parts of the clutch and what they control are:
* Primary spring: controls the force created by the weights pushing against the rollers. The higher the tension the higher the rpms. Higher pretension gives you higher engagement and higher rpms through the initial shift out. The higher the end tension is the higher the rpms are when shifted out all the way.
* Clutch weights: create centrifugal force to squeeze the belt. The flatter the curve on the contact surface the slower the up shift force. Also the steeper the angle of the ramp in front of the roller will decrease force (this is called notching and is used for engagement issues) Weight is also a factor, more weight means more force. More weight at the heel gives more force at the beginning of shift out. Heavier tip gives more force at the end of shift out.
*Rollers: some clutches have different size rollers. Smaller rollers increase force. Larger ones decrease force. This does so across the entire shift curve.

*Secondary spring: in most clutches this spring has two function. One is to give side force to the belt. More side pressure at the beginning of shift out causes a slower shift out. A higher pressure at full shift out can cause the clutch to not shift out all the way. The optimal spring is one that is as week as possible without causing the belt to slip. The other is to give twist pressure against the helix to adjust shift speed somewhat. The more you twist the spring the more friction there is on the contact points of the helix. This causes the secondary to resist shifting out as fast. This is also why it is less effective when using rollers. The roller has no friction so more pressures on its contact point does little?
*Helix: this is essentially a wedge. It senses the load and makes the clutch resist shifting out when there is more loads. Higher angle helixes shift out fast, back shift slower, and give less belt pressure. Compound helixes try to give the best of both worlds letting the clutch shift out fast at first when little belt squeeze is needed then as the contact points on the belt get smaller and the need to have more belt squeeze increases the helix has a lower angle.
This is the dance as simply put as I can. You can read all of these posts and you will be ready to start selling clutch kits. Wrong. If you really want to understand how it works then you need to read every dam thing you can get your hand on and then start buying parts. Start with others clutch kits and tune from there for a few years before you start from scratch. It can be expensive. Don’t buy a kit that is not adjustable. They are a rip off and are hard to tune (usually cheaper) buy thunder weights or heel clicker. Then you can adjust your rpms to your bike power. That reminds me, you need a tach. A snow sled tach will work; atvs are 6 pulse just like sleds if you run your headlights (output drops to 3pulse from 6 when battery is full). Have it checked to make sure it is accurate. Connect to the yellow wire with the red stripe coming out of regulator box. Do not use a digital tach to do clutch tuning, as they are hard to read rpm highs and lows.

Got to go. Good luck.
I’m sure I have forgotten something. Just ask, as I will be on the site regular now, as snow is melting.

BETHEVIPER
scott

 

You guys blow my mind!

 

Holy mechanical engineering majors Batman!

 

Speaking only about the weight, much has to do with the central mass in relation to the pivot point. You can vary the central mass by shifting it to different area's of the weight which will help with keeping the rpm at peak hp output from the beginning through full upshift. This is the ultimate goal, an accurate tach is a must plus you must know the hp and torque curve of the motor your dealing with. I would be very hesitant to notch the weights for higher engagement if your doing other than drag racing. The aggressive engagement gets old if you trail ride. You can tuck the weight back under the pivot point to help this. I would warn you to be careful modifying weights, they all need to stay identical in weight to keep your balance correct and you don't want to weaken them to the point of failure as that plastic cover will not confine them if they break. Also the spider spacing needs to be correct. You will only learn by experimenting with your set-up, use a dragstrip and time your runs which will help with what works and what doesn't or have the motor dyno'd at the crank if possible so you know where your optimum set-up needs to be. Good luck.....

 

While you guys are writing books on it I'll just take my quad to the dealer for clutch work. Meanwhile I'll try to decifer what all you guys were trying to explain when I have a free day.

 

dude you took my head, give it back.
forgot to mention that when you are ready to test i cant stress enough you need to keep notes and only change one thing at a time. i do all my atv testing with cover off(not safe but way faster. measure every springs installed weight and compressed weight befor you start. make or buy some shims to install behind the springs to increase rate(.030 thick are a good size)dont add too many in a setup you can coil bind. these come in handy whe you need just a 100 or 2 rpm or when the springs get older.
have fun, clutch tuning is the most fun you can have being that frustrated

 

I can honestly say I have learned alot since I first posted this topic. Its nice to look back and realize what I've learned. I may just actually be getting smarter. LOL

 

Here is an oldy. Have to do some clutching on 2 500.