My clutching handbook is on the way (from Aaen) but I think we agree on some aspects of it. I will have to look up in the book (when it comes) if we are right. Here is my best guess, from what experiences I had.

Changing the primary clutch spring/weights has the most effect on initial engagement and acceleration, at least up to a point. Of course you can put in such a tight spring that it will never shift out, but within reason I think it mostly affects when the clutch grabs & how fast it upshifts from the start.

The secondary clutch will have more effect the more the tranny shifts up. The action between the spring and helix is what keeps the transmission from just shifting into high (so to speak) and staying there. The more pressure the spring has, the more RPMs the engine will run at a given speed/load combination. Again, I think the higher the tranny is shifted out, the more the rear clutch affects this. Too little tension, and it will bog the engine before downshifting, too much, and the engine will run faster than optimum RPM. The trick is to find the proper balance between the two. I think that is why a full clutch kit is more effective than just changing springs, especially if any mods are done to the engine.
These are just my opinions, but:

If you put a pipe or reeds on a 2 cycle (or open up the airbox/muffler flow on the 4 cycle) you will get more power at a higher RPM. This would benefit from the white/green primary spring (to let the engine rev more before clutch engagement) and also tightening the rear clutch spring (to better utilize the increased HP at higher revs).

Just imagine how much R&D was involved to get them to work as well as they do! Especially considering how truly simple the CVT transmissions are mechanically.

 

When I was at my local Polaris dealer the other day, I noticed that they had the snowmobile tune up charts on the wall.

The charts include information on how to set up the machine based upon temperature, altitude and rider weight. There were suggestions for jets, suspension, springs and clutch tuning. I asked the tech if charts like that were available for ATVs and he said "Oh yeah, they are in the front of the respective service manual, we just haven't put them up."

Tom said that the charts were very refined and offered excellent tuning aids for the shop. He said that all they did was set the jetting by the charts in the National Weather Service and the suspension and clutching by rider weight. 90% of the time he said that was all they had to do. I should have bugged them to get out the chart for the ATVs!

I'm sure that a 135# rider and a 325# rider could both benefit from some clutch fine tuning. The tech said that the average machine is set up for a 180# load.

 

Hehe... Nothing like replying to my post 3 months later . After taking both clutches apart and inspecting them, replacing the belt and looking it all over real well I ended up taking it to my dealer. This was back in Feb. They couldn't find the problem either so I figured I would suffer with it till it broke. Well, after 3 days at Hatfield McCoy I did a complete service and drained the starter and recoil drains. When I pulled the plugs oil ran out. I pulled the countershaft dipstick and it was REAL low. Pulled the recoil starter out and the cord was soaked with oil. I took it in to get the seal replaced and while they were working on it they found the shaft that holds the front sprocket on would move up and down a lot. So that bushing is out of it. They are replacing it and I hope that fixes the chattering. It makes sence that would be the cause. I should get it back sometime this week. I just hope the bushing didn't tear up the shaft after riding it all this time with a problem.