There are 4 ways to accomplish more top end.
1. Primary clutch spring with a higher spring rate
2. Primary weights with a less aggressive curvature
3. Secondary spring with a higher rate but same pretension
4. Less Helix angle.
I was reading up on this last weekend since I am adding a set of Heavy Hitters to my sled this season. I'm not that smart just what the Aaen clutch tuning handbook said.
The Helix is the round object in the middle of your Secondary / Driven Clutch. They come in many different angles or a combination of Angles.
To change the spring rate you will need a different spring. The rate is determined by the wire diameter and how long it is along with how much pretension is built in.
I would highly recommend picking up a clutch tuning book like Olav Aaen's, its only about 75 pages and does a real good job of describing the basics of clutching.
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