I'm getting pretty close on my clutching setup on my '07 600, just need a little better backshift. So my question is which force on the secondary spring has the greatest impact on backshift, initial or final?
That would depend on what % of shift you are at. The initial angle will increase backshift and RPM at slow speeds, and the final rate will have more effect at high speeds.
My guess is you would benefit from increasing the initial angle since you probably don't have a back-shift issue when you are over 45 mph.
In the powder my track speed never gets to 45 mph. Normally around 33-34. I used a blk/wht on mine and used a 58-38 .36 helix and it seems to work good at 9k elevation on up.
I notice a lot of people like the Black/White (160/260), and the Black/Purple (160/240). I've seen a few people state that it works much better in the snow than the Red/Black (140/240)
I have EPI's 160-240 that I itching to try out. I figured I don't get much over 45 unless I'm in lower altitude so losing a few RPM on the top will be ok.