From Bikeman website:
"Want more top speed and acceleration out of your Diamond Drive sled? This is the ticket for an easy 5-8 mph on most sleds. By converting your secondary clutch to using the old style torsional spring, it allows the clutches to shift out faster and go into overdrive. This kit also has adjustable spring conditions for tuning. For 2007 models you will need to get a 2005-06 style helix as well."
All you need for tools to make adjusments are a 5/32" allen wrench and a ACT drive spring tool from Black Diamond. The cover has a three hole pattern in it that accepts the drive spring tool to twist it into place and fasten with three allen bolts. They retail for $14.95.