NEW for 2017 is the Hot Rod Sled Shop Inc. 900 ACE clutch kit for 120" to 137" models. You've been asking and we have finally delivered. The kit was designed exclusively with Ski-doo 749 ramps and if your sled didn't come stock with them , they can be purchased separately on our website in the clutch tuning components section. (check ski-doo.com microfiche under "pulleys" to look up what your sled came with stock) Our 900 Ace kit starts pulling harder than stock after 30mph and is much more on/off throttle responsive with great backshift. It also runs the motor up to 7800-7900 rpm with 95-98mph GPS top speeds on hardpack trail while retaining great fuel economy which is why you bought the Ace in the first place. This kit truly makes the 900 Ace fun to ride- much more snappy and quicker at trail speeds. The kit includes primary spring, secondary spring, and helix. This kit is calibrated for up to 3500 feet elevation.