The all-new Roller Tower P-Drive primary clutch used on all the G-4 850’s from Ski-Doo has received another ingenious tweak designed to improve clutch alignment, reduce belt heat and soften vibration.
Listen up, because this is weird science. The fixed (back) sheave on the new P-Drive for MY 18 is actually cast so it wobbles. There’s .024 run-out on the sheave when installed on the crank.
To make this vibration absorbing effect work, the clutch and crank stub have to be timed together so the “wobble” occurs at a precise vibration cancelling moment during the engine’s 180 degree firing order.
The crank stub and the taper on the sheave are “D” shaped to ensure the clutch goes on correctly. The slight wobble also improves belt tensioning while compensating for vibration induced belt misalignment.
Yeah, we said it was weird science. Once again Ski-Doo is tweaking our sensibilities with ground breaking innovation.
Who would have dreamed a wobbling clutch could be a good thing?
Read about this technology here: