Polaris 2001 High-Performance Snowmobile Service Manual (PN 9916690), Page 182Get this manual
CLUTCHING Effects of Driven Clutch Helix Ramp
A larger helix angle will allow the clutch to upshift at lower engine RPMLess side force will be exerted on the moveable sheave and the clutch will upshift more rapidlyDuring backshift, lesser helix angle will backshift more easily and keep engine RPM higherA larger helix angle will make it harder to downshift and will load the engine, resulting in lower RPMsIf all other variables are kept constant, helix change with lesser angle will result in slower upshift and faster backshiftEngine RPM will remain higherA helix change with greater angle will result in faster upshift and slower backshiftEngine RPM will be lowerThe drive clutch controls upshift, while the driven clutch controls backshift through the angle of the helixThe factory helix will work well for most rugged cross country races, while helix with lesser angle may work better for high speed ice cross country racesBecause backshifting is not important in drag races, most of these racers experiment with larger helix angles for the fastest possible upshiftMulti-angle helixes are sometimes used by racers who need good holeshotA multi-angle helix reduces to smaller angle as the clutch shift out and RPM is increased to match the HP curve of the engineThis is particularly true of engines with narrower powerbandsOval and snowcross racers need good holeshot and quicker backshift for good response out of the cornersHelix angles may require change depending on individual tracksDepending on performance requirements, continuous radius, compound angle, and straight angle helixes are availableOnce again, experimentation is the best method of determining what will work best for your application