The flywheel nut is not tight enough. The drive is transmitted by the taper fit - the key is for location only. Use a torque wrench and tighten it correctly. If you have no torque wrench, use a 12 inch lever (NO LONGER) and get it AS TIGHT AS YOU CAN. For most people, that's about 80 foot pounds, which isn't too far out.
phil_saunders@bigfoot.com
Phil Saunders, August 2008
