The one way bearing is likely slipping or the pull start isn't engaging.  Take <span style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.296875); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">the pull start off and try to turn the engine by just grabbing the one way bearing.  That will confirm if it's locking when turned or not.</span>