i have the same problem on 1 of my bb revos...it has a picco .26 with a bb...the problem is that when u tighten it down tight the bearing is to deep in the pull start case...so it wont retract...u can check this by just snugging the bolts and check to see if it will retract...if not keep loosing...if this is the case you can get shims to move the pull start out away from the block...