I have a Mountfield Mercury 16. Model 420 SP. Year 1997. I have dismantled the rotor for cleaning and maintenance, but not sure how many key pieces are required. There is a slot for a straight bar type, and on the opposite side of the drive shaft there is a space for two crescent shaped segments. I only have one of the latter type. Is this sufficient and what is the design requirement ?

Douglas Jones, April 2011

Thanks for your assistance.

Doug., April 2011

Simply re-fit they key that came off it when you stripped it. The engine is designed to fit a multitude of applications- hence the different keyways. You don't have any missing- it only has the one.

pleasant, April 2011