Originally Posted by Kewadin
The deck has: MZAM-6030934 HXA .....&...HR215 KM. This mower was bought years ago, can you tell what year it is? Can you suggest what to look at and what you think I should replace while I have it open,(if I get it open)?
That serial number is old, and not in the online database I have. I'd guess it was made in the early 90s, maybe late 80s or so, but that's just a guess.
Anyway, the Roto-Stop was made in two different designs on that model. I've included images from the shop manual and parts catalog to show you. If you have type "A", then you'll need a strap wrench to hold the flywheel when loosening the 10x25 mm bolt. It's a normal left-hand thread. Torque to 36-43 lb.-ft. when reinstalling.
A compression and leak-down test would help you zero in on what might need replacement in the engine. Specific measurements of some internal parts might be needed to to see if they are past their service limit.
I'd strongly suggest you get a full paper shop manual; it will be priceless in helping you with overhauling the engine. Honda sells them on eBay with free shipping and free updates for three years; here's a link:
Honda Power Equipment Shop Manuals on eBay
Caveat: I work for Honda, but the preceding is my opinion alone.