Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
No Honda since the late 60's needs leaded fuel, if you have a sticking valve without you have the start of a mechanical problem mate
It's quite unusual to break rings on a 4 stroke engine if everything is normal, possibly more influenced by the assembly last time it was built.Also a possibiltiy if it had been stored for a long time for the bore/rings to rust and cause damage when someone tried to start it.