More and more interesting. RY is the prefix for the standard MK 14A water cooled engine with Villiers Autolube system. RYP identifies the petroil version without the Autolube. I have a feeling the RYR engines are really RYP engines but either poorly stamped or poorly written on the record cards. Hopefully I can eventually sort this out as I know someone with one of the original Villiers factory despatch books. Getting to actually look at it has been a bit of a song and dance. Nothing intentional, just life and family getting underfoot.
I saw someone has made a nice new solid boss engine sprocket on b'knighted shot of a 'W'. Very nice but why bother. Villiers listed two screwed bosses for either a 2 1/2" or 3" chain centre line and a range of 14-24 tooth engine sprockets to suit. Villiers made bicycle parts, sprockets, coaster hubs, pedals, etc, by the gazillion so just used their bicycle machinery to cut a standard L/H bicycle rear sprocket thread on the boss and made engine sprockets as they made rear bicycle sprockets.
One last question. How many speeds in the model 'W' gear box? Is it a three or four speed box? Four speeds allow one to keep up a far better cross country pace. Little pace is lost from a drop to third. Not so on the wide ratio three speed boxes of the day.