The Villiers S12 looks wrong for this mower all the original Royal Blade mowers had a AMAL carb.

Last week I put my Jap powered machines into storage so I can't check the spark plugs now ,
I think the Champion L10 was the right plug.
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Attachments
AMAL.jpg (61.74 KB, 60 downloads)
AMAL a.jpg (65.18 KB, 57 downloads)
AMAL b.jpg (70.88 KB, 59 downloads)