That is damage and should not be there. I have had it suggested that if a suitable piston from a diesel engine can be found it is possible to machine the crown to the required profile, as the diesel piston will have a much thicker crown. If you need a better copy of the drawing let me know.
Photo files need reducing in size, they need to be no more than 3072KB. For microsoft users there is a guide in help and information section of forum.
The attached is a photograph of drawing for piston, the original is at MERL, Reading UK.
Villiers Mk12/2 will probably need points cleaning to get a spark. Magneto can suffer from failed coil or condensor. Carb will also need a good clean out.
Welcome to the club, the attached document describes how to reduce photo file size.
Club member Jim Beacon is the Auto-Culto expert and I am sure he will be able to offer help, advice and information.
561602 despatched on 10-5056 and delivered on 29-5-56 to J Olivar & Sons, Waverley Huts (Hurs, Nurs? hand writing is not clear), Darwich, Melrose. Sourced from T Couchram.
What is the other forum?