Dr Graham Smith writes: "Can anyone identify this 2 stroke engine? It has a Bing carburettor and ML magneto. It is about 150cc and has a decompression valve on the cylinder head. There is a small circular brass plate on the casting which contains the magneto drive chain which reads, "J A Prestwich" which suggests that it is a JAP, but this may have been added later. Please ignore the bike in which it is fixed as this is one that was made up last year to look like an Indian racer. We would like to find out the age, is it a genuine JAP, and what it was used for. Any information would be much appreciated."