Dating stationary engines
It has a bore of 51.5mm and a stroke of 47.6mm, giving it a cubic capacity of 98cc. According to the Small Engines Forum:" the best thing to do is the thing that kev said to do, all you have to do is where your exhaust is there willl be a thin metal plate running around the back of the the engine and if you take off the exhaust this thing will come off then get a wire brush or something like that and take the dirt away from the inside and in a little circle it will say A. H and then the date of your engine." I have not checked this on mine yet.The 2S replaced the similar 2A some time after 1947 - offhand I can't find the exact date. I need some different parts before i can start it . maybe a new piston, gaskets and maybe some carburetor parts since the petrol seems to owerflow right trough. Anders Norway Bit of History: JAP goes back to the 1920s and 1930's, they made big motorcycle V-twins and small two stroke engines. Prestwich, not Prestwick) Peter Peter, Thanks for pointing out the incorrect spelling of the name. Another good book to get hold of is "The JAP Engine" by A. Fenner, published by Arthur Pearson Ltd in the 1950's.
Prestwich Industries Ltd., Northumberland Park, Tottenam, London N17, England. Peter At the air case in front of the engine its a logo stamped in with the numbers 1945 ..maybe the date.
seriel number are C/1/72405/S at the bottom: BA68955 over the bottom underneath of the bracket for ignition: HB2 the top of the block:14831F.