The only 250cc Sunbeam of 1936 was the Model 16. This was new to 36, and had a high camshaft and hairpin valve springs. It had a Burman gearbox, but proved to be a poor design and was not at all successful. The sports variant had an upswept sports exhaust system.
Sunbeam were amalgamated into AMC in 1937, so this was one of the last bikes they made prior to that.
Nigel.