This Weslake type was used for junior racing in some European countries.
Specifications:
Bore and Stroke : 85.67 x 85.83
Inlet Valve:
1.77"??(4 valver = 1.1/4")
Exhaust Valve: 1.54"? (4 valver = 1.1/8")
Carburettor: 36 mm
Compression: 13 : 1
This 2 valver was also used for ice racing as the 4 valve engines were banned for iceracing.
This 1977 machine depicted in the photo is amongst the collection of Roy Young and the photos* were kindly supplied by Ben Ludolphy.
The machine is from 1977.