The bike looked something like this when new except that it had the famous "Jampot" shocks and springs at the rear, so maybe the motor was an earlier model inserted in the sprung frame?
engine
single cylinder OHV 4-stroke
cylinder bore
piston stroke
cubic capacity
497cc
bhp at rpm
N/A (estimated 18 bhp)
lubrication
Dry sump
carburetors
One Amal Monobloc
gears
4, right-hand foot change
chassis
Tubular steel
tires
weight
max. speed
N/A (estimated 113kph)
brakes
single leading shoe drums front and rear
Note
the heavy duty fork-brace and special Primary drive cover! Classic farm
engineering!