While going thru my old books I came across a booklet entitled "FIFTY YEARS OF MOTORCYCLES, No. 2".
It was published by Phoebus Publishing Company/BPC Publishing Ltd, London in 1958.
Looking thru it I saw a drawing that I feel will be of interest to you Royal Enfield owners.
On page 10 and 11 is shown a 1932-33 Bullet 500 with its then popular sloped single cylinder engine broken away so the internals can be seen.
The large oil reserve is at the front of the engine and one of its 4 valves show clearly.
At the top of the cylinder is what appears to be a lever for decompression.
On the front fork about even with the bottom of the headlight is a tension adjustment for the spring in the damper.
Enjoy.