Hi William,
There isn't much to add to John's comments but some caution.
The gasket behind the pump must be replaced. It might leak air. If you suspect this is happening, you can use two gaskets.
Wash the pump out carefully in a solvent. Tap the ball bearings into their seats (with a small hammer!)
The original W/NG had ball and spring arrangements to regulate oil pressure (photo is of a '37 NG). This could well be the problem. If you have this setup, undo the bottom nut, not the screw above it. This need to be checked, cleaned and refitted. Again, tap the ball bearing, fairly firmly, (same small hammer). If this isn't working, or the pipe to the rockers is blocked, oil will just go back into the engine.
Put some fine wire through the oil pipe to make sure it is clear.
Sometimes new oil with detergent - like 20/50 ie GTX or similar, will loosen very old oil deposits, especially if the motor hasn't been running for a long time. These can swim around in your oil system, and might cause a problem with the ball valves. If this is the case, it would be a good idea to wash out the oil tank very carefully.
Also put in cheap oil and change it often.
If there is feed to the bottom end, maybe you could squirt some oil into the rockers with an oil can before starting the bike.
This info is in the W/NG and earlier manuals on the club website. http://www.arielownersmcc.co.uk/members ... ide6_7.jpg
http://www.arielownersmcc.co.uk/members ... manual.htm
Brenton