Comet oil system
Leaking rocker feed bolts #188 (see detail H) - Feb 2012 -
As my old friend Roy has mentioned checking that the rocker oil feed banjos have not been dished through over-tightening, may I also point out that the head size of the standard 1/4"BSF screw (#188), used at location H,  is small enough to worsen the problem. It really does not span the top of the banjo sufficiently, concentrating the force in the middle. An improvement can be made (without a lathe, Bev!), by using the 1/4"BSF screws used on some Amal carburettor petrol feed banjos, which have the head size of a 5/16" screw on a 1/4" shank. The load is thus spread over a greater area. I know the washer helps, but it is only soft copper and bends very easily.

the hybrid 1/4BSF screw with a 5/16 head is used on the Amal Monobloc carb, all sizes as far as I can tell, and is Banjo Retaining Bolt, part number 376/091. 
For those in UK, or those happy to deal with UK, try the following Amal dealers:
The bolt is also available in SS from ) part number DMD1S134
I have been using the SS ones for years with great success. Regards Dick