Model 7

hello the answer to this is No , if your looking of the pressure relef valve then your in the wrong ball park, its the biggest domed nuton the timeing case side at the back side of the case that is, it unscrews and a spring and flat disc spacer and plunger is insideto replace these items see RGM. Motors , Yours Anna J

The grub screw, in this area, gives access to the oil return tunnel that joins the sump with the oil pump. It should be totally clear with no extra gizmos to stop wet-sumping. The plug is at the point where two separate straight drillings meet to give a route around the curve of the crankcase. There is a similar arrangement in the crankshaft. Check the attached photo to ensure that we are talking about the same item. This is an Atlas crankcases but all of the Norton cases have a similar set-up.

Does this need undoing and cleaning/clearing at any point?

Generally it does not need to be touched on a model 7. I clean my oil ways by squirting some WD40 or equivalent through both ends. You can also try threading a length of soft wire through each end of the oilway tunnel and then adding some more squirts of solvent. Do not try and push any cloth or tissue through for obvious reasons. On the bigger engines some people chose to take out this grub screw to open up the oilways to 5/16" as this help to clear oil from the sump more quickly. It is not worth doing on the 500cc and 600cc engines.