This is the pump with the check valve pressed in . Note which side is facing out towards the engine case.
What the feed side valve looks like before pressing . Note chamfered end .
Look closely, you will see the aluminum shavings built up on the perimeter of the hole when the valve was pressed in. The oil pump is partially disassembled to see this. Just remove the 4 bolts and separate it a bit is all that is needed.
These shavings must be removed after pressing . OR the upgrade will fail . This is my oil pump you are looking at. This information and directions were given to me by Norton Motorcycles UK .