xr3i sump, ( i think im right in saying this)doesnt have the little hole in the plate in the sump for the oil to drain right to the bottom.

The noise, when i rev it to say 2k to 2.5 and let off there is sometimes a tapping / knocking. unfortunately i cant tell. Can you use some kind of a stethascope to hear it?? or is there something in perticular, as I dont want to take off the arp's incase there isnt a problem with them.