[b]Chris:

Pinhole? Strongly doubt it. Could be damage from someone using too long a screw, or possibly a crack for one reason or another.

If it's not too bad, and not on the sealing face for the cam housing, JB Weld might do fine. Can you post a picture showing the damage? Might have a better idea.

I've only seen cracks in Saito cases along a mounting lug, all have been caused by landings that were not done well. In other words, nose in at speed. Always got the crank shaft too.

Bill.