Ok, I see now.
Yes I agree that my engine was off a key start mower.

Is this is what you have?
[Linked Image]

I managed to get a tap to fit the holes on mine, it measured 6mm across the shank with verniers.
The thread is fine thread.
I dont have the exact size and pitch of the tap as the markings are rubbed off.

[Linked Image]

If you need info on how to tap, I can post something up, from a text book I have.
cheers


Happy is he who penetrates the mystery of things.