Thanks all for coming back, helicoil is the way to go but I won't know  for sure until I make with the spanners what I'll looks like an expanded diagram of the engine. The pesky little bolt (or stud) in question can be view with awe and wonder in the Clymer bible, chapter 4, page 81, revelations (figure) 46.It's the criminal or hooligan with the locating dowel on top that lives beside the cam chain tensioner bolt and washer, and as you can see there doesn't seem to be to much meat for drilling and tapping where it threads into the cylinder at the bottom of the head, but that enlightenment will have to be pondered upon until I make a forensic inspection of it,,wishing all the best to you all,, and THANKS!