Nice find. Here's some plug reading info from the master.
http://www.strappe.com/plugs.html
Holed pistons aren't uncommon on those engines, then the molten piston crown wipes out the crank bearings.
Probably a good idea to put new crank seals, bearings and top-end in it before it seizes at the most inopportune time.
Learn to ride with two fingers on the clutch to catch it if/when it sticks...