I have a question on how to remedy an oil leak on my 636 Kawi.

On the bottom of the motor, there are two large bolts, 12mm I believe with copper washers. One of whom is leaking oil and it appears the threads have begin to get stripped in the motor - probably due to vibration.

Will a helicoil fix this? Will something else? Or is the block now junk?

Yes you can helicoil it. I wouldn't run it until it's fixed. Those two bolts are for the crank. It was probably over tightened when assembled. I had a similar problem, coil hold up just fine.