How would you fix this?

[Zippymbr]

I opened up an old case I bought off a member here to replace the bearings and crank and saw some deep pitting.

 

[chris zautner]

Looks like white death. Is the surface where the two cases meet together pitted?

 

[Zippymbr]

The mating surfaces are straight and true. Just inside its all chewed up. Looks like the piston ingested something and the crankcase got beat to hell inside as the foreign object bounced around inside. I can use a Dremel and smooth it out and paint or I can fill it in with met Tig welder.

 

[chris zautner]

Ok just clean everything up with the dremel don't worry about tig welding it.