Holy helll i was about to split apart a good running motor. I can ask the guy who welded the swingarm back into working order, Im sure there will be some metal going inside of it, if its still on,  should i just dump some motor oil in the hole to help clean it after the grinding? I dont wanna waste precious type f atf, which is hard to find locally in northeast pennsylvania.

Drain the oil the biggest thing with tig welding is getting everything as clean as possible especially with stuff that has had oil soaked castings for almost 30 years.