If it's going to bother you, what I would do is disassemble it, get the angle grinder out. You can get a nice diamond tipped cutting wheel. I would do that and cut "all that" off as close to the outside edge of that counterweight as I could, then see "what's left". Problem is, that hole has been completely filled in "with something" and you don't know if it's all weld "or what". When you get the weld cut off, it might all let go and come out. Then again, if whoever did it welded to fill the entire hole in, then........well......LOL
340 cranks can be had reasonably. I guess you're going to have to make a decision at some point. "I" would try to get that off if it was mine. What have you got to lose?
If you take it to the shop they are going to have to do everything except put weights on or take weight off to check the balance. In other words, you'll basically be charged for a balance job. Even if it checked out good, you're money out at that point and "I" still would be leery of "THAT". lol
You can say whatever you want about centrifugal force, BUT if that lets go while running, all theories now become a nasty reality.
