[Thumper]

Here is a completely different idea.

A replacement engine costs under $500. You may even choose to upgrade to a 249cc engine, which might cost a bit more. But the amount of work involved and chances of failure really beg the question, "Is it worth the effort?"

The only way to fix this problem with certainly is to break the crankcase in half and replace the broken side. But once you've done that, you may need to replace the seals on the ends of the shafts in addition to the gaskets. What would the parts total be? Can you find them?

And it is a whole lot of labor. Do you have bench space in a shop to do this work? Once it is all back together, it is a used Chinese engine that has been broken down and rebuilt. Sure, it can be done, but swapping in a fresh engine is much less work.

Just a thought. The quick fix (JB Weld or welding) could work. Just thinking that if it fails, what next?