The best/cleanest solution is to get a pair of matching cases. Its a lot of work, but not really.
Or you can have it all welded and tap a smaller threaded drain valve there, or you can have it welded over completely and sealed. Youll have to use the sump screen to drain and that would be a mess every time.
Or you can be an idiot and jam silicone and JB weld in there and risk it... Yes Ive seen some things on some of these bike forums.
Welding the case will most likely require it to be removed. You dont want contamination on the welds. Probably the only way youll get a welders hands on it too.
what would I do?
- Have it all welded over and drill/tap a drain valve there, easy.