From the angle of the pic, it doesn't look too bad. Maybe run a thin smear of a fuel resistant RTV (Yamabond or Hondabond) around the edge of the seal? I'm just not a fan of JB weld inside of a engine, others have a different view...
Does this use a metal edged seal? I gotta wonder how the chips got there.
It might suck air around the edge there, depending on the type of seal and how well it fits. If you're paranoid, you could use oil seal retaining compound (similar to loctite) to "glue" it shut there. If you have a crankcase tester, you can find out for sure after the cases and top end are reassembled by setting the engine on its side, flywheel side down, and with the clutch still off, fill the main bearing with gear oil. If under < 5psi or so you don't see any bubbles coming through the bearing, you're fine.
Fraserd, I did not mean you personally. However, if I offended you, I apologize. I am kind of wound up right now as I am working on scooters and motorcycles on the side to make ends meet. After working many nights and weekends, I have seen more crazy stuff done to these engines and sometimes it's hard to make them right again. It is even harder to tell the owners that it will cost more to get it right. But that's my problem, not yours and I should not have dumped on you.
Honestly, it does not look that bad and the advice of using yamabond or an equivalent sounds spot on. You would just have to use some heat if you need to take it apart again. But you should do that anyway to remove the bearings - easier on the case halves. Good luck with it.
No problem mate no offense was taken. All is cool. Just a shit thing to happen when you are doing the right thing. I should of preserved with getting it straight out. Going to try 3 bond high temp
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