I’ve used JB weld on almost the identical crack on a kx125 and also a cracked crank case on my RM250 where a broken piston damaged the case. Both repairs are in the 8-10 year range and no issues whatsoever since. The stuff when used properly is amazing.IMO, I would never trust JB weld, or anything other than an actual weld, to join that joint together. I wouldn't even consider it. Even if you you used a Snap-On torque wrench to tighten all the bolts. Way too many variables.
Bring it to a competent machine shop/welder, make sure they cut a v-groove in the sides of the fracture, and have it heli-arced.
But what do I know.
Welding is a good repair, but a 100% repair is replacing the damaged component.Ive heard stories of people doing repairs such as this, but the "used properly" part is where I tend to think that most people screw it up.
IMO, a weld is the strongest join.
BUT, if you can do it without and do it properly, more power to ya.
I'd just rather spend the extra bucks to be 100%.