Small Engines (Lawn Mowers, etc.): B&S Balancer Issue, head gasket failure, hairline crack

Question
I have a B&S 18 hp rider engine Model 31H777 0202 E1 I have been repairing. The engine threw the conn rod. (I believe this resulted from oil level being low due to internal head gasket failure burning up oil supply) I have since had the crankshaft professionally refinished, installed new conn rod, camshaft, governor and balance weight to repair the damage. (part of the balancer where it rides on the sump rib had been broken off) When I started motor up, seemed ok at first, then started metallic clanking. I removed the sump to find that the rib in the sump (cast aluminum part of the sump that the balancer rides on) was sheared off neatly at the transition (radius) from the machined surface to the cast surface. the balancer was fine...no damage. Do you have any thoughts on why this happened? Seems like I've seen some threads on balancers being "loose" but don't see how they can get loose. Also is there supposed to be a spring inside the governor assembly? Thanks for any info you can provide.

Answer
Hi Ron
 I've been doing some research on your question. The only possible answers I can give you are these: The rib on the sump plate could have been damaged when the rod broke. Even a hairline crack in the aluminum can weaken it and under stress can break off. Another reason could also be that you may have torqued the bolts too tight. As far as the governor, the springs will be external. Hope this helps.