Tony, if you were to remove the left cover there's a tube like part on the engine casing that the idler gear shaft fits into. There's also a corresponding part of the cover that secures the shaft's other end. The part that broke is the top half of the mounting on the engine casing but not on the cover. You can see this on the last page of the clutch chapter in the shop manual (if you have one). The end top half of the tube socket broke allowing the shaft to lift and no longer allow the idler gear to engage the starter gear.
They would have to recast the casing to improve it and they may have beefed up other fittings when they made the change. I assume it would have some sort of inner steel sleeve or something to make it stronger.
