OK, I give up.
Dave, how did you get this picture???
"The flange broke off the back of the sprocket that goes on the crankshaft and holds the primary gear.
https://imgur.com/SXPtib"
Very interesting indeed. So do we have a situation where the cam drive sprocket failed in a way that the flange broke off but the sprocket portion remained engaged....or.....did the entire sprocket fail? Does Blake have a bunch of bent valves?
If the cam drive sprocket is the root cause (which seems plausible), how did the balancer drive gear pin end up falling out?
I think it may have been a failure that was a long time in the making. For instance, the flange fails on the cam drive sprocket, which relaxes the pinch on the balancer drive sprocket, which allows the balancer drive sprocket to start moving, which starts working on the pin, and the pin eventually gets worked loose from the constant pounding back & forth. That round pin falling out plays a major role here.
How in the world did you get that picture of the fractured cam drive sprocket?????