You are a little rough for break-in!
That wasn't even wide open lol. That was maybe going from quarter to half throttle
I think you either had a chain out of proper alignment or defective in some way or another...I had a 415 fall apart on me some years ago that I knew was in perfect alignment and I wasn't even goosing it...lol...lol...I was in a 15 MPH school zone at the time...lol...lol.
Alignment was perfect and everything. It looks to me like the pin hole elongated trom the torque enough that the pin slid out because it slides right back together but is way too loose to press back together
You could try peening the pin back down again to lock it back in place...That is if you really trust that chain again...NOT...lol...lol.
Nah, I've got more chain. Lots more.
That's what it looked like on my bike, so I stacked some washers behind the aluminum block for the rear mount. Held it out further and works good.
