Readying JLT-823 for the Scots Games, I screwed the Pilgrim down a bit for a slow day of parade work, added a bit more petroil, and fired her up. She started readily, ran not too smokily, and then on throttle overrun, a loud bang! Fearing the worst, I inspected the left side crankcase door to find the strap snapped off at both ends and the door blown out. No damage apparent to the big end, no signs of contact with the inside of the door, so it seems like a combustion event. Might have had a bit too much spark advance. Anyone ever had this happen?