We'll I had a major scare and not sure if I've damaged the engine. I had the chain bind up in the clutch / drive sprocket and lock up the back tire while underway. I left about a 10 ft skid mark and was happy not to hit the dirt. I had a long walk home and was super bummed. It turns out that after shortening the peddle chain and adjusting the wheel in the frame it worked itself loose dropping out of position and creating excess slack. The chain got caught around the sprocket and scared the life out of me. I may need to add a tensioner to the other side too. I guess the chain stretched as I've heard they do. I hope the clutch is not damaged.