Re: was a Huntington...
Do you have anything between those steel-clamp motor mounts and the frame?
Last season my motor mount ate right through my Micargi frame and the downtube split in two. I was torquing on the throttle away from a stop when the frame gave out, causing the motor to twist sideways and pull the mount right through the frame. The gas line seperated and spewed fuel all over. Lucky I wasn't cruising at speed when it broke.