returning from a 2,050 mile trip (almost made it home) the engine stopped while doing 70 mph. I heard a click (like a strong switch click) and no power. on the side of the raod I used the starter and the engine spun freely, no unusual metal noises just a free spin. I manually (by hand) used the kick starter and it spun easily, no compression. no metal clinging either. any clues what may have happened and the internal changes it went through....the outside of the engine shows no signs of fracture, crack or stress.