all of a sudden motor acted like it ran out of fuel. now it wont start. changed diaphragms in vaporizer, didn't help. checked spark at plugs, have spark. checked fuel supply at vaporizer, have fuel when line is cracked and engine is cranking. checked hose coming out of vaporizer going to carburetor to see if fuel was coming out, its not. looked in oil fill cap hole to see if rocker arms were working, they are. Ether wont even start it. Is it possible that timing belt/chain jumped, and now its way out of time??