If it has been sitting in a shop for two years I would start by draining the gas tank, then change the fuel filter, drain and clean the air filter. If that doesn't clear the problem, check the vacum advance on the distributor along with plugs , wires,and rotor. As far the timing, there is no timing chain on that engine, it is gear driven, unlikely that is the problem. If the gas was in the tank for two years sitting in a shop the carb. could need a good cleaning also. good luck finding the cause of your trouble. We are all hear willing to help you, just let us know what you find.
