I would pull the carb/backplate off the engine and look at the back of the crankshaft. If the back of the crank is a full circle and you cannot see the main bearing, it is an L. If the sides of the crank web are open and you can see the bearing, it is an FZ. The L crankshaft has a fully circular web with a groove machined into it. A steel ring, much like a piston ring, fits in this groove and seals the rear of the crank. This reduces the volume under the piston and raises the boost pressure, resulting in more power compared to the FZ.