Rich or lean, it has no effect on cranking speed and he is correct. First step would be test the battery. If the battery passes the test and is large enough for this engine, do a voltage drop test on each leg of the circuit. If there is excess resistance somewhere, a voltage drop test will find it. If there is no excess voltage drop, he needs a starter.
(This assumes that the engine is not kicking back on the starter, only slow cranking speed.)
This message has been edited by Noble1Tech on Aug 10, 2012 4:20 PM