You said,"If it cranks",Do you mean that you hit the pedal and it just clicks and the engine does not spin?If so,I'd say the starter-solenoid is on its' way out,or you have a wiring problem.There are a couple of grounds that go from the engine to battery,and also from engine to electrical-box on the left-side.My wifes' G16 had a intermittent start problem,and the ground from the electric-panel to the harness was bad.I ran a new ground,problem solved.Look in the Gas Yamaha stickies for a diagram and follow the wires.Hope this helps.