This mower has been great for 4 years. A month ago it suddenly refused to turn over, let alone start. The engine cranks then appears to come to a sudden stop. I bought a new battery, charged it up for 3 days, still the same. The local dealer said it sounds like the starter motor so I bought a reconditioned one but that didn't fix it. I then checked the valve clearances and they were 4 thou which I have been told by the dealer is correct. I repleaced the switch on the clutch/brake pedal, no change. I tightened up all the wiring connections but it still will not turn over. With the plug removed it will turn over but appears a bit slow, its even slower than it originally was with the plug in. The battery has been back to the supplier and has been checked and they said it was ok. what am I not checking?