1. The safety switch is engaged. Most riding mowers have a safety switch that prevents the engine from running if the deck is raised. This is to prevent the mower from accidentally cutting off fingers or toes if someone reaches under the deck. Make sure that the safety switch is disengaged before you lower the deck.
2. The PTO switch is not turned on. The PTO (power take-off) switch is the switch that engages the mower's blades. Make sure that the PTO switch is turned on before you lower the deck.
3. The engine is not getting enough fuel. If the engine is not getting enough fuel, it will stall when you put a load on it, such as when you lower the deck. Check the fuel level and make sure that the fuel filter is clean.
4. The spark plug is not firing. If the spark plug is not firing, the engine will not start. Check the spark plug and make sure that it is clean and properly gapped.
5. The drive belt is broken or slipping. The drive belt is the belt that transfers power from the engine to the mower's wheels. If the drive belt is broken or slipping, the mower will not be able to move and the engine will cut off. Check the drive belt and make sure that it is in good condition.
If you have checked all of these things and the mower is still cutting off, you should take it to a qualified repair technician.
