I have a older 42 inch cut riding mower/Craftsman. Everytime I go to put the blade down it putts out on me.

 

Sounds like you probably have a bad seat switch.

 

Or maybe the connector has just come loose. It's made so you cannot disable the safety feature by simply disconnecting the switch.

 

Generally I have found that if it's the seat switch causing this problem, then it will also surface whenever the clutch is released.

Does it also die when you release the clutch pedal? If so then the seat switch or plug switch is the most likely culprit.

It could be related to your fuel (old or contaminated with water) or your carburetor may not be delivering enough fuel to the engine when the load from the blades are applied.