Mower dies when engage blades

Kathy Kindred First make sure that your belt is routed properly and that your blades can spin freely. Sometimes the spindles for the mower, rust and require an incredible amount of torque to turn, which could cause your engine to bog down. You check that with the engine OFF (of course, but just to make sure ;-) Next, you want to check if your fuel mixture is wrong and your engine be running too rich or too lean. Check your air filter and the mixture screws if your carb has one. Depending on model, adjusting the fuel mixture may or may not be possible. Also, check your plugs for a proper gap. It might help if we can get the engine number from/model number from you, so we can research certain areas specifically the carb.