How to Add Horsepower to a John Deere 4240

Your John Deere's 4240 diesel engine relies on a spark plug for ignition and an air filter to control air intake into the engine and ensure proper performance during operation. You can swap in a new spark plug and air filter parts in order to optimize the output of horsepower on your John Deere tractor. Previous experience with operating and replacing the spark plug and air filter is not required.

Replacement spark plug
Phillips screwdriver
High-flow air filter

Instructions

- 1
  Locate the spark plug on the left side of the John Deere's engine. Pull out the black ignition wire that is connected to the back of the spark plug.
- 2
  Swap out your spark plugs. Consult your parts manual to determine the next largest spark plug size from the current one employed in your 4240 model. Slide this new, larger spark plug into place and reinsert the ignition wire into the rear of the plug.
- 3
  Locate the carburetor halfway up the left side of the John Deere's engine. There is an air filter on the end of the carburetor attached by several screws. Use a Phillips screwdriver to loosen and remove these screws, then pull the air filter off.
- 4
  Install a new, high-flow air filter model in the place of the old filter. Position the new air filter onto the end of the carburetor and secure it by reinserting the removed screws with your Phillips screwdriver.

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