There are a few basic things you can troubleshoot if your Cub Cadet doesn't start, run or mow properly. This usually means one of two things: no spark from the plugs, or no fuel to the engine. With some methodical work, you may be able to determine exactly what the problem is with your mower and fix it, or at worst you will rule out the simple possibilities and be certain that calling in a repairman will be worth your while.
Check the spark plug. Open the hood of your Cub Cadet and find the spark plug wire. The spark plug wire will generally look like a big black wire that can be found on the side of the engine. Pull the spark plug wire off the spark plug. Take your spark plug wrench, which will have an opening that neatly fits over the spark plug top, push it onto the plug itself and remove the spark plug by turning it in a counter-clockwise motion.
Squirt some starting fluid into the spark plug hole. A one second squirt should be plenty. Put the spark plug back in using your wrench, turning it in a clockwise motion. Attach the spark plug wire by pushing the end of the wire directly onto the spark plug.
Start the mower. If the engine runs for only two or three seconds and then shuts off, you have a fuel flow problem. If the engine now runs fine, then you had a spark plug issue that is now resolved.
Remove the fuel filter. The most common fuel flow problem causes are plugged gas line filters. Fuel line filters are located in a line form the gas tank to the carburetor. The carburetor is located directly under the air filter box, which is big and black. This is located next to the engine which is located under the hood of the Cub Cadet. The fuel filter looks like a miniature plastic see-through barrel which is approximately 3 inches long and is attached to a black hose on both the front and rear side. The front side is the side that is closer to the carburetor, and the rear is the side on the other end of the front. There will be a couple of hose clamps holding on the fuel filter, and you will need your flat-bladed screwdriver to remove these clamps. Find the slot on the clamp that holds the fuel filter on. This will be where you put your flat-bladed screwdriver into; place it into the slot on the front clamp and turn counter-clockwise to remove. Repeat this procedure on the opposite side.
Replace the fuel filter. Go to your nearest lawn and garden store, give an employee the serial number of your Cub Cadet, and he will give you the correct fuel filter to replace it. Put the new fuel filter in the place of the old one and clamp it into place.
Restart the motor. If it starts, then the clogged fuel line was the problem. If it does not, then you may need to replace the spark plug. You will remove the old spark plug as you did when you squirted in the starting fluid, but then replace it with a new one. The best way to get a new spark plug is to remove the old one and take it to the store with you, then buy a matching plug.
Replace a spark plug if necessary. The most common cause of electrical problems is a bad spark plug. Again, with the serial number of your Cub Cadet, go to your nearest lawn and garden shop, and get the correct spark plug. Install it by removing the old spark plug just as you did earlier, then replace it with a new one instead of just putting the old one back into place.
Resolve any cutting problems. If your mower does not cut, check the belts underneath. They should be free moving and able to turn by hand force if necessary. If they are not free moving, test each blade individually. Making sure the key is out of the ignition, reach beneath the lawn mower and firmly grasp each blade. Attempt to spin them one by one. If one of the blades does not spin, the bearing on the spool is bad and will need to be replaced. That cannot be done at home and will need to be taken in to a lawn and garden shop.