Stale Gas

• Many times lawn mower problems are the result of stale gas. Any fuel, whether in your car or in your mower, will begin to degrade over time. Since lawn mowers are not used frequently outside the summer season, this stale gas problem is quite common. If the fuel in your mower has been there longer than 30 days, stale gas could very well be to blame for your engine starting and performance problems. That is why it is so important for owners to drain the mower's tank before putting it away for the season.
  
  If your mower is not starting, drain all the fuel out of the tank just as you would if you were storing the mower for the winter months. After all of the fuel has been drained, fill up the tank with fresh fuel and try to start the mower. If stale gas was to blame, the mower should roar to life.
  
  

Clogged Air Filter

• Clogged and dirty air filters are another common source of problems for lawn mower owners. If the air filter has become clogged, the engine will not be able to get the air it needs and that could make starting the mower difficult. If you are having trouble getting your mower to start, or if the mower is running poorly, a dirty air filter could be to blame. It should only take a couple of minutes to pull the air filter out and check its condition. If the air filter is in pristine condition, you know the problem lies elsewhere. But if the air filter looks dirty, changing it would be a good first troubleshooting step. To find the air filter, just refer to the owner's manual that came with your mower.
  
  

Fouled or Worn Out Spark Plugs

• Dirty or worn out spark plugs are another common source of problems with lawn mower engines. If your lawn mower is running poorly or refusing to start, it is important to pull one of the spark plugs out and examine its condition. If the spark plugs are fouled or worn, replacing them should provide better performance and faster starts.
  
  As a general rule, lawn mower spark plugs should be replaced at least once every 200 hours of operation, so it is important to keep track of how often the mower is used and replace the spark plugs as needed. Following proper maintenance procedures in this way can help keep your lawn mower running smoothly for years to come.