Small engine advice tip # 2, When you can't get a spark by sanding the coil and magneto you will want to check your coil with an ohms meter. Next, test to make sure the negative wire is on the surface of the small engine that touches the the magneto and the positive in the spark plug boot is touching the metal. A good coil will read anywhere between 1.5 to 5 ohms. A bad coil will read a lot higher such as 7000. If your coil has spark when it is cold but not when it is hot it may have an intermittent coil. Make sure your coil is cool and has spark. Heat it up with a heat gun or hair dryer and test it again. If there's no spark, my advice to you would be to take it in to the mower shop and get a new one.