Correct airgap adjustment of adjustable ignition modules will usually ensure easy starting and running, but too little airgap (especially if the magnet is already scraping along the ignition module) can cause kicking back during the starting process.
This kick back, also known as the ‘Granny Kick’ is caused by over-advanced ignition timing because the angle of the magnetic travel through the airgap changes/advances. The Granny Kick can also happen on engines with correctly adjusted airgaps, especially on engines with very small inertia. In such cases, an increase of the airgap will delay ignition timing and reduce Granny Kicks.