Won't start,charged oil,cleaned spark plug and air filter.has gas.

If your tiller has sat for any length of time it may have stale gas and the spark plug may need replacing (not just cleaning). Always make sure all wiring and or connections are clean. You can check for spark by removing spark plug, insert it back into spark plug wiring, using a WOOD clothes pin to hold the wire, hold spark end of spark plug (holding the clothes pin only) on metal casing on machine, pull starter cord and check for spark. If you don't use a non conductive instrument such as the clothes pin you will get a nasty shock. If you have no spark it is time to change the plug. Always put your safety first! Hope this helps! Have a great day! If this doesn't work perhaps you will need more information.