There is a small electric motor that connects on the back of the engine in place of the pull-start. Its that small electric motor that starts the gas motor when you use the ez-start. You will need one of these:
http://www.amainhobbies.com/product_...harness-TRX-33
This has both pieces that you need. You will also need a 7.2 v battery for it - my old ez-start has a Tamiya connector, but I think the new ones are black and different - I'd check before buying a battery-