Here's a 84cc gasoline four stroke. The Walbro is a barrel type. It will run in the high 6,000 rpm area to effectively take advantage of the prop. A 24 fluid once gas tank will be fine for a 12-15min flight. It uses a spark plug a lot like the plug in a Husqvarna 550 except that it is non resister and shorter threads. NGK CM-6 and is the same plug used in a Honda generator. The ignition is shielded and there is a resistor in the shielded spark plug cap.