Translation:The motor and the wheel will be necessary.
When a distinction between a "motor" and an "engine" is made in English, a motor is a device that draws its energy from an outside source (like an electric motor) and an engine converts fuel into energy within the device (like a diesel engine).
It usually doesn't matter much, though. Unless you're locked in a room full of engineers, most English speakers don't know the difference. Besides, this sentence could have have been about either an electric or gasoline-powered car!
The audio seems to have been fixed., “neces
aj” is clearly audible.
For completeness' sake,
necesoj would not be grammatically correct, as neceso isn't a synonym of “necesaĵo” but more of “neceseco”. Here's what NPIV says:
neceso 1 Absoluta bezono: senti la neceson silenti… 2 neceseco: …la neceso, krei novan literaturon…