The EVAD 4 has a triangulated space frame with an alloy undertray, and centre section. The nose and tail sections being quickly detachable glass fibre panels. Removable padding in the upholstery of the reclining seat, and fully adjustable controls, enable a suitable driving position to be obtained.

The rear engine is mounted in dural engine plates which are rigidly fixed in the chassis for added rigidity. Drive is by chain to a quick change rear axle sprocket, and then by rubber doughnuts to the wheels. Chain adjustment is obtained by rocking the centre drive unit. Suspension follows modern practice, and is fully adjustable, pivot points being rubber or nylon bushes and rose joints.

Springing is by Armstrong coil spring damper units. An 11" hide-covered steering wheel controls the steering through a rack and pinion steering box. The braking system is made up of 7" alloy drum brakes, operated by twin balanced master cylinders. Fuel is contained in a tank behind the seat, and is pumped by either mechanical or pulse pump to the carburetlors.