When evaluating a 400cc go kart, focus on the engine type (typically 4-stroke, water-cooled) for consistent performance and longevity. Ensure the frame is constructed from high-tensile chromoly steel with robotic welding for structural integrity. Key performance metrics include a top speed of 60-80 km/h, a hydraulic disc brake system for reliable stopping power, and adjustable shock absorbers to handle varied terrains. For B2B buyers, verifying the transmission type (CVT or Manual) is essential to match the end-user's skill level.