With the Ninja 500 and Ninja 400 being very similarly priced there’s a question to be made which one would be the better one to get? The Ninja 500 is really a 451 cubic centimeter sized engine with the Ninja 400 being a 399 cubic centimeter sized engine. Both the Ninja 500 and 400 output roughly the same horse power outputting 44.3 horsepower with the Ninja 500 having a slight edge with torque outputting 31.4 foot pounds apposed to 27.2 but with the extra torque also comes a little extra weight as well roughly an additional 10-15 pounds.
Both motorcycles are also equipped with similar suspension and brakes with the Ninja 500 going away from the pedal style brakes which has been shown to be more effective for braking. The Ninja 500 also comes with a more advanced dash but besides that both bikes are incredibly similar with the only changes made are the style, engine size, weight, and dash.
I would recommend getting the Ninja 500 solely based off the additional torque but either way there are so incredibly similar that there wouldn’t be a too noticeable difference between the two but considering they are priced evenly why not opt for the larger engine.
| Specification | Kawasaki Ninja 500 | Kawasaki Ninja 400 |
| Chassis | Steel trellis | Steel trellis |
| Front suspension | 41 mm telescopic forks | 41 mm telescopic forks |
| Rear suspension | Monoshock | Monoshock |
| Wheel size | 17/17-inches | 17/17-inches |
| Front brake | 310 mm disc | 310 mm disc |
| Rear brake | 220 mm disc | 220 mm disc |
| Wheelbase | 54.1 inches | 53.9 inches |
| Ground clearance | 5.7 inches | 5.5 inches |
| Seat height | 30.9 inches | 30.9 inches |
| Specification | Kawasaki Ninja 500 | Kawasaki Ninja 400 |
| Engine | 451cc, parallel-twin, liquid-cooled | 399cc, parallel-twin, liquid-cooled |
| Bore x Stroke | 70×58.6 mm | 70×51.8 mm |
| Power | 44.3 horsepower at 9,000 RPM | 44.3 horsepower at 10,000 RPM |
| Torque | 31.4 pound-feet at 6,000 RPM | 27.2 pound-feet at 8,000 RPM |
| Transmission | Six-speed | Six-speed |
| Compression ratio | 11.3:1 | 11.5:1 |
| Final gear ratio | 43/14 | 41/14 |
| Claimed efficiency | 61 miles per gallon (3.8/100km) | 60 miles per gallon (3.9/100km) |
https://www.topspeed.com/2024-kawasaki-ninja-500-vs-ninja-400-key-differences/