The stock Honda TRX 400EX ATV typically produces about 28 horsepower at the crank, with roughly 20–25 hp available at the wheels depending on drivetrain losses and tire setup.
Known for its reliability and approachable power, the TRX 400EX is a 397cc four-stroke single that was popular for trail riding and beginner-friendly performance. The exact horsepower varies by year, emissions tuning, and whether the engine has been modified or serviced to factory specifications. This article breaks down those numbers and what you need to know about real-world performance.
Crank horsepower vs wheel horsepower
What the numbers mean
Crank horsepower is the engine’s raw output measured at the crankshaft. Wheel horsepower reflects what actually reaches the ground and is typically lower due to losses in the transmission, clutch, and tires. For the TRX 400EX, crank figures are usually cited around the high-20s in horsepower, with wheel horsepower in the low-to-mid 20s under typical riding conditions.
Typical stock figures and what to expect
In stock form, most sources approximate the TRX 400EX at roughly 28 HP at the crank, with a wheel output around 20–25 HP depending on year, altitude, and exhaust or intake setup. These numbers reflect factory configuration and may vary slightly by market or emission controls.
Modifications and real-world performance
Bolt-on upgrades such as exhaust systems, air filters, and carburetor tuning can yield modest power gains, typically in the 1–5 HP range for simple bolt-ons. More extensive engine work or aftermarket cams can push output higher, but such modifications require careful tuning and reliability considerations. Always consult a qualified technician when pursuing significant performance gains.
Summary
The Honda TRX 400EX delivers roughly 28 horsepower at the crank in stock form, translating to about 20–25 horsepower at the wheels depending on conditions. Real-world numbers vary with year, market, maintenance, and any modifications. For riders seeking the best balance of reliability and performance, the TRX 400EX offers approachable power and proven durability.