Just four years after its inception, the 2002 Honda 400EX (a.k.a. TRX400EX or SporTrax) successfully earned a reputation for reliability and fun. After all, the quad hails from one of Honda’s longest mainstays in the sport-ATV segment. Unadulterated, powerful, and robust, this four-wheeler laid the foundation for pure-sport quads and introduced 4-strokes into the ATV landscape – with a Baja 1000 championship to boot.
The 2002 Honda 400EX is part of the SporTrax lineup, signaling the rebirth of sport riding and 4-strokes taking over four-wheelers. Boasting an XR400R-inspired engine, independent double-wishbone front suspension, and a 65-mph top speed, it continues to be the community’s favorite entry-level quad.
Honda launched the SporTrax to improve the competencies of sport quads and bring back the element of fun in exploring unbeaten paths and off-road. And no other machine could have done it better than the 2002 Honda 400EX. Read on and discover the specs, features, and pain points of this well-loved game-changer.
The 2002 Honda TRX 400EX
Despite being deemed an underdog, the 2002 Honda 400EX was in every way a pure-sport machine as efficient as any other 450-class racers you will see on present MX tracks. It is the 4th installment of the Sportrax lineup that first came into fruition in 1999. A wake-up call for the riding community, the launch of the SporTrax was like welcome rain after a decade of drought. It may not have entirely been what hard-core riders had hoped for in a sport ATV. But when it came to fun and capability, the 400EX surely delivered.
The Elusive Goal
More than being a successful trail tamer, Honda intended the 400EX to dominate motocross and GNCC arenas. This is the primary reason behind equipping the 4×4 with an XR400R-adopted power mill alongside other race-ready basics. Out of the crate, the quad had a lot of promise. It even went on to win its first-ever Baja tournament.
However, it failed to create the same impression on the much-coveted racing tracks, as the then reigning 2-strokes were still more powerful and agile in the said environment. This is not to say that the Honda 400EX was less an enjoyable vehicle than other sport quads in the market. It was easy to maneuver, had the perfect piston displacement, and was every bit a sport-racer. However, the lack of enhancements through the years led many riders to perceive it as a mere recreational machine.
2002 Honda 400EX Specs & Features
Engine
An air-cooled single-cylinder 4-stroke power mill, a Radial Four-Valve Combustion Chamber, and a 38-mm piston valve with an accelerator pump breathe life into the Honda TRX400EX. Engine displacement is 397-cm3 (24.23 in3) and pairs with a bore-stroke ratio of 85 × 70 mm (3.35 × 2.76 inches), a compression ratio of 9.1:1, oiled-urethane-foam air filtration, and dry-sump lubrication. This configuration lends to a top speed of 65 – 72 mph (105 – 116 km/h) and 28 RWHP (20.59 kW) horsepower.
Fuel & Lubrication
Engine oil recommendation is 2.2 liters (2.3 US quarts of SAE 10W-40 oil or its equivalent. This is slightly more than the oil requirement for the 2004 model. Use SJ+ Pro Honda GN4/HP4 motor oils that meet JASO T903 MA standards to ensure top results.
Tank capacity is 2.64 US gallons of unleaded gasoline. Stay clear of lower-octane gasoline to avoid pinging or spark knock. Otherwise, it is natural to encounter a bit of this issue under a heavy load.
Drivetrain
Power comes from a 5-speed constant-mesh transmission and a cable-operated wet, multi-plate clutch assembly (with a 1-N-2-3-4-5 shift sequence). A DID520V6 or RK520 SMOZ10S O-ring sealed chain (96 or 120 links + joint) handles wheelspin. A gear-driven counter-balancer reduces engine vibration and makes for smooth maneuverability of the sport quad regardless of riding conditions.
| Primary Reduction Ratio | 2.826 (23/65) |
| Final Reduction Ratio | 2.533 (15/38) |
| Transmission Gear Ratio – I | 2.917 (12/35) |
| Transmission Gear Ratio – II | 1.938 (16/31) |
| Transmission Gear Ratio – III | 1.474 (19/28) |
| Transmission Gear Ratio – IV | 1.182 (22/26) |
| Transmission Gear Ratio – V | 1.000 (26/26) |
Controls
The placement of most of the wheeler’s controls – like its clutch, start button, headlight/dimmer/engine stop switches, and parking brake levers – are found on the left handgrip and have remained untouched even for later-year models. The choke lever and gear pedal are on the same side of the engine.
The ignition switch and neutral indicator lamp are on the center console, while brake and throttle-related levers are on the opposite side, near the right handgrip.
Ignition
Like later models, an electric starter and an ICM (or Ignition Control Module) bring the 2002 Honda 400EX to life. This is alongside a single-phase, full-wave alternator with a rated output of 0.147 kW @ 5,000 RPM, which serves as its charging system.
Additionally, a sealed, maintenance-free 12V 8Ah/(10 HR) YTX9-BS battery powers electronic accessories. The quad requires an NGK DPR8Z or Nippon Denso X24GPR-U spark plug with a 0.6–0.7 mm (0.024–0.028 inch) gap.
Tires & Brakes
A 4/110 bolt pattern and stock rubber sizes – 22 x 7-10 M/R 101 Ohtsu tires at the front and 20 x 10-9 M/R 501 Ohtsu tires at the back – remain as is for the SporTrax. Replace the front tires with ITP Holeshot XC Sport ATV Tires (view on Amazon) in case of wear or damage. These radials are mounted on 10 X 5.5AT/9 X 8.0AT rims and mated to triple hydraulic discs (174-mm dual front discs and a single 220-mm rear disc) with dual brake calipers, making all-wheel braking possible.
Standard cold-tire pressure for all tires is 27 kPa (0.275 kgf/cm2, 4.0 psi) ± 15%. Staying within the range of 23 kPa to 31 kPa is allowable when airing down or inflating tires. A tread depth of 3/16 inches (4.0 mm) indicates a need for tire replacement.
Suspension
Enclosed in a double-cradle steel frame are independent, front double-wishbone and a Pro-Link rear swingarm, offering 209 mm and 230 mm wheel travel, respectively. The front has 5-way preload-adjustable Showa shocks, with the rear having a fully adjustable Showa mono-shock. The 48.4-inch/1,230-mm wheelbase and 3.2-meters/10.5-feet turning radius somewhat compensate for the miserly ground clearance of 4.3 inches (110 mm).
Dimensions
The TRX 400EX is compact at 72.2 x 45.3 x 43.7 inches (1,835 x 1,150 x 1,110 mm – L x W x H). Seat height is 810 mm/31.9 inches and accommodates medium-built to taller riders. The footpeg is 353 mm/13.9 inches off the ground and supports a more aggressive riding position – perfect for when the quad is not on the trails. Curb weight is 178 Kg (392 lbs.), while GVWR (Gross Vehicle Weight Rating) is estimated at 288 Kg (635 lbs.) – inclusive of the maximum load capacity of 110 Kg (243 lbs.) and full gas tank.
Exterior
2002 Honda 400EX plastics are not as flashy as those on succeeding models, but they do the job of keeping the engine and other vital components protected. Thankfully, owners can personalize their four-wheeler by availing a Kolpin ATV Rear Drop Basket Rack Collapsible Tailgate (view on Amazon) for more utility-oriented applications or an All Motor Graphics Wrap Kit (view on Amazon). In addition to the factory fenders, front cowl, and saddle seat, these racing decals will boost the aggressiveness and overall design of the SporTrax.
2002 Honda TRX 400EX Price
The 2002 Honda TRX 400EX was initially listed for $5,699, decreasing by $400 after two years. It was considered competitively priced at the time than the same-class competition. The SporTrax was straightforward and did not have special or hunter-inspired trims, helping keep it more affordable and appealing to the frugal consumer.
On the other hand, resale values average between $1,550 and $2,040 per Nada Guides data. About the same price range – from $2,045 to $3,000 – shows in auction listings and trader sites. These secondhand quads are often in decent working condition and primarily sell in the UK and North America. They are rarely sold for parts and mostly come with loads of aftermarket 2002 Honda 400EX parts like performance exhaust, air filters, and the like.
Honda 400EX Problems
While you can find a comprehensive troubleshooting guide in your service manual, here are the most known issues with the SporTrax for your reference:
Engine Won’t Start
Other than being an innate problem with the SporTrax, no-start issues are sometimes a result of increasing the bore of the 400EX. It would not matter if the upgrade came with Wiseco pistons (view on Amazon) or Hotcams. If done incorrectly or with a defective battery, the starting issue will still occur. It is fundamental to check on the state and charge level of the battery first before looking into the quad’s electrical or fuel system components to avoid this complication.
Brake Failure
This is not necessarily an issue for the 2002 model, but it has been hazardous enough to warrant a CSPC memo for product recall. 2000 – 2001 TRX400EXs were impacted, with 53 reports of incorrectly assembled brake pads received by the manufacturer. The faulty brake pads led to braking failure, potentially resulting in crash hazards and severe injuries. Honda saw to it that this factory miss was resolved for the 2002 Honda TRX 400EX.
Jammed-Up Axle
Despite the TRX400EX’s age, a rider should never feel jerkiness in the chain. The axle is likely jammed if this happens, primarily due to the axle carrier’s non-circular shape. Rolling the quad back and forth would help confirm if this is the case.
To fix this problem, loosen the four screws on the back of the swingarm holding the carrier in place. Next, stick something in the side slot to rotate the carrier and adjust the chain. There is a big axle nut on a threaded sleeve holding the axle in place. Confirm they are not backed off, causing slop in the rear-end and damage to bearings and other components.
Make sure to check if the bearings are shot or the carrier itself is in bad shape. If need be, aftermarket carriers with double row bearings are great replacements.
Other Issues
Minor problems to watch out for are head gasket leaks and electrical system faults, to name a few. Weak swingarms, engine overheating, and intermittent stalling, although reportedly an issue, are more a result of personal riding behaviors than the quad’s lack of reliability. Earlier SporTrax quads are more bulletproof than post-2005 ones, as evidenced by minor hiccups occurring more on later-year models.
About Honda
Honda Motor Company Ltd. is a Japanese conglomerate known worldwide for its ingenuity in automotive design and functionality. One of the pioneers of sport ATVs, the firm created the Honda 400EX in 2002 to revive the waning sport segment. Honda has made strides since its humble beginnings, mass-producing piston rings, surplus engines, and military aircraft automation into becoming the industry powerhouse it currently is.
Conclusion – 2002 Honda TRX 400EX Review
The 2002 Honda 400EX may not have received the GNCC-worthy upgrades it needed. But that dream is no longer as elusive as in yesteryears. With the multitude of performance-enhancing parts within reach, the SporTrax can easily transform into a serious trailer or a race-ready 4×4 and fulfill the whims of increasingly knowledgeable riders.
The fact that it remained unchanged throughout its production years is a blessing for present-day hobbyists and racing outfitters, as its starkness allows them to unleash the restrained potential of the four-wheeler. Moreover, retaining the quad’s simplistic form is proof of Honda’s incredible foresight into the modern ATV market and consumer behavior as a whole – not to mention an acknowledgment of the riding community’s appreciation and continuous elevation of the sport.
Kris is an avid off-roader and outdoor enthusiast who loves to brave the elements and take on challenging terrain. He also enjoys sharing his passion and knowledge with others so that they, too, can appreciate the ride.
About Kris