2003 Honda 400EX SporTrax Specs and Review 2022

2003 Honda 400EX: The 2003 Honda 400EX (a.k.a. TRX400EX also known as SporTrax) is now an iconic name among enthusiasts and enthusiasts. 

Its popularity is no surprise, as the 400-cc SporTrax has been considered by many as the best reliable and enjoyable quads available. 

2003 Honda 400EX

The rugged and striking design and style of this 4×4 brought pure-sport 4-strokes to the ATV world and offered thrills to the rider and lots more, as you’ll find out in this article.

The model of 2003 Honda 400EX (otherwise known as SporTrax) is part of the lineup of sport-ATVs that marked the revival of the sport-riding segment. 

It comes with an XR400R-adopted motor, 72-mph top speed rating, and Pro-Link front suspensions, it’s become popular among those who ride sport rec quads with a 4-stroke engine.

The simplicity, versatility, and pure-sport ergonomics are a few of the 2003 Honda 400EX’s key selling features. 

Read more about the specifications as well as the features and highlights of this big sport-riding machine in this article to find out more.

2003 Honda 400EX SporTrax

About the 2003 Honda TRX 400EX

The model of 2003 Honda 400EX marks the fifth installment in the Sportrax lineup since its introduction at the end of 1999. 

A machine that is sporty to its essence, the SporTrax’s devotion in bringing back the sport riding sector was a resounding call to its faithful followers. 

This caused being the Honda 400EX to get a reputation as a four-wheeler that is motocross-friendly.

Being the winner of this race Baja 1000 fresh out of the crate is a huge factor for this incredible achievement. 

The machine wouldn’t have achieved this if it wasn’t for the XR400R-inspired motor and other race-ready elements. 

The end result was that Honda intended for the model of 2003 to take on the MX/GNCC arenas along with the powerful 2-stroke rivals that are already on the scene of sport-ATV. 

However, due to the setbacks in design overall and a lack of features and tech enhancements, the machine was eventually put down as a tough trail tamer.

2003 Honda 400EX Specs & Features Engine

The 2003 Honda 400EX is brought to life by an air-cooled single-cylinder four-stroke engine. 

Piston displacement is 397 cubic centimeters (24.23 in3) The bore-stroke proportion is 85 x 70 millimeters (3.35 3.35 x 2.76 inches) while the compression ratio stands at 9.1:1. 

This power mill with a racing incline is equipped with the Radial Four-Valve Combustion Chamber as well as a 38-mm piston valve that is fitted coupled with the accelerator pump. 

The 38-mm carb is connected with urethane-foam oiled air filtration as well as dry-sump oil and also handles the air-fuel mixture.

Because the fact that the SporTrax engine’s design was derived from the XR400R, its design naturally leads to the 2004 Honda 400EX maximum speed of 65 to 72 miles per hour (105 – 112 km/h) and 28, RWHP (20.59 Kilowatts) horsepower. 

The engine is quite sturdy. However, you’ll have been able to alter the settings of your carburetor to high altitude rides above 1,000 meters or 3,000 feet.

Fuel & Lubrication

It comes with a capacity of 2.64 US gallon fuel tank capacity. Using fuel with the correct Octane level is crucial and can reduce (if not completely eliminates) spark knock. 

Eliminating contaminants such as dirt, dust, or water from entering the tank is also beneficial.

Engine pinging occurs due to the fuel mixture and air inside the engine cylinder that ignites in the wrong way. 

So, expect some pinging in the case of riding uphill or with loads that are heavy, since this could result in an incorrect ignition. 

However, consulting with a professional mechanic or immediately changing the fuel brands is highly recommended if you experience persistent pinging or during normal conditions of riding.

For engine oil, it has a capacity of 1.7 liters/1.8 US quarts (after draining) or 2.2 liters/2.3 US quarts (at disassembly) of SAE 10W-40 Pro Honda GN4/HP4 motor oil or equivalent. 

Other viscosity grades, SAE 5W,10W-30, 20W-40, or 20W-50 are allowed to be used following the ambient temperature. 

For optimal friction and lubrication, and without affecting the performance of the clutch make sure to use oils that have a minimum API grade of SJ+ that meets JASO the T903MA/MB standard. 

Do not use non-detergent castor-based or vegetable oils or engine oils that contain molybdenum or graphite additives.


Power is transferred to the ground using five-speed constant-mesh transmission as well as an operating, wet, multi-plate clutch (with the gearshift sequence 1-N-2-3-4-5) without reverse. 

An RK520 SMOZ10S or DID520V6 O-ring seal chain (96 or 120 links with a joint) can be replaced with the DID 520ERT3120RB or 520 ERT3 Exclusive Race Chain (view the full description on Amazon) It is able to handle wheel spin. 

Counter-balancers driven by gears minimize engine noise, which allows for easy maneuverability regardless of the terrain. 

Additionally, its fording depth limitation of 10 inches (25.4 cm) permits the quad to cross the shallow waters without difficulty.

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)


Placement of most of the controls – such as the clutch and parking brake levers, start button, headlight/dimmer/engine stop switches – are located on the left handgrip and has been this way for the majority of the 2003 Honda 400EX year models.

The fuel valve, gear pedal, and choke lever sit located on opposite sides of the motor. 

The throttle levers the front reservoir for fluid in the brake front brake, and the clutch lever is located in the handgrip on the left. 

In addition, the neutral lamp, as well as the ignition switch, are still in the center console and the rear reservoir of brake fluid and footpeg for the operator are located on the right of the four-wheeler.


An ICM (or Ignition Control Module) and an electric start system that operates at one of the fastest idle speeds of 1.400 100 RPM brings the 2003 SporTrax back to. 

One-phase (SCR shorted full-wave) alternator with a nominal power of 0.147 kW at 5000 RPM is the charging system.

It’s a non-maintenance 12-volt 8Ah/(10 HR) The YTX9-BS batteries have dimensions of 150x87x105 millimeters to power electronic accessories. 

It also requires a Nippon X24GPR-U or an NGK DPR8Z spark plug that has an 0.024-0.028 inch gap and torque specifications of 1/8 to 1/4 turns (old plugs) or 1/2 turn (new plugs) after the plug is seated. 

If you plan to ride for a long time, at high speeds change to the NGK DPR9Z spark plug or Nippon X27GPR-U spark plug.

Tires & Brakes

Front 22 7-10 M/R 101 20×10-9 rear 501 Ohtsu radials (each with an asymmetrical four-to-one bolt design) are mounted on aluminum or steel wheels. 

The knobbies are equipped with all-wheel-drive tri-hydraulic discs (174-mm discs in front and one 220-mm rear disc) with brake calipers that are dual which give the 4×4 a 70-30 percent ratio of stopping power. 

The front wheels have 10×5.5 AT mags and the rear wheels are 9×8.0 AT wheels (view the full list on Amazon). 

Aftermarket tires, such as Maxxis Razr four-ply Sport Rubber (view at Amazon) are great replacements for the stock rubber in the event of damage or wear.

2003 Honda

The cold-tire pressure in the front and rear should be at 27 kPa. Based on the type of terrain and the type of terrain, inflating or airing down tires in the range of 23 kPa-31 kPa is permissible. 

Regular inspection of tire tread is crucial, as any tread depth that is less than 0.1875 inches (4.0 millimeters) is a requirement for immediate replacement of the tire.


A Double-cradle frame made of steel (6.5deg angle for casters, 28-mm trails) is independent front double-wishbones with five-way preload-adjustable shocks and a ProLink rear swingarm that has an adjustable Showa mono-shock. 

Each set-up comes with wheelspin between 209 mm/8.2 inches and 230 mm/9.1 inches.

This is because the 48.4-inch/1,230-mm base of the wheel, 4.3-inch/110-mm ground clearance, and 3.2-meter/10.5-feet turning radius are the same as the models from previous years. 

Overall the suspension components help reduce the weight of unsprung as well as tighter cornering and enhance the traction.


Overall dimensions of the 2003 Honda TRX400EX measure 72.2×45.3×43.7 inches. The seat height is ideal for taller and medium-built riders at 810 mm/31.9 inches and is great for cutting across smooth surfaces. The GVWR is estimated at 635 pounds.

which includes the maximum capacity for a load of 243 pounds. The curb weight of 392lbs. as well as a full gas tank.


The 2003 SporTrax was among the models from the beginning that were yet to get the Team Honda-inspired graphics. 

The overall style is minimalist and ideal for customizing and is sturdy enough to protect the engine and the other internal components from elements.

The front cowl as well as the factory fenders can benefit from racing decals as well as third-party parts from 2003 Honda 400EX parts to add an element of dynamism for the four-wheeler.

2003 Honda 400EX plastics were available in yellow and red with the body matching, high-clearance fenders, and tough urethane skid plate that guard the wheeler’s bottom and rear brake-disc/sprocket. 

It is possible to keep these body parts as safe as you can by spraying washing them with running clean water with mild soap. Avoid using an electric hose, since it can cause abrasions that cause corrosion.

2003 Honda 400EX Price

In 2003, the Honda 400EX remained at its price at $5,699 on the list and was priced $400 lower than the MSRP of 2000. 

The competitive pricing provided the 400EX an advantage over similar-sized counterparts.

 It was also an appropriate choice for Honda’s part since practically nothing has changed in the structure and overall appearance. 

Similar to the production models of earlier in the year, the 2003 SporTrax only came with basic trims.

Perhaps, it was a way for this Japanese business to manage the price of the quad within a certain range.

In terms of resales values, prices vary between $1,805 and $2,375 according to Nada Guides’ information. 

Around the same price range – ranging from $978 to $3,000 – is displayed on the auction listing, Craigslist, and other trading websites. 

The majority of these used vehicles are in good, operating condition, and are typically offered within regions like the UK, California, Texas as well as North Carolina.

 Near-mint quads would naturally fall on the higher end of the price spectrum and come equipped with performance-enhancing add-ons, raising the average resale price by at least $500.

Honda 400EX Starting Issue

The bore increases, as well as the fuel and electrical system issues aside, a no-start problem is inherent to the ’03 Honda SporTrax. 

In most cases, the first thing you’ll observe is the starter motor trying to turn the engine but with no success. 

If this occurs, make sure you make sure the spark plug is tight and the engine stops the switch and battery, making sure that it is fully charging. 

Also, check whether any modifications to the bore were completed and if the modification was done properly. 

If these components fail to function you are able to begin examining other components to determine whether the problem is caused by fuel starvation, flooding in the engine, or another kind of malfunction.

Other issues to look out for are leaks in the head gasket and a flimsy swingarm. They can also cause overheating as well as periodic slowing. 

The gearbox and clutch are known to cause problems, especially for quads that have been heavily modified or for race applications. 

The tires that are standard are not as resistant to damage or punctures as owners would prefer. 

Most of the time this is due to lifestyles and habits of driving and does not necessarily indicate that the 4×4 falls short of its endurance. 

Fortunately, your manual for service contains pertinent information about how to handle the issues.

About Honda

Honda Motor Company Ltd. is a Japanese company that is known around the world for its innovation in automobile design and is a major player in the motorcycling and ATV industries. 

In 1937, it was established as Tokai Seiki, or Eastern Sea Precision Machine Company, Honda was originally a Toyota distributor of piston rings that were mass-produced.

Since that time the Japanese company has made significant strides in expanding its product line to include surplus engines motorized bicycles mini pickup trucks and then eventually incorporating ATVs such as the Honda 400EX in 2003. Honda 400EX.

 2003 Honda 400EX Review

Conclusion – 2003 Honda 400EX Review

It took two more years to wait for Honda to release its 2004 Honda 400EX suspension improvements. 

Even then the four-wheeled vehicle wasn’t at the end of the line for GNCC-approved changes. 

Many old-timers might think that the company’s stance of restraint caused worse harm than benefit. 

However, for those with more of an understanding of the next generation, this quad’s brutality definitely gave us, the owners, more liberty to customize the vehicle to be their personal. 

Professionally trained operators, as well as casual riders, admit that being able to modify a machine’s appearance can significantly enhance the riding experience, whether it’s on paths that are wooded or with hard-packed surfaces.

How fast is a 2003 Honda 400EX?


The model 2003 Honda 400EX (otherwise known as SporTrax) comes from the line-up of sport-ATVs that signaled the revival of the sport-riding segment. It comes with an XR400R-adopted motor, 72-mph top speed rating with ProLink back suspension. It’s now the most popular sports rec 4-stroke quads.

Does a 2003 Honda 400EX have reverse?

From neutral, with the quad running, reach down and pull the lever up and back. Then, after a second shift, It should pass first before going into reverse. It’s a sweet thing, and it does feature reverse.

How much does a Honda 400EX weight?

The 400EX could accommodate two people, a driver, and an additional passenger. It had a curb weight of 405 pounds when the 2.6-gallon fuel tank was filled.

Is Honda 400EX fast?

Registered. The standard Blaster has a speed of around 55mph, and a 400ex that is stock should be about 65mph. In drag, the Blaster should maintain its speed until the Honda is in higher gears and then should begin to pull away. As you sign, your Honda has standard gearing and an enormous bore kit.

What is the 400EX top speed?

In general, when it is fresh out of production, the 300 could range from 65 to 70, and most drivers get 68 as the maximum speed.

How much horsepower is a 400EX?

How Much Hp Does A 400Ex Have? The engine’s output in the 400EX model is between 250 and 30,000 horsepower…

Is the Honda 400EX 4 wheel drive?

Fast and aggressively styled, This wheeler marked the return of the sport-ATV category and the beginning of quads with four strokes. The 2004 Honda 400EX (a.k.a. the Sportrax 400EX) is an all-sports 4×4 responsible for the revival of the segment Sport-ATV.

How big is a Honda 400EX gas tank?

The vast 5.5G tank holds 5.5 gallons (20.9 Liters) of fuel for off-road adventures or long journeys. The extra capacity lets you travel farther between stops and prevents you from being stranded in the tails.

What was the last year Honda made 400EX?

The vast 5.5G Tank holds 5.5 gallons (20.9 milliliters) of fuel to go on those off-road adventures or longer journeys. The additional capacity lets you go farther between stops or prevent your vehicle from becoming stranded on the tails.

What is the best year for Honda TRX450R?

An ATV I would highly recommend would be the 2005 Honda TRX450R. Honda is a very well-known brand, and since this is their primary 450cc ATV, you will see a lot of them at the races. When it was first made available, the TRX450R was considered the most premium ATV for sport on the market.

What is the fastest side-by-side ATV?

The RZR XP 4000 power is leading the machine category, with the most potent engine available in a 4-passenger side by side. With 107 HP, it offers the highest speed of all UTV side-by-side.

Does the 2003 Honda 400EX have reverse?

From neutral, with the quad running, reach down and then move the lever forward and back. Then, after a second shift, It should pass first, then into reverse. It’s a sweet thing, and it does feature reverse.

Does a 2007 Honda TRX 400ex have reverse?

Heavy-duty clutch features 2mm-thick plates built to withstand the rigors of sport-ATV demands. High-efficiency oil cooler complements the tank’s capacity to provide the highest level of engine cooling. Five-speed transmission with Reverse includes the gears, ratios, and gears specially designed to be used for ATV sports use.

How many gears does a 300EX have?

This 5-speed transmission moves smoothly and offers great gearing for tight trails and demanding track work. The only thing riders were not thrilled with regarding 300EX 300EX was the absurd reverse engagement, which requires yoga movements to be activated.

2003 Honda 400EX FAQ

1. How much HP does a 400EX have?

A stock 400ex produces between 25 and 28hp…

2. How fast does a 400EX go?

A typical 400ex will run between 106 and 112 km/h. It could take a stocker some time to reach that speed but it’s pretty close to what they do.

3. Does the 2001 Honda 400EX have a reverse?

The production quads provided by the major OEMs may be a bit tamer than their Pikes Peak machines, but they’ll still put a look on any hardcore off-roader. … Every one of these quads is equipped with a reverse gear and a majority of them come with electronic starters.

4. Did Honda stop making 400EX?

Honda discontinued the 400EX as well as TRX450R models.

5. How much horsepower does a 2004 Honda 400EX have?

With the RFVC (Radial Four Valve Combustion Chamber) as well as an XR400R power mill that was adopted the 2005 Honda 400EX supports a top speed of 72 mph (116 km/h) and power output at 28 RWHP (20.59 kW).

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