2004 Honda 400EX Sportrax Specs and Review 2022

2004 Honda 400EX Sportrax: From one of the longest-running ATV lineups the Honda 400EX of 2004 Honda 400EX (a.k.a. TRX400EX (also known as Sportrax) was a significant moment in the evolution of sport quads. 

Fast and aggressively styled, this wheeler marked the return of the sport-ATV market and the first quads with four strokes.

2004 Honda 400EX Sportrax

(a.k.a. the Sportrax 400EX) is a pure-sport 4×4 which is the reason behind the revival of the sport-ATV segment. 

It is equipped with a 397-cc XR400R-inspired motor, Pro-Link rear suspension, 72-mph top speed, and a slick design The 4×4 continues to be a dominant force in the modern ATV market.

With its victory over its first Baja 1000 out of the start, The Honda 400EX bravely put an end to the repercussions from the 1988 Consent Decree, eventually paving the way for the racing 450cc quads we have today. 

Read this article to discover more information about the specs along with the notable features, and how this groundbreaking machine changed the world of sport-ATVs forever.

2004 Honda 400EX Sportrax

The 2004 Honda Sportrax(r) TRX 400EX

This year’s Honda 400EX is the 6th installment in the class 400 Sportrax lineup that was first released in 1999. 

While not as powerful as today’s speedsters with 450cc this machine that was pure-sport has been the catalyst for the revival of the sport-quad race just after the 10-year ATC Ban suffered by manufacturers all over the world.

In a significant way, the Sportrax brought back the community of riders’ interest in sport riding.

The Game Changer

While the majority of companies were cautious to avoid triggering yet another Consent Decree, Honda was in the process of developing the next generation of ATVs that had four strokes. It’s true that 2-strokes are widely available on the market. 

However, should the Japanese firm has any lessons to learn from the past 10 years automobile regulations will continue to become more stringent and competition will only get stronger.

With these new issues to consider, Honda decided to address the demand from consumers for a brand new vehicle that would satisfy the desires of racers who are looking for thrills as well as recreational cyclists. 

The XR400R was the first to receive acclaim from critics, Honda decided to use its power unit as the basis for the TRX 400EX. 

In the end, a victory over this challenge, the Baja 1000 fresh from the warehouse further demonstrated how well this engine performed using a completely revamped ATV frame.

2004 Honda 400EX Specs & Features Engine

An impressive 397-cm3 (24.23 inches) RFVC air-cooled single-cylinder 4-stroke engine with a bore-stroke proportion of 85 x 70 millimeters (3.35 3.35 x 2.76 inches) The Sportrax TRX400EX engine comes to life. 

A 38 mm piston valve fitted with an accelerator pump controls the mixture of fuel and air, and it mates to the compressive ratio of 9.1:1 and dry-sump Lubrication.

Thanks to the RFVC (Radial Four Valve Combustion Chamber) as well as an XR400R power mill that was adopted The Honda 400EX of 2004 Honda 400EX supports a top speed of 72 mph (116 km/h) and a maximum horsepower at 28 RWHP (20.59 kW). 

Some people find the low-end torque insufficient, but changing the ratios to 14/38,15/39, or 14/39, and then adding the Dynatech CDI box will provide the power you require.

Fuel & Lubrication

The capacity of the fuel tank will be 2.64 US gallons/10 liters (inclusive of reserve of 0.42-US gallon/1.6-liter reserve) of gasoline that is unleaded with an optimum PON 92 rating, which contains at least 5percent MTB (Methyl Tertiary Butyl Ether) and 10 percent ethanol, or less than 5 % methanol.

In terms of the engine oils, Honda advises 1.7 Liters (1.8 US quarts – after draining) of SAE 10W-40 oil or equivalent. 

To get the best performance, choose Pro Honda HP4 or GN4 motor oils that have the API quality of SJ+ (without molybdenum or graphite additions) that meet JASO T903 MA requirements.

To avoid spark knock, don’t make use of gasoline with lower octane levels. However, a slight pinging is not a cause for concern when you are riding on your Honda 400EX in 2004 Honda 400EX on a climb or with an intense burden. 

However, if it occurs in normal conditions of riding and at a steady speed make sure to change the fuel brand immediately. See a professional mechanic if engine pinging continues to occur.


A constant-mesh five-speed transmission and an electric, multi-plate cable clutch assembly (with the pattern of a 1-N-2-3-4-5 shift) provide energy to the ground. 

The DID520V6 (or the RK520 or RK520(view at Amazon) SMOZ10S O ring-sealed chain (120 links and a joint) manages wheelspin.

It features a counterbalancer driven by gears that dampens engine vibrations and contributes to smooth operation. Additionally, dual exhaust and intake ports allow for optimal efficiency of the engine when riding in more challenging conditions. 

In this reverse feature, it was added to the Sportrax in 2005 along with other powertrain improvements.

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)


Most of the controls, such as the clutch and parking brake levers, start button, headlight/dimmer/engine stop switches, are near the left handgrip. 

The choke lever, fuel valve, and gear pedal are located on the left-hand side of the motor.

The front reservoir for brake fluid, the front throttle lever, and the brake are located near the handgrip that is to the right. 

A neutral-indicator lamp, as well as the ignition switch, are located on the central console just above the cap for the fuel tank.

2004 Honda


A system for electric starting as well as the ICM (or the Ignition Control module) brings life to the 2003 Honda 400EX.

Single-phase (SCR shorted fully-wave) output alternator that has a maximum power of 0.147 kW at 5,000 RPM acts as an electric charging device for this quad. 

The system requires NGK DPR8Z as well as a Nippon Denso X24GPR-U spark plug that has an 0.6-0.7 millimeter (0.024-0.028 millimeter) gap as well as a 12-volt 8Ah/(10 HR) YTX9-BS battery (view on Amazon) with dimensions of 150x87x 100 mm (6.00 x 3.44 4.19 inches) 4.19 inches) to power electronic components.

Tires & Brakes

Stock rubber is comprised of 22 7-10 M/R 101 front tires and 20 10-9 M/R 501 rear Ohtsu radial tires sporting the 4/110 bolt pattern. 

The knobbies are connected to wheel-drive discs that are all-wheel driven (174-mm discs for the front and one 220-mm rear disc) with brake calipers mounted on all fours, giving the four-wheeler stopping power.

 The front tires sit on 10 x 5.5 AT mags, while the rear tires are placed located on 9 X 8.0 AT rims.

The front and rear cold-tire pressure recommendations are 27 kPa (0.275 kg/cm2, 4.0 psi) +15 percent. 

Don’t exceed the 23 kPa range (0.235 kg/cm2, 3.4 psi) to 31 kPa (0.315 kg/cm2, 4.6 psi) when you are airing down or inflating your tires. Check the tread regularly and change your tire when the tread is at a minimum of 3/16 inches (4.0 millimeters).


In a tubular steel frame, the frame and subframe, the front is an independent double-wishbones with five ways of preload adjustment Showa shocks as well as a Pro-Link rear swingarm with fully adjustable Showa mono-shock.

 Each configuration included wheels traveling in the range of 209 mm/8.2 inches (front) and 230 mm/9.1 inches (rear). 

The wheelbase of the vehicle is 48.4 inches (1,230 millimeters) and the minimum clearance for the ground was 4.3 inches (110 millimeters). The radius of turning can be measured at 3.2 meters/10.5 feet.

2004 Honda 400EX components like the rear swingarm made of cast aluminum and piggyback Showa shocks contribute to the quad’s remarkable performance and endurance. 

Additionally, the knobby tires and wheels made of aluminum help reduce the weight of unsprung in addition to improved grip and a more precise turning. 

If these benefits were not enough, subsequent models received further upgrades to the suspension.


The 400EX’s dimensions measure 72.2 x 45.3 and 43.7 inches (1,835 1150 1110 mm – L x W H). The seat has a height of 810 mm/31.9 inches and a footpeg size of 353 mm/13.9 inches.

 The dry weight of the seat is 170 kg (375 pounds. ) and the GVWR (Gross Vehicle Weight Rating) is estimated to be 288 kilograms (635 pounds.) 

comprising a fully loaded tank as well as the vehicle’s maximum load of 110 kg (243 lbs. ).


The Sportrax is on receiving new graphics inspired by Team Honda and it is now available in red-black and yellow in 2004 Honda 400EX plastics. 

A slick front cowl a narrow saddle seat and high-clearance fenders enhance the sporty four-wheeler’s design and ergonomics. 

In addition, the tough skid plates made of urethane shield the wheeler’s engine casing as well as the brake disc/sprocket in the back.

Cost of a 2004 Honda 400EX

The price list for this 2004 model of the TRX 400EX Honda is $5,299and rising only by $600 by 2009. The price is significantly lower than the 450 class equivalents that are available in the 4×4. 

The Sportrax was not equipped with any special edition trims available for the year in question, meaning that its value was constant regardless of the color of its body.

Auction listings, on the other hand, range between $1500 and $7,499. A majority of these vehicles come with lots of extras and can be located within California, Arizona, and Canada. 

Pre-loved quads in the $2,000 to $3500 price range usually come with aftermarket components such as Alba Racing pipe, paddle/dirt tires, K&N filter, Nerf bars, and brand new seats. There are also some rare (but more expensive) finders with only two or three former owners.

Sportrax 400EX Common Problems

Sportrax 400EX Common Problems

There are a few known issues associated with problems with the 2004 Honda 400EX that are similar to other ATVs and can be found in the engine or transmission as well as fuses, tires, and. 

There are solutions for these problems in the service manual. However, if you don’t have one use this article as a guideline:

Starter Motor Doesn’t Work

There are four possible causes that could be the cause of the issue, and they are worth examining All of them are electrical components. 

The most frequent cause is a malfunctioning engine stop or ignition switches as well as a damaged or corroded battery. 

The majority of owners notice issues in the fuse or the starter motor over time. In certain instances, it could be caused by the simplest of things like the starter motor not being in neutral while operating the gears.

Engine Won’t Start

You might notice that your starter motor trying to turn the engine however, it is unable to move. If this is the case it could be caused by a problem within one of the fuels or electrical system components. 

Make sure that the ignition plug as well as your battery haven’t become loose, and that your battery is fully charged. 

If the two aren’t in good condition then you’re most likely to experience an engine flood or run out of fuel.

Pinging / Rough Idling

Although a slight pinging can be tolerated when you are under a lot of loads or when you are on steep slopes, however, it shouldn’t occur any other time. 

If it does, you will have to either adjust the idle to spec or change your fuel to a manufacturer-recommended variant. 

In most cases, the steps mentioned above will resolve minor engine noise issues. If not, contact your local dealer to take a brief review of your quad.

Flat Tire

Tires that are damaged or punctured can’t be fixed, particularly since this year’s Honda 400EX model is popular for race applications. 

If it is, a quick solution is to fill the punctured region in the tire, until the area is able to have it repaired permanently or replaced. 

Depending on the extent and extent of damage you might have to replace the rims, too. In no way should you continue to ride with a flat tire to avoid the possibility of being involved in a crash.

Blown Fuse

The moment that one of your electrical components ceases to function is a must. This is the first thing you should check before you look elsewhere in your vehicle. 

You can check your fuse by removing your seat and the cover for the fuse case. Be sure to shut off your ignition before you look at your fuse, to prevent an unintentional short circuit.

In addition to the issues discussed above In addition to the above issues, the gearbox and clutch are a problem, especially when modified heavily which can be one of the weakest points on the Sportrax. The OEM head could be damaged and could require re-plating or a complete replacement.

About Honda

The Honda Motor Company Ltd. is a world-renowned pioneer in the motorcycle and ATV industries. It is also the brain of the 2004 Honda 400EX. 

The company’s headquarters are in Minato, Japan, Honda is widely acclaimed for its expertise in the field of automotive manufacturing, AI, and aerospace.

These are ventures that the company has only entered into in the past four decades. Internal combustion engines in particular speak of the humble beginnings of the company.

Conclusion – 2004 Honda 400EX Review

In 2004, the Honda 400EX held a lot of promise, as enthusiasts believed that the quad would receive further upgrades to ensure it was GNCC-compliant. 

However, this didn’t take place as its design was virtually unchanged through its last year. However, to classify its Sportrax 400EX as lackluster would be an oversimplification.

Its inability to compete on racing tracks for motocross does not render the 400EX less of an award-winning sports quad. 

Its absence of race-worthy enhancements diminishes its ability off-road. It’s actually these flaws that make it more appealing and noteworthy. What’s not to love about an imperfect quad?

How fast is a 2004 Honda 400EX?

72 mph

With RFVC (Radial Four Valve Combustion Chamber) as well as an XR400R power mill that was adopted, the Honda 400EX of 2004 Honda 400EX supports a top speed of 72 mph (116 km/h) and a horsepower of 28 RWHP (20.59 kW).

What is the specs on a 400EX?

The 400EX had a length of 72.2 inches, having a width of 48.4 inches and a total size of 45.3 inches. The seat was 31.9 inches higher than the floor, and at its lowest, the tube chassis of steel had a clearance of 4.3 inches. The 400EX could accommodate one driver as well as one passenger.

How fast does a TRX 400EX go?

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

How much horsepower does a 2004 TRX 450R have?

The TRX450R, a high-performance vehicle, was launched on the marketplace. Honda Powersports designed the TRX450R all-terrain car to appeal to the most demanding racer, as well as the non-competitive rider. ATV enthusiasts appreciate the performance of the four-stroke liquid-cooled engine that is 450cc and produces 33 horsepower.

Does 2001 Honda 400EX have reverse?

All of these quads feature Reverse gears, and a majority of them come with electric starters. Specific models, like the Polaris, are equipped with fully automated transmissions. You need to press the button and rock.

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 additional capacity allows you to travel farther between stops and prevents you from being stranded in the back.

How many quarts of oil does a 400ex take?

Be aware that the Honda TRX 400 uses 1.9 quarters in oil. Before filling it, make sure you know the engine’s capacity and remember that the entire oil won’t go into the tank simultaneously. Some fat will need to move through the crankcase to make room inside the oil tank.

How do you adjust the air fuel mixture on a 400ex carburetor?

It’s, in fact, an airscrew. The carb doesn’t have the air screw. If you rotate the screw clockwise, it will make it slimmer. Make it counterclockwise to make it richer.

What is the best year for Honda TRX450R?

One ATV I would suggest is one called the year 2005 Honda TRX450R. Honda is a well-known brand, and since this is their primary 450cc ATV, there are plenty of these on the race track. When it first launched in the year 2000, the TRX450R was considered the most premium sport ATV available.

Whats faster yfz450 or TRX 450r?

Registered. If you’re seeking “faster,” Id have to suggest that the Yfz is quicker than the 450r for the stock; however, after a few modifications, and gearing, it can be a beast.

What is a Honda 400EX?

It was first released in 1999. the TRX400EX was first released in 1999. It is an ATV produced by Honda that came with a dry-sump air-cooledSingle-cylinder four-stroke engine.

Is Honda 400EX automatic?

The 400EX included an Electronic CDI (capacitor discharge ignition) and an electric starter. Each 400EX transmitted energy to its rear axle through the chain-driven, five-speed manually operated transmission. This transmission also came with an reverse gear.

2004 Honda 400EX Sportrax FAQ

1. How fast is a 2004 Honda 400EX?

The 2004 Honda 400EX is powered by RFVC (Radial Four Valve Combustion Chamber), and an XR400R power mill. It has maximum speed support of 72 mph (116 km/h) and a horsepower of 28 PHP (20.59 kW).

2. Why does 400EX backfire?

A jet inside could have been clogged, not letting enough gasoline in. Clean your carb and see if it pops or backfires.

3. How fast does a Honda TRX 700 go?

Heavy-duty clutches are 2mm thick and can withstand the demands of sport-ATV use. A high-efficiency oil cooler complements the large-capacity tank to provide maximum engine cooling. The five-speed transmission with reverse has gears and ratios specially designed for ATV sports use.

4. How much oil does a 2004 Honda 400EX take?

The motor’s capacity is 1.95 cubes with a filter change Fill the oil tank with about 1 4/5 quarts of oil. You can leave the engine running at idle for a while, but be sure to check for any leaks.

5. How do you tell what year a 400EX is?

I don’t know the year because the sticker on my 400ex that I just purchased came off. I paid 50 dollars for it. The VIN number should be located on the front of your frame by the top bumper mount. Look at the 10th digit to see the year. That sticker is gone.

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