Honda 400 EX Top Speed

Unbelievable Speed Records: Honda 400EX Top Speed Explored

Honda 400 EX Top Speed

Honda 400EX Top Speed

The Honda Motors Company introduced the remarkable Honda 400EX, an all-terrain vehicle (ATV) that made its debut in 1999 and continued to captivate enthusiasts until 2009. This quad featured a robust 28 horsepower engine that powered it to an impressive top speed of 72 MPH, delivering a thrilling experience for riders. Its sturdy steel frame, coupled with a removable sub-frame and rigid cast aluminum swing-arms, provided both durability and maneuverability, ensuring a dependable ride across various terrains.

One of the standout features of the Honda 400EX was its triple disc brakes, offering impeccable stopping power and enhancing overall safety. The ATV’s aggressive body style not only contributed to its striking appearance but also optimized aerodynamics, making it a visual and performance-oriented masterpiece. The well-engineered drive line and high-performance components of the Honda 400EX were meticulously designed to harness its capabilities fully.

Also Read: Honda Pioneer 700 Top Speed

Under the hood, the Honda 400EX boasted a 397cc dry-sump, air-cooled, four-stroke single-cylinder engine that incorporated innovative engineering elements such as the radial four valve combustion chamber (RFVC) and precisely tuned camshaft timing. These enhancements optimized torque delivery and ensured usable horsepower across a broad range of RPMs. The incorporation of dual intake and dual exhaust ports further contributed to the engine’s efficiency, ultimately enhancing the ATV’s overall performance.

The Honda TRX400EX was equipped with a five-speed transmission system that not only facilitated seamless gear changes but also featured a reverse gear, adding to the vehicle’s versatility. This feature-packed arsenal of go-fast components made the Honda 400EX a force to be reckoned with in the world of all-terrain vehicles, embodying Honda’s commitment to engineering excellence and high speed performance.

Honda 400EX Specs

Here are the Honda 400EX Specs presented in the form of a table.

Specification Value
Years Made 1999 – 2009
Model Name TRX400EX
Engine RFVC, dry-sump, 1-cylinder, 4-stroke
Displacement 397 cc
Bore and Stroke 85 x 70 mm
Carb 38 mm piston-valve with accelerator pump
Cooling Air-cooled
Starter Electric
Clutch Manual
Transmission 5-speed with reverse
Final Drive O-ring-sealed chain
Ignition CD with electronic advance
Suspension Front Independent double-wishbone with Showa shocks, 5-position spring-preload, 8.2 inches of travel
Suspension Rear Pro-Link fully-adjustable single Showa shock, with 9.1 inches of travel
Brakes Front Dual hydraulic 174 mm discs
Brakes Rear Single 220 mm disc
Tires Front 22 x 7-10 knobby radial
Tires Rear 20 x 10-9 knobby radial
Top Speed 72 MPH
Length 72.2 inches
Width 45.3 inches
Height 43.7 inches
Wheelbase 48.4 inches
Horsepower 28 HP
Seat Height 31.9 inches
Turning Radius 10.5 feet
Ground Clearance 4.3 inches
Weight 375 LBS
Fuel Capacity 2.6 gallons including 0.4 gallon reserve
Colors Black, Red
Top Speed (Again) 72 MPH
1999 Specs Virtually unchanged through 2009


The Honda 400EX ATV stands as an unwavering testament to Honda Motors Co.’s commitment to crafting exceptional off-road machines. An undisputed enthusiast choice, this model has not only earned its place in the hearts of ATV aficionados but has also emerged as a coveted gem in the ever-growing collectible market. Boasting an amalgamation of attributes that redefine the off-road experience, the Honda 400EX ATV seamlessly combines the elements of fun, reliability, and sturdiness.

One cannot delve into the world of Honda 400EX specs without acknowledging its legacy intertwined with the TRX 450R ATV model. Serving as an evolution of its predecessor, the TRX 450R, the Honda 400EX showcases a meticulous production process that upholds Honda’s commitment to excellence. The year 2009 marked a significant milestone for the EX 400 series, a year in which the ATV world witnessed the dawn of a high-performance contender.

At the heart of the Honda 400EX’s prowess lies its association with the high-performance TRX 400ex parts. These components, meticulously engineered to push the boundaries of performance, have transformed the ATV landscape. As a result, the Honda 400EX ATV emerged not only as a runaway hit in the market but also as a coveted item in auctions, classified sites, and ATV parts resellers. The fervor surrounding this model’s parts speaks volumes about its enduring legacy and the fervent following it commands.

Honda 400EX Piston Sizing and Overbore

The piston size in 400ex engines varies depending on the specific engine, natural wear, and cylinder boring done to increase engine displacement. The standard piston diameters and corresponding engine displacements for 400ex engines are:

  • 85.00mm piston = 398cc (standard)
  • 85.50mm piston = 402cc
  • 86.00mm piston = 407cc
  • 87.00mm piston = 416cc
  • 88.00mm piston = 426cc
  • 89.00mm piston = 435cc

These piston sizes can change over time due to natural wear. If you measure your piston opening and find it to be 85.35mm, it is likely an 85.25mm 400cc engine that has been overbored by 0.10mm. When rebuilding, select the appropriate 400ex piston size and piston rings based on your measured opening.

Additional information about the Honda 400EX ATV

When delving into the world of all-terrain vehicles (ATVs), the Honda 400EX stands out as a name that resonates with enthusiasts and riders seeking exhilarating experiences. As part of the Sportrax lineup, the Honda 400EX ATV captures the essence of both thrill and reliability. Its popularity stems not only from its powerful performance but also from its beginner-friendly nature, making it a comfortable choice for riders of varying skill levels.

One of the standout features of the Honda 400EX is its design tailored to cater to ATV enthusiasts who seek adventure on the track and trails alike. The ATV’s capability to handle jumps and wheelies with finesse is a testament to its robust construction. This versatile package ensures that both adrenaline junkies and those looking for a comfortable ride can find their perfect match in the Honda 400EX.

Speaking of performance, the Honda 400EX boasts a noteworthy factor that enthusiasts truly appreciate—the top-notch clutch system. This factor plays a pivotal role in delivering power to the wheels efficiently, making it an ideal companion for tackling tricky terrains and daring maneuvers. The inclusion of a reverse gear is a thoughtful addition, allowing riders to navigate in tight spots or correct their direction without hassle.

Beyond its prowess on the trails, the Honda 400EX also addresses the practical side of ATV ownership. Repairs and maintenance are integral considerations, and this ATV doesn’t disappoint in that aspect. Its design incorporates elements that ease repairs, ensuring that riders can get back to their adventures swiftly. This commitment to user convenience is part of what sets the Honda 400EX apart in the realm of ATVs.

Despite its many strengths, it’s important to acknowledge that every machine has its downsides. In the case of the Honda 400EX, some riders might find the reverse gear’s functionality a bit different from the conventional forward drive-train. However, this design choice doesn’t overshadow the overall positive experience the ATV offers.

Honda 400ex Top Speed

In the realm of off-road enthusiasts and ATV aficionados, the Honda 400EX stands as a symbol of unparalleled performance and durability. Even in its stock form, this ATV radiates prowess, often found in brand new condition, ready to dominate any terrain it encounters. At the heart of the Honda 400EX’s allure lies its impressive top speed of 72 MPH, a feat that leaves a trail of excitement on both pavement and rugged landscapes alike.

For those who seek to push the limits further, coaxing out every ounce of power becomes an irresistible urge. This drive for supremacy has led to a market brimming with performance upgrades that can transform the 400EX into an unrivaled powerhouse. The integration of Elka shocks and ITP bead-locks, for instance, adds a touch of finesse and tenacity to its already formidable persona.

While the allure of brand new ATVs is undeniable, the realm of used 400EX quads unveils a distinct facet of value. Their durability and performance continue to shine through the test of time, often leaving enthusiasts astonished by their enduring capabilities. Moreover, the avenue for customization further elevates the 400EX’s standing, allowing riders to tailor their experience to exacting specifications.

Renowned as one of the best ATVs ever made, the Honda 400EX has earned its title through unrelenting competition and triumphant victories. It proudly stands as a champ in a league of its own, consistently securing the top spot on the ATV Brands page. The TRX400EX model encapsulates the pinnacle of Honda’s engineering prowess, a testament to its enduring popularity and unwavering prowess.

In the realm of ATV enthusiasts, the Honda 400EX reigns supreme, a true champ that has etched its name in history through its exceptional performance and enduring popularity. This ATV embodies the essence of Honda’s legacy and mastery, securing its position as an icon in the hearts of riders and on the trails where it roams.

Honda 400ex Oil Type and Capacity

When it comes to optimizing the engine performance of your Honda TRX 400EX ATV, choosing the right oil is paramount. One of the highly recommended options is the 10w40 ATV oil. This oil type has been specifically designed to cater to the demands of high-performance ATVs like the TRX 400EX. Its viscosity ensures proper lubrication across a range of temperatures, providing excellent protection to your engine components.

Speaking of oil capacity, the Honda TRX 400EX requires 2 quarts of oil to operate at its best. It’s essential to adhere to this requirement for optimal performance and longevity of the engine. Maintaining the right oil level ensures that all internal parts are properly lubricated, minimizing friction and wear.

For those who are looking to enhance their ATV’s performance even further, using fully synthetic oil can make a notable difference. Fully synthetic oil offers superior lubrication and temperature stability compared to conventional oils. It’s engineered to withstand high stress and extreme conditions, which is particularly beneficial for an ATV like the TRX 400EX that might be subjected to intense off-road adventures.

In the world of ATVs, like the Honda TRX 400EX, aftermarket parts play a significant role in customization and performance enhancement. Alongside the oil choice, aftermarket parts can contribute to boosting the overall capabilities of your ATV. These parts are designed with specific performance goals in mind, allowing enthusiasts to tailor their vehicles according to their preferences.

How Fast Does a Honda 400EX Go?

The manufacturer states that the Honda 400EX is capable of reaching speeds between 65 and 72 miles per hour. But most riders report that the typical maximum speed they achieve on this model is around 68 mph. A number of variables can affect the actual top speed, such as the riding terrain, the production year, and any customizations done to the ATV. Overall, while the 400EX is rated for 65-72 mph, the common experience is a peak speed of about 68.

How Many Miles Can I Get Out of Honda 400EX?

The lifespan and total mileage you can expect from your Honda 400EX ATV will vary based on several factors. There is no singular answer that applies to every rider and usage situation. Proper maintenance and care are key to maximizing the performance and longevity of your 400EX. With consistent upkeep and servicing, it’s possible to accumulate over 10,000 miles or 16,093 kilometers on this model.

The type of riding you do, how often you ride, and how well you take care of your 400EX will impact how long it lasts and how many miles you can put on it. The bottom line is that by following recommended maintenance schedules and avoiding excessive wear and tear, you can get many miles and years out of your Honda 400EX with the right riding habits and care.

Avoid Difficult Trails

Riding ATVs can be thrilling, but constantly pushing them to the limit on rough terrain will accelerate wear and tear. As the saying goes, moderation is key. To extend the life of your ATV, use discretion and limit aggressive riding on harsh trails. Opt for lighter terrain whenever possible – it’s an easy way to keep enjoying your ATV while avoiding premature damage from overuse. The goal is balance – have adventures, but be mindful about preserving your machine so the fun lasts.

Use High-Quality Fuel

Using poor quality or contaminated fuel can negatively impact the performance of your Honda 400EX. For optimal operation and longevity, it’s best to avoid old or dirty gasoline. Instead, use only fresh, high-quality fuel to keep your machine running smoothly. Sticking to the recommended fuel grade will help prevent issues caused by low-grade gasoline. With the right fuel, your 400EX will maintain peak performance and reliability for miles to come. The key is being selective at the pump to safeguard your investment.

Proper Tire Care

Proper tire maintenance is critical for your Honda 400EX’s performance and safety. Tires in good condition provide vital traction across different riding terrains. Make it a habit to regularly inspect your tires for any visible damage or excessive wear. Catching issues early prevents more significant problems down the road. Well-maintained tires will let you maneuver confidently during your adventures. Don’t overlook this important component – take the time to check your tires and address any concerns before hitting the trails. Good tires equal better handling.

Watch Your Gear Selection

Proper gear selection is key to optimizing your Honda 400EX’s performance. Use low gears when riding up steep inclines.

The increased torque enables you to power up slopes more easily. On flat surfaces, higher gears allow smooth acceleration and greater top speed.

To get the most out of your 400EX, pay close attention to terrain conditions and choose the appropriate gear.

Low gears for conquering climbs.

High gears for flat out speed. Matching the gear to the situation will let you handle various trails and surfaces confidently. Mindful shifting equals maximized performance.

Routine Maintenance

Performing regular maintenance is one of the simplest ways to extend the life of your ATV. Be sure to periodically inspect and replace air filters when needed. Check tire pressure routinely. And change the engine oil regularly. Following basic maintenance procedures will maximize your ATV’s mileage over time. Small habits like replacing filters, minding tire pressure, and oil changes will go a long way in preserving performance and avoiding costly repairs down the road. Consistent upkeep is the key to reliable long-term operation.

How Much Power Does A Honda 400EX Have?

The Honda 400EX is powered by a potent 397cc four-stroke engine, producing a peak of 34 horsepower. This generous output delivers robust torque and acceleration, enabling the 400EX to capably cover long distances and handle rough off-road conditions. The ample muscle under the hood gives the 400EX excellent power-to-weight ratio and nimble handling.

This combination of brawn and agility is what makes the 400EX a top performer, explaining its popularity among ATV riders seeking thrilling capability from their machine. With its strong engine as a foundation, the 400EX brings power and endurance together in one proven off-road package.

How to Improve the Honda 400EX Top Speed?

While the Honda 400EX’s factory top speed is 72 mph, some riders seek even greater velocity. For those wanting more rip from their 400EX, there are effective ways to safely coax out additional speed:

Upgrade Your Performance Exhaust System

Swapping the stock exhaust system for a high-performance one can significantly boost your ATV’s capabilities. Installing a free-flowing exhaust enables your engine to inhale more easily, generating extra horsepower and torque. The improved airflow and power output enhance your 400EX’s speed and acceleration.

Modify the Air Intake System

The standard air intake setup on a Honda 400EX consists of an air filter and air box. These parts allow clean air to go into the engine, which determines the amount of fuel the engine gets. Ultimately, this impacts the average speed and power output of the 400EX.

Replacing the stock air filter with a high-flow air intake filter permits more air to enter the engine. Since more air is moving in and out of the engine, it can achieve higher speed and power.

Try Rejetting the Carburetor

In addition to modifying the exhaust and air intake, you must also boost fuel flow to properly align the air-to-fuel ratio for optimal performance. The most effective method to increase fuel flow on a Honda 400EX is to re-jet the carburetor.

Rejetting involves replacing the carburetor jets with different sized jets so the engine receives the proper fuel amount. To maximize performance, consider new pilot and needle jets. Only a tuning adjustment is needed for the main jet.

Switch to High-Performance Tires

The wheel tires are another component that may need upgrading to reach higher speed levels on your machine. For optimal results, consider replacing the stock tires with aftermarket high-performance tires. High-performance tires can provide enhanced grip and traction, ensuring stability at top speeds. Additionally, premium tires offer superior control and stability, improving the overall riding experience. With better grip and control, high-performance tires allow you to fully utilize your machine’s speed capabilities.

Cut the Weight

The lighter the total weight of your Honda 400EX, the better it can perform. Therefore, consider substituting heavier components like the suspension and wheels with lighter alternatives to reduce the ATV’s overall weight. This provides an improved power-to-weight ratio, quicker acceleration, and higher top speed.

However, if modifying your 400EX for increased speed, be mindful of local laws and speed limits. Also, understand that speed modifications can alter normal function, so get accustomed to the changes in a controlled setting before road use.

Lastly, have an experienced mechanic or ATV expert perform the installations to ensure proper modifications for optimal performance. Their expertise will help maximize your upgrades while staying compliant and safe.

Pros & Cons of Honda 400EX

Pros Cons
Nearly flawless engine with minimal mechanical issues. Early models’ wiring harness behind headlights prone to wear and shorts.
Reverse setting in 2005+ models aids in trail riding and tricky situations. Factory front shocks are the weak point in the otherwise solid suspension; suggests upgrading to 450r shocks.
Compact size fits easily into pickup trucks. Rear grab bar is integrated into subframe, making replacement impossible; owners often attach modified bars.
Exceptional handling, ideal for trail riding. Occasional ticking sound while riding indicates necessary valve adjustment or timing chain replacement.
Outstanding balance for wheelies. Swing-arms susceptible to cracking when landing on hard surfaces during jumps.
Upholds the reputation of “Hondas don’t break. Power and speed on flat surfaces are not particularly impressive.
Abundant affordable aftermarket parts.


The specifications of the Honda 400EX all-terrain vehicle are revolutionary. This ATV delivers an exciting riding experience, whether you desire high-speed thrills or casual off-road journeys. While its maximum speed is approximately 72 miles per hour, modifications like upgraded exhaust and air intake, rejetting the carburetor, reducing weight, and installing high-performance tires can push past this limit. With its game-changing features, the 400EX promises memorable rides on any terrain.

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