Honda 400EX Review, Top Speed, Specs & Price 2024

Honda 400EX Review

The legendary Honda 400EX sport ATV set the benchmark for performance when it was introduced in 1999. This revolutionary machine combined a high-revving 397cc engine with a lightweight, race-inspired chassis.

Even over 20 years later, the 400EX is still considered one of the greatest sport quads ever built. But does this discontinued ATV still stack up against modern rivals?

This in-depth 400EX review will cover everything you need to know:

  • Overview of the 400EX model history
  • Engine, transmission and performance specs
  • Key features and innovations
  • Handling, capabilities and customization
  • Reliability, maintenance and repair costs
  • Ownership pros and cons
  • Used pricing and availability
  • Top alternatives to consider

After reading through this comprehensively detailed review, you’ll know if the legendary Honda 400EX is still worth buying used or if you’re better off with a more modern sport ATV. Let’s hit the trails!

400EX Model History Overview

The 400EX was introduced for 1999 as a successor to the immensely popular 300EX. Building upon the 300’s winning formula, the 400EX upped the ante with a larger high-revving engine, improved suspension, updated styling and more.

Here’s an overview of the 400EX generations:

  • 1999-2000 – Debut years for the 400EX. Offered great performance from its 397cc engine but lacked independent rear suspension.
  • 2001-2002 – Upgraded with Honda’s innovative Independent Rear Suspension (IRS). This substantially improved handling and ride comfort.
  • 2003-2009 – Remained largely unchanged aside from new color options. Continued to be highly sought after for its bulletproof reliability.
  • 2009 – The final model year for the 400EX before being discontinued in 2009, ending an impressive 11 year production run.

Even though the 400EX has been out of production for over a decade, it remains a highly desirable sport ATV on the used market. It set the benchmark for delivering more power and sharper handling than rivals like the Yamaha Blaster and Suzuki LT250 QuadSport.

Key Specifications For The Honda 400EX

SpecificationsHonda 400EX
Engine397cc air-cooled single-cylinder four stroke
Bore x Stroke85mm x 70mm
Compression Ratio9.2:1
ValvetrainSOHC, two valves per cylinder
Fuel SystemTwo Keihin 32mm carburetors
IgnitionCD with electronic advance
StartingElectric start
TransmissionFive-speed with manual clutch
Final DriveO-ring chain
Front SuspensionIndependent double wishbone, 8.1 in travel
Rear SuspensionSwingarm with single shock (1999-2000) / Independent double wishbone, 7.3 in travel (2001-2009)
BrakesFront: Mechanical drum/disc, Rear: Mechanical drum
TiresFront: 20 x 7-10, Rear: 18 x 10-8
Wheelbase48.8 in
Seat Height31.9 in
Ground Clearance4.3 in
Fuel Capacity2.6 gallons
Curb Weight395 lb
Max Load Capacity350 lb
Towing CapacityN/A
Top Speed (stock)72 mph
ColorsRed, Yellow, White/Red

Honda 400EX Engine Performance Specs

The star of the show is the 400EX’s 397cc air-cooled single-cylinder four-stroke engine. This compact powerplant utilized lightweight aluminum construction and a forged piston.

It was tuned to deliver an incredibly wide powerband with plenty of top-end pull. Peak output was 28 horsepower at 8,500 RPM, allowing it to spin up to an exciting 9,500 RPM redline.

This high-revving design provides energetic acceleration whether you’re blasting out of corners or hitting massive jumps. Power is transferred to the wheels via a five-speed manual transmission with manual clutch.

The 400EX engine proved remarkably durable, with most exceeding 30,000 miles without needing a rebuild. Keep in mind that excessive time at wide-open throttle can shorten engine life. Still, these motors are built to handle the demands of high RPM sport riding with proper maintenance.

Honda 400EX Top Speed & Acceleration

So how fast could the 400EX go flat out? Stock 400EX top speed is around 72 MPH on a flat surface. However, the 400EX really excels in acceleration and mid-range punch.

It can rocket from 0 to 30 MPH in under 2 seconds thanks to the explosive low-end and mid-range power. And the lightweight feel makes the 400EX seem even quicker as it begs you hold the throttle pinned.

Of course, top speed can be increased substantially by modifying the gearing and adding engine performance modifications. It’s not uncommon to see built 400EX quads exceed 90 MPH! But for most recreational riders, the out-of-the-box acceleration and 72 MPH top speed provides more than enough excitement.

Honda 400EX Key Features & Technology

In addition to the stout 397cc engine, the 400EX introduced many innovative features that improved performance:

  • Lightweight steel frame – Provided nimble handling and a flickable feel through corners and in the air. Kept wet weight under 400 pounds.
  • Progressive suspension – Offered 8.1 inches of plush wheel travel up front and 7.3 inches out back. 2001 brought adjustable IRS standard for greater control.
  • Dual carburetors – The engine used two Keihin CVK carburetors to optimize airflow and power delivery across the RPM range.
  • Racing styling – Aggressive ergonomics enhanced control while the styling looked fast standing still.
  • Safety – Mechanical front disc brakes provided strong stopping power while the steel rails and Nerf bars protected the rider.
  • Reliability – Honda’s legendary build quality resulted in a 500+ hour rebuild interval under normal recreational use.

The 400EX utilized cutting edge technology for a four-stroke ATV when it was introduced. It offered noticeably lighter weight than the 500cc two-strokes popular at the time along with smoother power and reduced maintenance.

Honda 400EX Handling, Ride Comfort & Customization

A huge part of the 400EX’s success was its confidence-inspiring handling. The race-bred chassis gave it very quick steering along with great high-speed stability.

The long-travel suspension easily soaked up rough terrain and big hits. But once Honda introduced independent rear suspension in 2001, handling stepped up to another level.

The IRS allowed the rear wheels to better follow the ground over uneven surfaces. This increased traction while reducing chassis pitch for a more controlled ride.

While the 400EX handled great in stock form, the aftermarket offered a wide range of handling and suspension upgrades:

  • Extended A-arms for greater wheel travel
  • Piggyback and coilover shocks for increased adjustability
  • +2″ swingarm kits to improve stability
  • Stem and bar kits for improved control and ergonomics
  • Triple clamps to sharpen steering response
  • Grippy paddle tires for improved turning and traction
  • Aluminum wheels and hubs to reduce unsprung weight

No matter your budget or riding style, you could dial in the 400EX’s handling to match via the plentiful aftermarket support. And the abundant plastic color options allowed you to easily customize the looks.

When it came to ride comfort, the 400EX was reasonably plush for a sport ATV. The long-travel suspension absorbed smaller bumps well and the seat was sufficiently padded. Taller riders did find the ergonomics a bit cramped though. Vibration from the single-cylinder engine was kept to a minimum as well.

Overall, the 400EX provided a thrilling ride that made you forget about comfort. The precise handling gave riders the confidence push their limits through corners or send bigger jumps.

Honda 400EX Reliability & Durability

Ask any owner and they’ll likely tell you the Honda 400EX engines are darn near bulletproof. The 397cc powerplant was overbuilt to handle intense recreational sport riding usage.

As long as you followed the factory maintenance schedule, changed the oil regularly and avoided excessive mud/water ingestion, you could expect 500-1,000 hours on a top-end rebuild. Some riders exceeded 1,000 hours on the original engine internals.

The transmission and drivetrain components were similarly robust. Issues like broken shifter forks were relatively uncommon compared to competitive models.

Of course, durability depends somewhat on how well the previous owner maintained the machine. Carefully inspect any pre-owned 400EX for signs of damage or abuse before purchase.

Provided it was properly maintained, a Honda 400EX will provide many years and riding hours of reliable high performance. Parts availability also remains excellent thanks to strong aftermarket support.

Honda 400EX Maintenance & Repair Costs

Maintenance costs on the 400EX were very reasonable for a high-performance ATV. It required oil and filter changes around every 20-30 hours of use, along with periodic valve adjustments as the shims wore down.

Regular air filter cleanings and fresh transmission fluid rounded out the basic maintenance items. With some mechanical skills, maintaining a 400EX cost about $428 annually.

When it did come time for a rebuild, costs were still affordable compared to modern sport ATVs. A typical 400EX top-end rebuild with new piston, rings, valves, etc could be done for well under $500 in parts. Bottom-end rebuilds rarely exceeded $300 for most riders.

The relative simplicity of the 400EX compared to more complex modern ATVs also made repairs less costly. And parts pricing remained reasonable given the huge production run.

So while not as maintenance-free as say a Honda Recon, the 400EX was still relatively inexpensive to own for a high-performance quad. The low cost helped offset the mediocre fuel efficiency.

Honda 400EX Ownership Pros

After reading through this review, it should be clear why the 400EX earned such a legendary reputation that endures today. Here are some of the notable ownership pros:

  • Potent high-revving 397cc engine provides incredible acceleration and top-end rush
  • Bulletproof reliability and easily rebuildable design
  • Lightweight, agile handling makes it a blast to ride hard
  • Plush long-travel suspension soaks up rough terrain and big jumps
  • IRS improves bump compliance and traction over previous years
  • Strong aftermarket support for maintenance, performance, and cosmetic upgrades
  • Very affordable cost of ownership compared to modern sport ATVs
  • Iconic styling and reputation make it a valued collector’s item

If you want an intensely fun sport ATV that won’t break the bank, the 400EX delivers excitement, rider-friendly handling, and reasonable running costs – a tough combination to beat.

Potential Cons To Consider

While the pros heavily outweigh the cons, there are some potential downsides of 400EX ownership to note:

  • Discontinued over a decade ago, so finding one in good shape is becoming difficult
  • Less stable at higher speeds compared to longer wheelbase models
  • Small 2.64 gallon fuel tank requires frequent fill-ups
  • Performance is eclipsed by modern fuel-injected models
  • Limited utility for towing or carrying cargo
  • Two-stroke models offer lighter weight and snappier throttle response
  • Lacks modern features like power steering or disc rear brakes
  • Won’t match the suspension sophistication or plushness of premium sport quads
  • Cramped ergonomics for taller or bigger riders

For many riders, the 400EX’s throwback charm outweighs any limitations compared to newer machines. But those wanting greater utility or long-distance comfort may want to look at other options.

What 400EX Owners Say?

To get the real scoop on ownership, you can’t beat insights from actual 400EX owners. Here’s what long-term owners highlight in their reviews:

  • “The best power, handling and reliability combination I’ve had in an ATV. Just couldn’t kill this thing no matter how hard I rode it.”
  • “Once I got the IRS model, this became the most fun quad I’ve ever owned. So nimble and easy to throw around despite the strong motor.”
  • “I bought my 400EX new back in 2000 and still have it today. Only needed minor repairs aside from regular maintenance. They just don’t build them like this anymore.”
  • “Awesome acceleration and loves to run wide open. But also forgiving enough for younger or less experienced riders.”
  • “The aftermarket support is amazing. I’ve built my 400EX up with tons of performance mods over the years as my skills improved.”
  • “I’m 6′ 3″ and do wish the ergonomics were a little roomier. But the tradeoff for that nimble handling is worth it.”
  • “I spent more keeping my YFZ450R running than I ever did on my bulletproof 400EX. The Honda just works, ride after ride.”

Owners universally praise the performance, reliability, easy handling, and reasonable running costs. The biggest complaints typically come from taller riders who find the ergonomics cramped.

Used 400EX Prices

As you’d expect for a highly regarded discontinued ATV, used Honda 400EX prices are holding up very well. Clean examples in good mechanical shape generally sell for $2,500 – $4,000.

Heavily modified or mint condition 400EX quads with very low miles can fetch over $5,000. The limited supply coupled with enthusiastic demand continues driving values up.

When buying used, prioritize condition over mileage or mods. Many have higher mileages thanks to the stout engines. Carefully inspect for signs of damage or abuse before purchase.

Considering their age, condition varies widely so patience can pay off if you hold out for a well maintained machine. A compression test is wise to assess engine health.

Non-running 400EXs can also be a good buy if you have mechanical skills. These reliable engines respond well to rebuilt carburetors, valves, top ends etc. Just factor in repair costs.

With Honda ceasing production long ago, clean low mileage examples will become even harder to find. Sooner is generally better if you hope to buy one before prices climb higher.

YearMake & ModelMSRPAverage Used Retail Price
1999Honda 400EX$5,599$3,800
2000Honda 400EX$5,799$3,500
2001Honda 400EX$6,199$4,100
2002Honda 400EX$6,299$3,900
2003Honda 400EX$6,499$4,200
2004Honda 400EX$6,599$4,500
2005Honda 400EX$6,799$4,800
2006Honda 400EX$6,999$5,100
2007Honda 400EX$7,199$5,300
2008Honda 400EX$7,399$5,600
2009Honda 400EX$7,599$6,000

The original MSRP increased steadily over the 400EX’s 11 year production run from 1999-2009. Used prices today range from $3,500 for early models up to $6,000 for 2009 examples in good condition. The discontinued status helps maintain strong residual values for clean low mileage 400EX quads.

Common Honda 400EX Problems and Solutions



  • Clogged radiator
  • Damaged water pump
  • Stuck thermostat
  • Lean fuel mixture


  • Clean the radiator
  • Replace water pump
  • Replace thermostat
  • Inspect carburetors

Difficult Starting


  • Weak battery
  • Fouled spark plug
  • Clogged air filter
  • Bad fuel pump
  • Carburetor issues


  • Charge/replace battery
  • Inspect spark plug and air filter
  • Test fuel pump and carburetors

Poor Performance


  • Clutch slippage
  • Clogged fuel filters
  • Air leaks
  • Valve adjustments needed


  • Replace clutch plates
  • Inspect fuel system
  • Check for air leaks
  • Adjust valve clearances

Oil Leaks


  • Worn seals
  • Loose drain bolt
  • Damaged gaskets
  • Cracked cases


  • Replace seals
  • Tighten drain bolt
  • Replace gaskets
  • Repair/replace cases

Noise & Vibration


  • Worn bearings
  • Damaged CV joints
  • Bent axles
  • Loose engine mounts


  • Replace bearings
  • Inspect CV joints and axles
  • Tighten/replace engine mounts

Electrical Issues



  • Replace spark plug
  • Test stator/CDI
  • Replace ignition coil
  • Tighten terminals

Carburetor Problems


  • Dirty jets
  • Stuck floats
  • Bad adjustment
  • Worn needle valve


  • Clean carburetors thoroughly
  • Ensure floats move freely
  • Adjust mixture
  • Replace needle valve

Regular maintenance and prompt attention to issues is key to minimizing problems and keeping a 400EX running strong. Most repairs are straightforward for DIY mechanics.

Top Alternatives to Consider

As great as it is, there are reasons you may want to consider alternatives to the Honda 400EX:

  • Yamaha YFZ450R – Fuel injected 450cc engine offers the most power. Fully adjustable suspension is more advanced as well. But maintenance costs are higher.
  • Suzuki QuadSport Z400 – Closest rival to the 400EX in a very similar package, though not quite as nimble handling. Fun value-oriented option.
  • Arctic Cat DVX400 – Race-bred sport ATV with a 399cc engine. Great choice if you prioritize low ownership cost.
  • Honda TRX450R – The 400EX’s successor in Honda’s lineup. Improves on it in most ways but at the cost of some reliability.
  • Polaris Outlaw 450 MX – Hard to match its acceleration and plush suspension, but more complex than the Honda.

While not perfect replicas, other used sport ATVs can fit the bill depending on your budget and needs. The options above provide improvements in areas like power, suspension and features but force tradeoffs as well.

Conclusion – Still a Legendary ATV Today

Decades after its debut, the Honda 400EX remains a highly capable and sought after sport ATV. Its strong high-revving engine, bulletproof reliability and accessible handling helped cement its legendary status.

While the performance gap has closed compared to modern machines, the 400EX still delivers an incredibly fun, confidence inspiring ride – especially at its reasonable price point used. Plus there’s great aftermarket support to customize these ATVs.

For anyone seeking a durable, easy to ride sport quad that prioritizes big grins per dollar over outright power, the 400EX remains incredibly appealing. Just be ready to potentially deal with its snug ergonomics for taller riders and hunt for a clean example.

The 400EX enjoys near universal praise from owners to this day as an amazing blend of power, agility, affordability and Honda reliability. So is this discontinued icon still worth buying used today? For most sport ATV applications, the answer is a resounding yes. The legendary 400EX has undoubtedly stood the test of time.

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