While the Honda TRX300EX is not directly linked to the birth of the race-winning TRX450R, it is partly responsible for the renaissance of the sport ATV segment. It is, after all, the forebearer of the highly-acclaimed Honda 400EX. But enough about pure-sport machines. In this guide, let us spotlight this small-displacement but ultra-reliable wonder.
The Honda TRX300EX (a.k.a. Honda 300EX, Sportrax) is a top-tier, sport-oriented machine released in the market from 1993 to 2012. Boasting a 282-cm3 4-stroke engine, 5-speed gearbox with reverse, and smart air intake positioning, the 4×4 has become the go-to quad for many off-roading enthusiasts.
1999, 2001, and 2007 saw major improvements to the 4×4’s gearing, suspension, and engine systems and are considered the best years of the Honda 300EX.
You may want to note these years if scouting for a pre-loved TRX300EX in the used-quad market. But personally, knowing when the machine received significant enhancements is not enough. That said, I urge you to read on and learn more about the offerings of this four-wheeler.
An Unassuming but Highly-Capable Quad
While not a certified Baja-winning four-wheeler, the Honda TRX300EX has long been recognized as a formidable competitor in these racing competitions.
The quad’s TRX450R-inspired bodywork could be among the reasons for receiving such reverence (although I find that amusing since the Honda 300EX entered the ATV landscape way ahead of the well-renowned racer). If you are wondering, (yes!) you read that right — the Honda TRX300EX debuted in 1993 and stayed in production until 2012.
Now to the machine’s fine qualities. The Honda TRX300EX boasts a powerful 282-cc SOHC engine that delivers impressive performance throughout the entire RPM range. Engine smoothness is greatly improved — thanks to its gear-driven counterbalancer reducing vibrations for a smoother ride. Furthermore, its automatic cam-chain tensioner eliminates the need for manual adjustments, ensuring hassle-free maintenance.
A CDI system with electronic advance guarantees reliable starts, while an electric starter makes it easy to get the engine up and running.
As for breathability, the quad’s snorkel-type air intake is cleverly positioned high in the frame, minimizing the risk of water and dirt contamination — thus ensuring uninterrupted performance.
The Honda TRX300EX’s carburetion and powertrain systems and throttle responsiveness are also pretty impressive, as you will later discover in the next section.
2003—2009 Honda 300EX Specs & Features
The TRX300EX has an air-cooled, single-cylinder, and transversely installed OHC power mill. The bore-stroke ratio is 74 x 65.5 mm (2.91 x 2.58 inches), while the compression ratio is 8.9:1.
A 32-mm piston-valve carburetor with an accelerator pump (later increased to 36 mm), mated to an oiled urethane foam air filter, handles the air-fuel mixture. Piston displacement is 281.7 cm³ (17.2 in³).
The engine is configured from the factory for low-altitude riding, meaning that changes to the carb settings are required for riding at altitudes above 5,000 feet (1,500 meters). Should you go this route, expect horsepower output to decrease by about 3.5% for every 1,000-foot (300-meter) increase in altitude. Otherwise, you should be able to enjoy decent performance figures with the quad’s stock settings:
|Honda 300EX Top Speed||55–60 mph (88.5–96.6 km/h)|
|Horsepower||21.2–25 hp (15.8–18.4 kW) @ 7,000 RPM|
|Maximum Torque||23.1–29.8 Nm (2.35–3.04 kgf-m, 17–22 lb-ft) @ 6,000 RPM|
|Fuel Economy||25–30 mpg (7.8–9.4 L/100 km, 10–12.7 kmpl)|
|Approximate Tank Range*||approximately 56–81 miles for a full fuel tank|
Fuel & Lubrication
The fuel tank capacity is 8.5 L (2.25 USgal, including 1.8 L/0.48 USgal reserve). Post-2009 models received an increased tank capacity of 10.2 L (2.7 USgal). Using lower Octane fuel is strongly advised against as it can cause engine knocking and eventual failure.
Lube-wise, the Honda 300EX uses a trochoidal oil pump and has a Forced pressure wet sump system. It has the following oil requirements:
- After draining: 1.5 L (1.6 US qt)
- After filter change: 1.6 L (1.7 US qt)
- After disassembly: 2 L (2.1 US qt)
Recommended engine oil is SAE 10W-30 of Pro-Honda GN4 4-stroke motor oil in the U.S. and Honda 4-stroke motor oil or its equivalent in other markets. Note that both OEM recommendations and alternative variants must have a minimum API grade of SJ and meet JASO T903 MA standards.
A five-speed constant-mesh manual transmission with reverse and a cable-actuated clutch system handled by a DID 520V/86LE or RK 520MOZ9/86LE O-ring chain delivers power to the wheels. This powertrain combo, coupled with an efficient and well-designed exhaust system and an aluminum cylinder head, makes the TRX 300EX extremely trail-friendly.
For your reference, here are the stock gear ratios of 2003–2009 Honda 300EX models:
|Primary Reduction Ratio||2.833 (24/68)|
|Transmission Gear Ratio – 1st||3.692 (13/48)|
|Transmission Gear Ratio – 2nd||2.529 (17/43)|
|Transmission Gear Ratio – 3rd||1.857 (21/39)|
|Transmission Gear Ratio – 4th||1.458 (24/35)|
|Transmission Gear Ratio – 5th||1.178 (28/33)|
|Reverse||5.415 (13/33 x 15/32)|
|Final Reduction Ratio*||2.923 (13/38)|
Ignition & Electricals
Ignition is a DC-CDI (Capacitor Discharge Ignition) system with electronic advance, with a timing of 17° BTDC at 1,400 ± 100 RPM (initial “F” mark).
A single-phase alternator serves as the quad’s charging system, while a 12V 8Ah/(10 HR) battery powers lighting and electronics. The recommended format is a maintenance-free YTX9-BS battery like a Caltric YTX9-BS AGM Battery (view on Amazon).
Tires & Brakes
Aluminum wheels — with a bolt pattern of 4/144 and 4/110 and an offset of 2+3 and 3+6 for the front and rear, respectively — are fitted with PV102 Ohtsu radials best known for their off-road performance and durability.
These tires measure AT22x7-10 (front) and AT22x10-9 (rear) and are replaceable with same-size ITP Holeshot XC Tires (view on Amazon) in case of wear or damage. They also require respective cold-tire pressures of 30 kPa (0.30 kgf/cm2, 4.4 psi) and 20 kPa (0.20 kgf/cm2, 2.9 psi), which can be adjusted by ± 3 kPa (0.03 kgf/cm2, 0.4 psi) depending on terrain conditions.
As for brakes, the quad has triple hydraulic discs — dual 174-mm front discs with Nissin single-piston floating calipers and a 220-mm rear disc, also with the same make of single-piston floating calipers.
Double wishbones with tube dampers and a trailing-type rear swingarm are in a double cradle steel frame (7° caster angle, 30 mm/1.2 inches trail).
The units have a wheel travel of 170 mm (6.7 inches) and 200 mm (7.9 inches). They also have dual hydraulic shocks (front) and a single shock (rear) with 5-way spring preload adjustability.
Other elements affecting the four-wheeler’s controllability over various terrains are a 1,145-mm (45.1-inch) wheelbase, a 117-mm (4.6-inch) ground clearance, and a 10.2-foot turning radius.
Dimensions & Capacities
The dimensions of the Honda 300EX are 1,720 x 1,105 x 1,063 mm (67.7 x 43.5 x 41.9 inches — L x W x H). Front and rear treads measure 857 mm (33.7 inches) and 850 mm (33.5 inches), while saddle height is 775 mm (30.6 inches) and is perfect for medium-height to taller riders. Conversely, the footpeg height is low-hung at 311 mm (12 inches) — much lower than the Honda TRX 450R.
Capacity-wise, the quad weighs 169 Kg (372.5 lbs.) dry and roughly 176 Kg (388 lbs., curb mass) across all markets and production models. On the other hand, GVWR is an estimated 304.5 Kg (671 lbs.) — inclusive of an 8.5 L full tank and fluids, curb mass, and a 120 kg/265 lb. maximum weight capacity.
This machine features a sporty and aggressive styling that reflects its performance-oriented nature. Honda 300EX plastics are sleek and sharp and designed to be durable while providing protection.
The quad has a streamlined and aerodynamic shape, with front fenders and rear body panels that enhance airflow and improve cooling. Instrumentation is straightforward and practical, with just the right gauges to inform the rider of speed, RPMs, and fuel levels.
Honda TRX 300EX Price
References for Honda TRX300EX MSRPs are a bit obscure since more online sources mistake this model for the same-class FourTrax that entered the ATV landscape within the same period. But based on data gathered by JD Power, the list price of 2001 to 2008 models ranged from $4,799 to $4,999, with low and average retail falling between $905 and $4,045.
As for auction listings, numerous sites post resale values between $2,500 and $2,999. There are some secondhand units sold for less than $1,000. But be wary when buying these, as they typically have a non-working battery, missing front fenders (view on Amazon), or a non-operational reverse gear and rear brakes.
Veer away from quads sold for less than $500, as they are almost automatically a (non-working) salvage item.
Honda Motor Company Ltd., a renowned automotive manufacturer, has a rich history going back to 1946. Founded by Soichiro Honda, the Japanese firm began its automotive journey with race cars, piston rings, and aircraft propeller automation.
Initially selling motorized bicycles and automotive parts, Honda expanded into various industries not long after and became one of the top contributors to the ATV segment — with race-inspired quads like the Honda TRX300EX.
Honda is globally recognized for its groundbreaking innovations in electric automobiles, energy solutions, and motorsport vehicles.
Conclusion — Honda TRX 300EX ATV Review
After a decade past its end of life, the Honda 300EX (or Sportrax TRX300EX) is gaining popularity due to its reliable and timeless mannerisms. It may not be a true-blue pure-sport like the larger-displacement TRX450R or 400EX. And yet, folks cannot deny its competencies off the road.
Unsurprisingly, this set of competencies made the 300EX a go-to machine for many off-roaders — and what continues to make it appealing for sport-oriented enthusiasts and even nouveau riders.
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.