Four-wheel fun you can afford

Budget build by the staff of Dirt Wheels

This build rides quite well for a reworked 2002 Honda TRX400EX. It is much more plush than stock.


In world history, the Dark Ages were well before the discovery of America, but for the sport ATV world, the dark ages were the 1990s. Yamaha kept the sport quad light burning with the Blaster and the Banshee, but other brands shied away.

Just 10 years earlier all four brands had performance two-stroke ATVs and had fun riding, racing, and going crazy. Then, in 1998, 10 years after the last Honda TRX250R, the 1999 TRX400EX was released. It revitalized the sport quad landscape. It didn’t make a stellar motocross racer, but it was great in the desert and is a great trail and play quad that stayed in Honda’s line for 16 years. This particular unit is a 2002. The owner is a long-time off-road fan and fabricator. He performed the modifications with care and maintained the machine well.

We asked to test it, but it had been sitting for a while. The carburetor needed work, and the ignition key had gone missing. We contacted Power Sports Nation  http://www.powersports   the nation’s largest supplier of used parts for quads and UTVs. We ordered a carburetor and an ignition switch with a key. The correct parts arrived quickly, and they were in nice condition.

We also purchased a fresh battery. We were in business after we cleaned and installed the carb and the other parts. The Honda ran like brand new, and it is like a time capsule of the early 2000s. It even had current off-road registration!

A full FMF exhaust was bolted to the 400EX. Most of this build was built a long time ago but was very well taken care of.



All TRX400s employed a modified, e-start version of the popular Honda XR400R motorcycle engine. In its first year, Honda teamed with Dirt Wheels to win the Baja 1000 on a near-stock machine, but older two-strokes continued to dominate motocross and GNCC racing. For 2005 the EX got suspension upgrades, reverse gear, and new bodywork. Another facelift followed in 2008, and in 2009 it became the TRX400X. The final year was 2016, making it one of the longest-running sport quads on the market.

We get to ride a lot of brand-new machines, and you would think that we wouldn’t get excited about a 15-year old quad with no reverse. In this case, the design and look of this machine evoke memories of an exciting time in sport quad history.

We also approve of the design goals of the owner. He had some specific ideas about what he wanted his quad to do. Nothing on this machine is superfluous. And then there are the lights. They just look cool. The owner actually had an LED light bar on the machine, but he likes the old-school look of the three Hella 1000 lights that are converted to HID. The lights take a little time to warm up, but they are vastly superior to the stock light.



The aftermarket responded quickly to the TRX400, and the owner of this machine began to personalize it. Nerf bars aren’t necessarily a must-have purchase for trail and dune riders. In this case, IMS/Roll Design pegs were added, and they provide secure footing without hanging up on rocks easily. The Roll/IMS collaboration has ended, but you can still get the pegs from Roll. This TRX has a Roll Design brake pedal, but it is no longer available.

A stock Honda TRX400EX runs pretty well, but the owner wanted more. A stainless steel FMF PowerBomb header was chosen for toughness and performance. Behind the header is a stainless and aluminum FMF exhaust with a spark arrestor. Both have performed well for many years. The other engine mod was a swap to a Uni Filter air filter element. The owner drilled out parts of the airbox for more flow.

After the engine was breathing more freely, it was time for upgrades in the handling department. Keeping in mind that this quad was for fun, the owner kept the mods mild. A comfy Ceet tall desert seat and a Renthal Fat Bar in RoxSpeed mounts open up the riding position. At one end of the bar is a Motion Pro twist throttle and cable. One of the coolest additions is a fabricated Se7en Racing aluminum oil tank that has three cooling channels through the middle. We couldn’t find that it is still available. The other oil system mod was Scott’s Performance reusable stainless steel mesh oil filter.

While on the subject of fluids, an IMS 4.3-gallon desert tank holds ample fuel. Over the years this TRX had a natural translucent one and now a black one. The gearing was dialed in for the various riding areas with Sunstar countershaft sprockets ranging between 13 and 15 teeth depending on conditions. It runs a D.I.D O-ring chain. Protection is in the form of a front bumper and under-frame skid plate of unknown origin. 

A set of Hella Optic lights with HID bulbs light the path at night. A custom aluminum rack was made up to hold them.



When his friends started riding 450s, the owner had no problem keeping the pace, but it was time for suspension mods. With the 450s dominating racing, there were used bargains to be had on eBay for the TRX400. He snapped up a new Dura Blue Eliminator 2+2 axle for $200! He scoured eBay and came up with Houser long-travel +3 A-arms for $240.

Fresh silver powder coating and new bearings were an additional $250. The arms are no longer made, but Houser has +2 stock travel arms. An Elka rear linkage sporting 10.9-inch travel costs $60, but they are no longer made for the TRX400. The fully adjustable Elka front shocks were $600, and a Stage 3 Elka rear shock emptied the wallet another $425. Those used prices are approximately the same as the Elka Legacy kit sold now.

Those parts required extended front braided brake lines and extended 4130 tie-rods. A stock Honda TRX400EX is a sporty ATV that handles well. However, the stocker can’t touch this widened machine with added wheel travel and quality, adjustable Elka shocks.

Finally, after the stock tires wore out, We mounted a set of GBC Motorsports XC Master front tires in 21×7-10 and rear 20×11-9 Ground Buster IIIs. The tires were installed on a used set of GMZ bead lock wheels. Since this machine sees a lot of sand dune action, a second set of used rims was located, and they had paddle tires mounted. That makes swapping from trails to dunes easy and quick.

IMS/Roll Design created the footpegs, designed with a kick up, and rear brake pedal as well.



The suspension modifications are the first, the very noticeable difference you feel on this budget trail and dune mount. The machine feels wide and stable with the axle and A-arm setup. Naturally, the Elka shocks were a massive improvement in suspension action and ride quality as well. Shock setup is a highly personal science. The machine is set up for a large rider, so it worked amazing for our heavier guys, but it was hardly surprising that it did not work as well for lighter riders.

The upright riding position and tall, comfortable seat make standing up from a seated position easy, and the riding position is open and comfortable once the rider is up on the pegs. We worried about riding rough trails without heel guards or nerf bars, but the IMS/Roll pegs never gave us a hint of a problem.

Our staff spends a lot of time on race 450cc quads and 1000cc sport 4×4 quads. We had to keep reminding ourselves that the 400 is a trail machine, and for trails, it has plenty of power. The owner claims he has no trouble riding with groups of 450cc machines in the dunes. We’ll chalk that up to rider skill.



The Honda TRX400EX is an easy sport ATV to modify and maintain. Riders enjoy the air-cooled simplicity of the TRX. NADA and the Kelly Blue Book value of a TRX of this era is around $1000, but when we looked at actual machines for sale, ordinary ones were roughly twice that, and some exceptionally nice ones commanded $4000 to $5000.

The key point is that a stock or modified TRX400EX is far less expensive than a stock 450 or a 450 modified of the same level. And, in general, the engine has much longer service intervals than a 450. This machine runs perfectly after 20 years of hard riding. This is a fun machine that will hold its value but won’t break the bank.

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We tossed on a fresh set of GBC XC Master front tires and Ground Buster III rear tires to rip through some tight trails on this Honda.



Ceet Racing: (760) 599-0115,

Tall desert seat foam $89

Seat cover $49

D.I.D. Racing Chain:

O-ring chain: VO, $37.51; VX2 black, 

$111.31; VX2 gold, $123.66

Dura Blue, Inc.: (949) 770-5533,

Eliminator 2+2 axle $200 eBay

Elka Suspension: (800) 557-0552,

Rear linkage (10.9” travel) $60 eBay (no longer available)

Front shocks $600 eBay

Stage 3 rear shock $425 eBay (now Stage 4 $1009.99)

Stiffer shock spring $85

FMF Racing: (310) 631-4363,

PowerBomb $324.99

PowerCore 4 $399.99

Hella 1000 converted with HID eBay

GBC Motorsports:

XC Master front tire $73.42

Ground Buster III rear tire $91.06 ea.

Houser Racing: (740) 382-8100,

Long-travel +3: (eBay) $240 + powdercoat 

and new bearings $250 (only +2 standard travel available now)

Brake lines $90

IMS Products: (800) 237-9906,

4.3-gallon desert tank $347.50

LoneStar Racing: (800) 4LSRACE,

Parking brake block off plate $16.80

Motion Pro: (650) 594-9600,

Twist throttle kit $42.85


Fat bar $91.95

Roll Design: (760) 731-5920,

Footpegs $274.99

Brake pedal: Discontinued

Scotts Performance Products: (818) 248-674,

Steering damper mount kit for the TRX SS mesh oil filter $69.95

Se7en Racing:

Oil tank Not available

Sunstar Sprockets: (937) 704-1462,

Countershaft sprockets (13–15 tooth) $23.95

Uni Filter: (714) 535-6933,

Filter $34.95



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