Are you man enough? By the staff of Dirt Wheels, Photos by Pat Carrigan 


It takes a talented rider to hammer a machine as powerful as a modified Suzuki LT-500R through a tight turn. You get impressive roost when it works.


We owe a great deal to dedicated ATV owners who spend the time and money to keep the legendary machines from our sport’s past alive and more than well. In this case, a Duncan Racing International, Inc. customer chose to unite two legends—Duncan Racing and a 1987 Suzuki LT-500R QuadRacer. The LT-500R moniker is all but lost in common vernacular; the machine has simply become known as “Quadzilla.” Quadzilla is an allusion to the fictional Japanese monster Godzilla that is, as you may imagine, not famous for its manners or vintage teapot collection. Godzilla is a giant, fire-breathing, city-eating monster, while Quadzilla is giant-pistoned, fire-breathing, dirt-eating monster. The nickname makes perfect sense.


Skat-Trak tires did a great job of getting the monster power to the sand, and that little rib on the front tires provided confident steering as well.


Duncan Racing had been in business for 10 years when the LT-500R arrived on the scene. Suzuki sold the 500 QuadRacer for four years, but Duncan Racing is celebrating its 40th year in the ATV Industry.

So, what drives a man to spend the time and money it takes to bring a 30-year-old sport quad to this level of perfection in looks and performance? Dedication and a love of powerful two-stroke ATVs. If you don’t already envy this guy enough, he has a Honda TRX250R that’s equally as nice and potent.


The chrome-plated +2 swingarm is no longer available new, but Duncan Racing claims they could have new ones fabricated for approximately $1000.


The mid to late 1980s was a dream time for two-stroke ATV enthusiasts, but both the Quadzilla and the legendary Honda TRX250R actually had four-year production lifespans. Honda TRX250Rs are still everywhere, but the Quadzilla is a far rarer bird.

After reacquainting ourselves with the LT-500R, we certainly understand why the Quadzilla is so rare. Everyone from top pros to teenage girls could easily ride a 250cc two-stroke sport quad. The same is not true when you double the size of the piston. Beginning with a 500cc two-stroke with no magic button to pulling in a clutch that will control major boost, a LT-500R is not a machine for every man. Once you do get it started, you face heavy vibration and must deal with the effects of a death grip on the handlebar to keep it from getting away from you.

While we are all warm and fuzzy over that fact that this machine exists in such a refined form after 30 years, this is a “daily driver” for a very special breed of quad rider.


Hitting jumps is easy with 500cc of boost. The rider didn’t even have to rev the engine much when he went looking for air time.



Duncan Racing started by getting the LT torn down to the frame before building the machine back up to be more potent and attractive than it ever was when new. Some parts were left stock, like the footpegs and front A-arms, but those parts and many others were chrome-plated at Pacific Plating or polished in-house. A stock handlebar (there is a reason that one of the most popular modern bar bends is QuadRacer) is used, and so is stock plastic. Duncan believes this may be the last full set of brand-new LT-500R plastic in existence, but that didn’t stop DR from trimming off the front fenders to give the machine a sleeker look.


The striking blue engine in the Quadzilla looked great new, but the cases soon grew scarred, but polishing the aluminum fixes that problem.



As you might expect with a 30-year-old two-stroke motor, the engine needed a complete rebuild, and it was modified at the same time. A rebuilt crank retains a stock rod, but the forged piston was modified, and the cylinder was ported as part of the Paul Turner Racing (PTR)/Duncan Racing (DR) engine kit. The full kit includes a PTR pipe, billet exhaust clamp for a leak-free pipe/silencer joint, Fat Boy 2 silencer, PTR/DR National porting, billet-aluminum Powerhead, Pyramid reed valve, pre-jetted Keihin 39mm PWK carburetor and a DR clamp-on K&N air-filter kit for stock airbox. Some parts of the blue engine paint that the LT-500Rs came with was freshened up, but here more parts were polished.


Elka’s Stage 4 shocks are thoroughly modern, but most of the other parts on this show-quality Quadzilla could have been on any LT-500R in the 1990s.


The sum total of the mods is a motor that fires pretty easily for a 500cc two-stroke. Throttle response is crisp and clean as well. The clutch pull is not modern, and the shifting requires a deliberate foot to avoid missed shifts. But, once the engine is fired, the Quadzilla is all about rapid, eye-watering, suck-you-off-the-seat acceleration. The Duncan-modded quad does not disappoint. It is blindingly fast with power that is smooth overall.


Despite the clean and highly modified look of the Duncan Racing Quadzilla, much of the front of the machine uses stocks parts that are plated, polished or powdercoated.


One area we would like to have seen addressed was that the 1987 LT-500R had a large gap between second and third gears. We imagine the parts are rare, but gears from the later-model gearbox would have been welcome with a tighter gap between second and third gears and third and fourth.


We found that the stock peg location seemed a little high, but otherwise, this monster quad is quite comfortable and easy to move around on. That is a good thing, since things happen fast with this much boost on tap. We drag-raced the Duncan Quadzilla against the Polaris Scrambler XP 1000, and the 1000cc machine didn’t get embarrassed but it did get left behind.

A 2-inch-longer swingarm with a Stage 5 Elka shock in the rear and Stage 4 Elka shocks in the front provide a nice ride in the dunes. The ride was surprisingly plush, but when the machine was jumped, it landed pretty flat and used every inch of travel.

The dunes are the best place for a machine like this Duncan Racing Quadzilla. You can use the power with ease, and it’s easy to keep the bike looking good. Why spend the money to build rolling art like this and then drag it into the dirt and rocks?

The only gripe we had with this LT-500R was the transmission. That isn’t a criticism of the machine build or its performance, but the gap between second and third was big. Vibration is an issue that we aren’t used to dealing with on modern machines, but it is a factor here. It isn’t terrible, but it’s a built-in feature of a 500cc two-stroke single.


Duncan Racing lavished a great deal of time and attention on the engine and suspension of this Quadzilla. The result is one sweet but potent machine.



We can’t imagine racing this machine against modern machines or using it as our everyday quad. The level of restoration and finish on this machine pretty much guarantee that neither of those fates will befall this machine. No doubt it will be treasured and used carefully and sparingly, but it just makes us smile to see such a perfect example of horsepower wars from decades back. For those who once owned one of these monsters, or the even larger number of enthusiasts who wanted one so badly at the time, owning a Quadzilla of this quality is a dream. We are happy that Duncan Racing made one owner’s dream come true.


DR/PTR National midrange engine kit $1799

Complete engine, trans, clutch rebuild, HP mods $695 + parts

PTR pipe, billet exhaust clamp and Fat Boy 2 silencer kit (included in National kit) $899

Porting by Loren Duncan $550

PTR billet Powerhead $250

Forged piston w/ DR mod $179

Pyramid reed valve $199

Crank rebuild by DR $150 + parts

DR flywheel mod $95

DR Keihin 39mm PWK w/ DR Super Flow carb mod $75

DR clamp-on K&N kit $129.95

VP C12 w/ Maxima 927 fuel Varies

DR C25 clutch $189

Hinson billet basket $259.95

RK 520 O-ring chain $89

SunStar 13/40 sprockets $24.95/$28.95

Maxima MTL Endurance gearbox lube N/A

DR chrome front bumper $199

Elka Stage 4 $1595

GPR steering stabilizer $525

Round-housing +2-inch swingarm $995

Durablue extended axle $489

Elka Stage 5 rear shock $1295

Skat-Trak Mohawks front 21×7-10 tires $129.95

Skat-Trak 8-paddle Edge rear 20×11-9 tires $199.95

DWT Red Label wheels $109.95 front, $149.95 rear

Durablue rear hubs $215 per hub

Crown Series F brake lines $119.9 rear, $39.95

Motion Pro cables Throttle, $19.95; clutch, $22.95

OEM yellow fenders Unobtainable DR Scott Wilson graphics kit $175

Pacific Plating chrome (must go through DR, no retail) $750

DR in-house Jimmy Brown polishing $600

Powdercoat frame $395