BUILDING THE ULTIMATE OFF-ROADER: PROJECT HONDA TRX600
We make the Honda they should have built 22 years ago By the old-school editors of Dirt Wheels
Editor’s note: From time to time we will be sharing some articles from Dirt Wheels magazine issues of the past. This was one that was featured back in the February and March issues of 1998. Unfortunately, some of the products and companies mentioned in the article may no longer be around. However, the look back into ATV history is still important to share. Dirt Wheels made some predictions here about racing four-strokes, and while the Honda TRX400 wasn’t exactly like this project, it wasn’t that different. Suzuki followed with its 400, and the rest is history. Enjoy.
Building the ultimate off-roader, or at least our version of it, was our mission. This classic Dirt Wheels sport quad would be our first step in doing that. We got tired of waiting for an OEM to build it, so we set out to assemble everything off-road riders wanted in a smoking-hot recreational vehicle.
We patiently waited, anticipating that this will be the year that Honda releases a new sport ATV to pick up where the TRX250R left off some 10 long years ago. However, each year ,all we got was zip, nada, squat, nothing.
Since Honda’s product planners had not seen the light, we would show them our version of what the ultimate factory sport quad should be.
We wanted a versatile, powerful, easy-to-ride quad that had great suspension and handled like a dream. We based the machine on a proven design. We did not want to experiment with different frames and geometries.
WHAT YOU NEED
Mark Laeger, the man behind Laeger Racing (www.laegerracing
.com), has a reputation for building quality frames for Honda TRX 250R, 250X, 300 EX and Banshee owners. His frames have won more national championships than all the other aftermarket manufacturers combined, both on the GNC and GNCC circuits. Mark agreed to supply the frame, subframe, swingarm, front A-arms and shock linkage.
Laeger has one of the best suspension setups in the business. His Pro-Trax suspension kits allow racers to get up to 16 inches of wheel travel depending on the shocks used.
We wanted to keep our quad’s suspension travel lower and the center of gravity down. We opted for a stock 250R’s wheel travel of 9 inches up front.
Laeger supplied us with his +2-inch-over A-arms. On the rear suspension, Laeger uses a ’91 Honda CR500 motocross bike linkage. It allows from 10 to 12 inches of travel. That would be plenty for our project.
We wanted to use parts such as spindles, hubs, brakes, rotors and plastic components from a readily available quad like the 300EX. Laeger makes a frame that allows you to use the stock plastic and component parts off either a Honda 250X or the 300 EX. We already had an EX, so all we needed was a motor.
The idea of a monster-displacement, low-pollution four-stroke intrigued us. Honda’s XR600 dirt bike engine fit the bill. This 591cc four-stroke had lots of torque and good reliability. The four-valve, SOHC, air-cooled engine weighs in at 100 pounds. While not exactly a lightweight, it was not out of the ballpark, either.
American Honda’s Bruce Ogilvie supplied us with a used motor. Laeger assured us he could make the XR600 fit his 250X/300EX chassis.
PUTTING IT ALL TOGETHER
We had to merge the parts from a Honda 300EX with the engine from an XR600 dirt bike and a Laeger’s EX chassis. We were looking at $2300 for the Laeger frame and subframe, as well as an extra $525 for Laeger’s +2-inch A-arms, ball joints, bushings, bolts and tie-rod ends. The ’91 CR500 shock linkage sells for around $400 at your local Honda dealer.
If you already have a 300EX, you can save quite a bit of money by bolting on the gas tank, plastic, wheels, axles, brakes, bumper, grab bars, airbox, spindles and miscellaneous parts. For the engine, make sure you get the carb, coil and spark-plug lead you will need.
We also used an XR600R right-side footpeg so the kickstarter would not interfere with the peg and the installation of the XR600 motor mount nuts and bolts in the Laeger frame. We also mounted an XR600 rear brake pedal because we liked the feel and the fit.
PAINT, DRIVETRAIN & WHEELS…
Maier Plastic (www.maier-mfg.com) supplied white 300EX plastic that bolted right on. We ran an RPM adjustable axle and dual-row axle carrier. Holeshot tires (18×11-8 rear, 20×11-10 front) mounted on Douglas beadlock aluminum rims handled traction.
Our project machine ran stock EX brake rotors and calipers with Graydon steel-braided brake lines. On the 300EX airbox, we found that a ’96 air boot fit our machine better than the ’97 model. We also used a stock EX seat, but plan on updating this in the near future. Our quad used Laeger’s flip mount for the rear plastic to clear the kickstarter.
SPECIALTY ITEMS & ASSEMBLY TIME
The XR engine requires the fabrication of a 2-quart oil tank. Gary Jones made us a custom aluminum oil tank that resides just in front of the engine and hooked up the XR’s oil lines. He also produced a custom WB head pipe and SuperTrapp exhaust.
It took three people the better part of four hours to get a complete rolling chassis. The EX parts bolted right on the Laeger chassis. It took several attempts before we managed to contort the XR600R engine at just the right angle and lodge it in place.
Once we had the engine in the frame, the rest was easy. Everything else just bolts on. We were bleeding brakes and checking all the nuts and bolts. We set a ballpark adjustment on the camber and toe-in on the front end.
It was time to fine-tune the package, set up the suspension and get the engine running properly. Finally, we will get all the details finished up. Without tuning, the project earned good reviews.
“Honda should have made this years ago,” said reigning Grand National champ Shane Hitt after his project TRX600 sport quad ride on DW’s exclusive torture track—a track that few race quads would feel comfortable on, much less a mild-mannered sport machine.
“We would all be racing four-strokes if they had,” chimed in newly crowned Pro/Am four-stroke champ Jeremy Schell. “I’d love to race something like this in the Open class. On the right track, it would be competitive against the Banshees and the big-bore-kitted 250Rs out there now. Imagine how fast it would be if the motor was hopped-up?”
“I’d race it against 250Rs; it’s got so much torque,” added 250 pro racer Kory Ellis. “The suspension is good, the brakes are great, and it is one of the most predictable quads I’ve ever ridden. Are you sure Honda isn’t releasing one this year?”
Honda will not be releasing the mighty TRX600 this year, or any other year that we know of.
THEIR LOSS, OUR GAIN
This was a hybrid vehicle that we had put together using miscellaneous parts and products combined with an aftermarket ATV chassis and various components from other ATV companies. We came up with our own version of what a ’98 TRX600 might look like if the factory had chosen to make one.
IT AIN’T BRAGGING IF YOU CAN DO IT
As actor Walter Brennen was so fond of saying, “It ain’t braggin’ if you can do it.” Once we had assembled the frame, engine, tires and miscellaneous pieces into a working vehicle, we were left with the fun part—testing it.
The idea behind our project was that anyone with the resources could make this vehicle. All you would need is an XR600 engine out of a dirt bike, a 250X or 300EX for miscellaneous parts, and lots of spare cash to purchase a Laeger chassis, swingarm, front end and WP suspension package.
HOW PRACTICAL IS THIS?
The amount of time, effort and expense involved in a project such as this makes it unique. We were able to build our prototype in a matter of days. Someone else would need to spend considerably more time and money than we did to make something similar. A ballpark figure for the cost of this project would be in the $6000–$7000 price range, assuming you already had a 250X or 300EX to start with.
Figure anywhere from $500–$1000 for a good used XR600 engine and transmission. The ’91 Honda CR linkage you need for the Laeger chassis will set you back another $400 at your friendly local Honda dealer.
We installed WP shocks from White Bros. to handle the suspension duties on our project TRX600. The dual front shocks retail for $760 for the set, while the single rear shock sells for $645. The prices climb even steeper once you factor in specialty items such as the handmade exhaust, custom oil tank and one-off skid plates. The price is reasonable for the performance.
HOW IT ALL WORKS
After we had put the rolling chassis together, White Bros.’ chief R&D specialist, Gary Jones, lent his expertise to the project. Gary installed WP suspension on our quad and hand-crafted the custom oil tank and skid plate. Gary also spent long hours detailing and ironing out the myriad details involved in a project such as this. Gary also tagged along on our first riding outing to see how his efforts would pay off.
“It started right up the first time I kicked it,“ exclaimed Gary, “but it sputtered and popped on the top end, so I knew the jetting was too lean. Because we were using the 300EX airbox, and the XR600 engine needs a lot more air, I knew we had to richen the mixture up.
“I richened the jetting on the stock XR600 main jet and put a K&N gauze filter with a PC-1 pre-filter over it. We then installed a trick, see-through, vented Moto Force [(541) 923-5467] airbox lid [$29.95] for the EX airbox. It helped the engine run much better. These things are really trick. You can see inside and tell if the filter needs servicing without removing the top.”
The next step was an exhaust system. Gary took one of White Bros.’ Eclipse-series mufflers and adapted it to fit with the stock XR600 head pipes. “We ran 10 discs in the unit, but you can run anywhere from 8 to 15. You add more discs for horsepower and less to make it quieter,” says Jones.
“The compression- and rebound-adjustable WP shocks are made in Holland and marketed through White Bros. They are a good all-around shock that can be rebuilt and dialed in to suit a wide variety of conditions. They gave us a good 10 inches of wheel travel and overall tuneability.
“In the back, a WP single rear shock with dual-rate spring, and adjustable compression, rebound and preload settings gave our TRX 10 inches of wheel travel out back. We could have gone for even more travel with longer shocks, but we ran standard 250R-length shocks to keep the center of gravity as low as possible on the TXR600.”
“Our computer graphics man at White Bros., Peter Kozlowski, came up with a trick-looking TRX600 logo for our quad. We plastered it on both sides of the Maier plastic. We covered it with a clear acetate background, then added a clear number-plate background over that. We had a production-looking machine.”
Gary Jones, Kory Ellis, Jeremy Schell, Shane Hitt and the usual gang of Dirt Wheels testers each got their chance to put the TRX through its paces. Every one of them had a positive first impression. They talked about how easy it was to ride and how comfortable, torquey and fun it was.
The mighty XR600 engine, even in stock trim, pumps out very controllable and broad torque. It made riding the beast almost effortless. You could leave it several gears high and let the torque pull you out of the corner faster than you thought possible.
“It was hard to tell that you were on a four-stroke,” remarked 250 Pro Kory Ellis after his test session. “The XR600 engine hooks up in a big way. It is much smoother and faster than a standard 250R, but not tippy like a 300EX in the turns. The Laeger chassis allows it to handle like a 250R when jumping, sliding and going through the whoops.
“This thing would be great on a flat or TT track. If Honda made one, I’d buy it and race it,” said Kory.
After Jones took the machine out, his ear-to-ear grin revealed what he felt about the 600. “This thing is awesome,” he remarked. “The chassis is outrageous. It is very predictable and easy to ride. You can slide it, rail it or do whatever you want with it in a corner. It is very confidence-inspiring. I couldn’t feel it flex anywhere. You don’t feel any vibration through the frame from the motor. I’m impressed. Laeger has done his homework with this chassis. The brakes work really well, too. I think the rear works even better than a stock EX because we’re running the longer XR600 brake pedal. That gives you more leverage. It’s neat. No oil leaks, either. I’m glad to see my work held up.”
STUFF TO FIX
Our first few rides revealed that we can improve in a couple of areas. We will be lengthening and widening the right-side footpeg (borrowed from an XR600 dirt bike) to make a more secure perch for the rider’s right foot.
We also plan on going a bit stiffer on the shock damping on the front and back to make it work better off big jumps and softer on the low-speed damping to make it plusher in the slow-speed braking bumps.
Gearing might be a bit on the high side. Depending on what type of event we will be racing it in, we might try lowering the overall gearing a bit. With the gearing and tires we are running now, we figure it will probably top out at around 70 to 80 mph.
An average horsepower reading for a stock XR600 engine is around 35. We are pretty sure we can get close to double that amount with a few modifications. Gary Jones tells us he can extract close to 60 horses from a modified XR600.
We plan to add a thicker padded seat in the future for a cushier long-distance ride. We will try some different tire-and-wheel combinations. This to see what type of tire and size might be more appropriate for the various events we plan on attending. The first thing Gary Jones told us after his test session was, “Hey, when are we going to a Grand Prix so we can kick some booty with this thing?” Gary, it’s only a matter of time.