PROJECT MACHINE: 4-STROKE 250R

A TRX450R/CRF250R hybrid/quad takes on TT racing By the staff of Dirt Wheels

 

 

 

When we think of hybrid quads, those thoughts take us back to the late ‘90s and early 2000s when there was an odd transition going on in ATV racing. We’re talking about a time before quads like the LT-Z400, YFZ450, TRX450R, LTR450R, DS450 and KFX450R were released. The EPA was staking the heart of racing two-stroke engines. With Yamaha’s Doug Henry winning the 1998 outdoor national motocross championship aboard the Yamaha YZ400F, people began embracing the capabilities of four-stroke engines. That embrace extended to the ATV community.

Since few sport quads had been produced since 1989, the Pro ATV classes had a non-production bias. You could run aftermarket chassis, engines and different engine displacements in the same class. Pro riders started installing the new high-performance four-stroke dirt bike engines into customized ATV frames. Those builds led the way for the manufacturers to build the high-performance ATVs of today. The national pro series now has a production rule, but with Yamaha being the only manufacturer producing a 450 (the YFZ450R) and with the state of ATV racing as whole, we have a feeling that rule won’t last.

Daryl Rath, owner of Rath Racing, was one of those pro ATV riders who built some of the first hybrids. His newest creation is for his youngest son, Tucker Rath. It’s a doppelgänger of Daryl’s TT TRX450R, but with a fuel-injected CRF250R engine. This is one lucky kid!

 

 

LONG LIVE THE HYBRID

Rath wanted a replica of his TRX450R for his son, Tucker, but with a smaller powerplant, as Tucker is only 14 years old and can’t race the 450cc engine for a couple years. Starting with a TRX450R frame, the Rath Racing crew figured out how to make a 2015 Honda CRF250R engine fit in the TRX frame. They made their own billet-aluminum kick-starter that clears the frame perfectly for a full kick. Rath then made a custom intake, mounting a foam-wrapped K&N air filter. If the track is wet, the foam will soak up any mud or water.

The usual racing necessities were added, like Pro Peg mounts, custom Rath TT nerf bars, a front bumper and a rear grab bar. TT racing is all about a lowered center of gravity, so Rath Racing’s lowered OEM subframe modification is mated to a trimmed Fourwerx Carbon seat. They also added Rath’s new aluminum 1.5-gallon fuel tank, which holds plenty of fuel for 8–10-lap main events. The cylinder head went to Dasa Racing for porting and polishing to match a 14:1 CP piston. Rath modified a Dasa Racing exhaust to fit the CRF engine. The machine retained the OEM fuel injection from the CRF, so tuning the bike on the dyno is a breeze.

On the dyno it made 38 horsepower and 28 foot-pounds of torque to the rear wheels. The Rath boys prefer to use OEM brake pads and rotors on their machines, but Streamline Brakes provide the brake lines. The combination stops very well on the track.

 

With all of these great products, this 315-pound machine is a blast to ride. It’s on rails in thae corners, and the Dasa Racing-tuned engine keeps the torque flowing forward.

 

SUSPENSION, TIRES & LOOKS

Fox dual-rate, fully adjustable front shocks with Rath Racing TT A-arms, TT tie-rods and triple-bearing billet front hubs make up the front suspension. All of these products make for a very lightweight setup. Every TT racer should have Rath Racing’s front sway bar to decrease body roll in corners. It is fully adjustable for different track configurations. Tucker and Daryl both prefer a +1 stem with 1 1/8-inch anti-vibration handlebar clamps and a Fly Racing Aero CR High handlebar for TT racing. A Works Connection perch and lever assembly with a Motion Pro clutch cable make for smooth clutch action.

 

 

The rear end is trick. Beginning with a shorter RR chromoly swingarm, Rath added a lightened PRP bearing carrier, Lonestar Axcaliber adjustable axle, Lonestar billet rear hubs and a fully adjustable, dual-rate Fox Podium shock. This quad has only 7 inches of wheel travel at both ends! It is normal to have less wheel travel so the quad can handle better on hardpack dirt. There are usually just single jumps or “rollers” on TT tracks, so there is no need to add corner-hindering travel for small jumps. The Raths prefer Hoosier TT front and rear tires, which they groove differently for each track. The A5 wheels from DWT are a non-rolled-lip design to keep the weight down. The radiator shrouds are some of the coolest we’ve seen—FourWerx carbon fiber shrouds with air intakes on the side. Add the FourWerx carbon fiber front hood and you have a very light front plastic assembly. Rath prefers not to use front fenders. 75 Designs supplies the Rath team with killer-looking custom graphics.

 

 

THE RIDE

This 250cc machine is simple to start and fired on the first or second kick every time. The billet kick-starter  provided more than enough leverage and boot clearance to start this TT machine. While practicing starts, we could really feel how well this engine runs. Even though the quad is close to 100 pounds heavier than the complete dirt bike, it rips from the bottom of the rpm range all the way to the rev limiter (over 13,000 rpm!). The fuel injection allows zero bogging and crisp, instant throttle response no matter the gear choice. We were impressed and could not help but smile when we were on long straightaways listening to that shortened Dasa exhaust sing.

 

 

Even with a fast engine, this quad is one of the best-handling machines we have ridden with no front-end push in corners. We haven’t been in an F1 car, but we’re sure this is how it would corner! Rath Racing has really done its homework with the geometry of its front- and rear-end suspension components. This hybrid quad rails corners with perfection. There was minimal body roll thanks to the sway bar, which meant we could pitch it into a corner at a high rate of speed and it just kept tracking in the right direction. That was a huge confidence booster for us. The Fox shocks soaked up small chatter bumps on the track, yet could easily handle the rollers. Both ends felt a bit soft for us, but Tucker is around 130 pounds compared to our test rider at 200 pounds. We just dialed up the compression to make the shocks stiffer, and it felt better. The ergonomics of the quad were very comfortable. The RR Monster stainless steel pegs are longer than standard pegs and keep your feet planted very well. The Fly handlebar was a good fit for the quad and worked well for TT racing, and there was minimal vibration when coupled with the Rath’s anti-vibe steering stem.

The best part of this quad is how light it is. A stock TRX450R weighs 350 pounds without fuel or oil in it. Tucker’s quad, filled with oil and fuel and completely race-ready, weighs an outstanding 315 pounds! You can really feel how light it is when you are on the track. We felt less fatigue while riding this compared to another TT TRX450R we rode at the same time, and that has a lot to do with the weight of the machine. Rath might be adding some titanium goodies in the future that could possibly put the weight under the 300-pound mark!

 

 

FINAL THOUGHTS

Tucker Rath is a very lucky young man to have such an awesome quad! He has already been on the podium several times this season, and we can see that happening more often. Blood, sweat and tears were involved building this masterpiece, and it was our pleasure to be able to put it to the test. We give it an 11 out of 10 on the Dirt Wheels scale of approval. The question remains in our minds is, “Will hybrid quads make a comeback?” We think, “Why the heck not?” To add a quote from a great movie, “If you build it, they will come.”

PARTS AND SUPPLIERS

Rath Racing: www.rathracing.com, (320) 234-7223

RR TT nerf bars with monster peg (hybrid) $525.95

RR front bumper $124.95

RR frab bar $79.95

RR aluminum steering stem w/ anti-vibe 1 1/8” handlebar mount $424.95

RR billet steering stem clamp $39.95

RR TT A-arm kit (aluminum upper, chromoly lower) $994.95

RR TT tie-rod kit $224.95

RR aluminum 1.5-gallon fuel tank $649.95

RR triple bearing front hub kit $429.95

RR TRX frame service $475.95

RR TRX lowered sub-frame service $325.95

RR TT -1.25 chromoly swingarm $925

RR Sway bar $425.95

LoneStar Racing: www.lsracing.com, 480-834-2990

LS billet rear wheel hubs $236

LS Axcaliber adjustable width axle $449

Hinson Racing: www.hinsonracing.com, (909)946-2942

HR complete billet-proof conventional clutch kit $1,184.99

CP Pistons: www.cp-carrillo.com, (949) 567-9000

CP 14:1 piston kit $324.99

K&N Filters: www.knfilters.com, 800-858-3333

Air filter $70.39

Dasa Racing: www.dasaracing.com, 951-681-1131

Full exhaust $569.95

Port and polish service Price varies

VP Racing Fuel: www.vpracingfuels.com, (210) 635-7744

113-octane fuel $70 (5 gal.)

Rebel Gears: www.rebelgears.com, (931) 788-1617

13-tooth front sprocket $19.91

38-tooth rear sprocket $44.99

Hoosier Tire: www.hoosiertire.com, (574) 784-3152

18×5.5×10 TT front tire $100.95/tire

18.5x8x10 TT rear tire $107.95/tire

Douglas Wheel: www.dwtforum.com, (800) RACE-RIM

10X5 A5 front wheel $63.95/wheel

10×10 A5 rear wheel $86.95/wheel

FourWerx Carbon: www.fwcarbon.com, (262) 501-9696

X7 carbon fiber hood $184.95

Carbon fiber shrouds $399.95

Replacement seat foam $99.95

Wave seat cover $149.95

Streamline Brakes: www.streamlinebrakes.com, (909) 987-4214

Stainless steel braided front brake line $89.99

Stainless steel braided rear brake line $39.99

Works Connection: www.worksconnection.com, (530) 642-9488

Elite clutch perch and lever (CR style) $155.85

Fly Racing: www.wps-inc.com

Fly Aero CR high tapered 1 1/8” handlebar $66.95

WPS O-ring chain $21.95

75 Designs: www.75designs.com, (763) 439-1289

Custom graphics kit Price varies

Fox Shox: www.ridefox.com, (800) FOX-SHOX

Fox dual-rate front shocks TBA

Fox Podium 2.0 rear shock $1,094.99

Mystik Lubricants: www.mystiklubes.com

10W40 synthetic engine oil $6.28/qt

80WT transmission oil $6.28/qt

Fasst Company: www.fasstco.com, 877-306-1801

Rear brake clevis $39.99

Rear brake return spring $19.99