Published on December 12th, 2012 | by Joe0
Kawasaki KFX450R Motocross Build
Plugged in, uncorked, and smoothed out, we tap into the KFX450R’s hidden track potential.
Kawasaki’s KFX450R continues to walk a fine line between rider-friendly sport quad and race machine. Its power delivery, reverse gear, and 46.1 inch width make it ideal for the trail; while its rigid aluminum chassis, razor sharp handling, and phenomenal brakes remind you that this machine was built for competition. With just a few add-ons, we turned our Kawasaki KFX450R into an even better trail machine or budget cross-country racer. With a motocross build in the works, we were optimistic about the machine’s track potential; however, with fewer numbers of Kawasakis at the tracks we frequent, we wondered if we were building on a mistakenly overlooked ATV or if there was something we just didn’t know. Kawasaki’s factory team won some nationals, but their budgets are limitless compared to most privateers, or local racers. After hours of testing, phone calls, and consideration, here is the setup we employed to make the KFX450R ready for the track and an impression of the results you can expect from your machine.
Dave Trimble and Chase Cunningham have raced for years and each participated in ATV on Demand’s 2010 450cc Motocross Shootout making them ideal candidates to test our project KFX. Dave was also kind enough to assemble the project for us. For our testing, we visited Nickota MX in Bedford KY, and Bar2Bar MX located in Mt. Sterling, KY, the home of our 2010 shootout.
Dumping a ton of money into your motor is unnecessary for most racers. Too much power will actually make you slower and shorten your engine’s life unnecessarily. Adding an aftermarket exhaust, removing the air box lid and rejetting, or adding an aftermarket fuel management system is all that is required to tap into the full performance potential of stock engines. The Kawasaki, however, requires the use of a different intake. There’s an abrupt 90-degree bend in the stock intake tract that disrupts airflow, stifling horsepower production. In comparison, Fuel Customs intake has only a mild curve and is almost as big around as a coke can at the smallest point. Fuel Customs intakes are available with or without their lidless air box, which offers some protection from beneath. The intake kits come with Fuel Customs 8-ply cotton filter and pre-filter, which they swear by. We still wish they offered a foam filter option for dusty conditions.
On our trail build, we utilized an HMF Competition slip-on exhaust system and Fuel Optimizer. We liked the ease with which we could quiet down the exhaust or open it up for more power, plus we loved its black and polished silver appearance. If you are running the stock intake, the slip-on model is sufficient; however, HMF felt that running a full competition system would allow us to make the most available power with the Fuel Customs intake and HMF Optimizer.
HMF’s Optimizer allows for on board programming without the use of a laptop. Choosing between 8 numbers at half point increments, there are 16 total levels of fuel that you can add or take away, at three different RPM levels: idle to ¼ throttle, ¼ to ¾ throttle, and ¾ to full throttle. The Optimizer comes pre-programmed for an exhaust with the air box lid removed. We pumped the idle to ¼ setting from 1.5 to 3.5 when we tested the slip-on Competition Exhaust, as the base setting was too lean. When we added the Fuel Customs intake and Full Competition exhaust, the engine barely wanted to run with our original settings as the huge addition of air flowing in was letting the engine starving for fuel. We pumped the Optimizers’ settings up to 6, 7,7 and things have been running smoothly since.
The Kawasaki’s frame is tough, rigid, and responsive, providing a good platform around which to develop a race machine. With a 50 in. width rule enforced in most major series, the KFX has room to grow and stability to be had. We chose Teixeira Tech’s Maximum Ground Clearance a-arms to widen the front of our machine for a few very specific reasons. Ed Teixeira is an experienced motocross and desert racer, so he understands the importance of keeping parts light, but doesn’t sacrifice on durability. The tig-welded arms are constructed of 4130 chromoly. They make the KFX +2.125in wider per side and move the front wheels forward ½ in. Moving the front wheels forward extends the wheelbase for better high speed stability; it transfers weight to the rear tires for improved traction, and reduces the rear end’s leverage over the front end, helping keep the front end down on acceleration and jumps. The new arms allow for the use of long travel shocks and more suspension travel–– two things the KFX really needs.
Teixeira’s biggest advantage over the competition is their easy-to-use Caster adjustment system. Being able to add or remove caster, or move the top ball joint rearward or forward, allows you to add high-speed stability or speed-up steering. Most other systems require you to carefully and correctly measure the front end on a flat surface in order to prevent misalignment, which is why many amateur racers rarely mess with it, and often wind up with front ends that aren’t dialed in properly. Teixeira’s five-position adjustable notched upper a-arm and castle washer system let you choose in between 3 and 8 degrees of caster. Caster changes take less than three minutes, and the process is virtually fool proof, with no need to measure. This gives you an edge over your competition by allowing you to easily and quickly dial in your steering for faster or tighter tracks.
Teixeira Tech uses Italian-made, sealed Frap ball joints, which they say are the finest available. We upgraded the standard Delrin bushings with needle bearings to reduce maintenance, and to save money on replacement part costs over time. Standard Zerk fittings come standard, allowing you to easily grease front-end pivot points. Wrinkle Black powder coat is the standard finish, but Teixeira offers a number of custom color and chroming options, which we took advantage of.
To widen the back of our KFX, we utilized a Lone Star Racing, Axcaliber Pro Racing Axle. The pro model received a new profile for increased strength and a new, hard chrome finish, which has a stainless steel-like appearance. The axle allows you to widen the machine between 1.5 and 4.5 in., using three ½ in. spacers on each side. The Axle has a true unlimited replacement warranty against bending or breaking, which can be transferred to another person, should you sell your axle, or machine, in the future. The stock swingarm is strong and 5 to 7 pounds lighter than most aftermarket swingarms. Its length is close enough to ideal that we felt it was worth leaving alone.
While overspending on your engine can be a mistake, it’s hard to overspend when it comes to suspension. Race Tech’s suspension components are some of the highest quality in the industry. Our Race Tech GS-3 shocks feature 46mm zinc-plated, steel bodies and chromed 5/8 in. steel shafts. Most of the remaining components are constructed of aircraft-grade aluminum while the eyelets feature stainless steel, spherical heim joints.
The internals are comprised of Race Tech’s famous Gold Valve, which was developed to prevent oil flow restriction at the piston, helping prevent high-speed harshness. Custom valuing and spring rates are selected based on your rider weight, type of riding, ability level, and, of course, specific chassis setup. Chassis setup also determines the shock’s length. For our Teixeira arms, Race Tech built us 18 ¾in. long front shocks and a stock length 17 in. rear shocks. The Zero Preload Race Series GS-3 shocks feature high and low speed compression and rebound adjustment.
A steering stabilizer acts as suspension for your steering. We carried Precision Racing’s Pro model steering stabilizer over from our cross-country build, where it really helped us get a handle on the stock KFX’s twitchy front end. The precision steering stabilizer was the first that allowed you to tune the bump absorption quality of the center and sides of your ATV’s steering individually. Their new Pro model benefits from a built-in reservoir to compensate for thermal expansion, reducing fade during long, hot races.
The addition of longer a-arms requires the use of longer brake lines. Streamline stocks brake lines in various colors for most applications, or they can build whatever length lines you need. We installed a set of blue+3 in. dual lines up front with a standard length line out back. The steel-braided lines improve your brakes’ power and feel, especially once your fluid starts heating up late in a moto. Our front brake lines were secured to the upper a-arms with Streamline’s clean-looking, billet brake line clamps, which are also available in various colors.
Fasst Company’s Brake Return Spring kit allows you to adjust your rear brake pedal’s resistance, while eliminating the stock return spring. The kit is also claimed to minimize the amount of debris reaching your master cylinder. The clevis at the bottom of your brake’s return spring is an area that develops play over time. Fasst Company’s brake clevis eliminates this unwanted play; both it and the return spring bucket are made of billet aluminum and are available in a number of anodized colors.
Wheels and Tires
We wanted a set of wheels that would last for the life of our KFX both structurally and cosmetically. Hiper suggested we run their Tech-3 single beadlock wheels at both ends. The Tech-3s feature a billet center, sandwiched between two carbon fiber halves, sealed together with rubber o-rings. Our test riders have attested to the strength of these wheels based on personal experience. Should you damage one, they are completely modular. Whichever part of the wheel was damaged can be replaced individually with no special tools or the expense of replacing an entire wheel. Also, unlike powder-coated aluminum wheels, the color of the Hiper wheels, or their various colored beadlock rings, will never scratch or chip away.
8×8 in., 3+5 offset wheels were installed out back and 10×5 in. wheels with a 4+1 offset went on up front, replacing the stock front wheels’ 3+5 offset to improve handling by reducing bump feedback and reducing steering effort.
A small trade-off for the Hiper wheels’ toughness is that they do weigh a bit more than some of the lightest aluminum race rims currently available. To keep power loss through rotting mass down, we wanted to make sure we ran the lightest tires possible. ITP’s Quad Cross MX Pro Lite tires are designed to work best on hard-packed track surfaces, which are common in ATV racing. Compared to the standard Quad Cross MX tires, the Pro model Quad crosses feature a softer rubber compound for better hookup. Their two-ply design makes the front tires 1 pound lighter each, while the rears are 2 pounds lighter per tire. These tires alone saved us 6 pounds in rotating mass, and have proven themselves capable of winning Pro Nationals in the past with Team Kawasaki.
Another product we carried over from our cross-country build was Precision Racing’s Shock and vibe bar clamp. They help reduce the vibration transferred to the handlebars by the Kawaski’s aluminum chassis and help reduce impacts felt through the handlebars. They also raise the handlebars around 1 in. creating a more comfortable cockpit.
Spider Grips’ Slim Line SLX grips are also designed to dampen vibration with their dual layer design. The surface’s compound is designed to be tacky to the touch, keeping you in better contact with the machine with less effort. They are a bit slimmer than Spider’s A-3 model, in case you prefer a grip with a smaller diameter.
To protect ourselves from other riders and our machine, we installed a set of Bling Star’s Notorious nerf bars and heel guards. The Notorious nerfs are very light and feature closely-spaced nets that wrap around the frame for increased safety. The innovative Notorious heel guards feature a two-piece design with an elastomer between the two pieces. This helps prevent the cracking common on many aftermarket aluminum heel guards by allowing some flex. The netted heel guards come with an aluminum heel plate and provide plenty of room.
While the KFX’s chassis is tough, we don’t like the idea of the bottom being beaten on. The genuine Kawasaki chassis skid plate is one of the few on the market that covers the entire underside of the frame from front to back. We also added a genuine Kawasaki swing arm skid plate to the build, specifically for use on tracks where rocks often pop up. Both items feature thick aluminum and fit precisely.
Graphics and Numbers
G4, formerly Go For it Graphics, has been producing graphics since 1999. They offer a ton of styles that can be totally customized with lots of color combinations, plus they can add sponsor logos to your graphics. G4 also offers number plate backgrounds in various styles with custom colors, rider name, or logo options.
We ordered their newly released, Phoenix style graphics and number plate backgrounds in a wild looking green, black, and yellow combo we saw on their site, which we must say looks brilliant on the Kawasaki. G4’s vinyl is impressively thick and durable. If you take the time to prep the plastic properly, it will last a long time.
So what do you get when you eliminate all of the external restrictions from the KFX450R’s engine and add on a pro caliber chassis and suspension setup? You get a machine that makes going fast really easy! At this level of tune, the KFX engine is one of the easiest to ride in the 450i class. While most uncorked 450s center their power from the midrange up, the Kawasaki’s power is focused around the bottom end and midrange. The power is a lot like stock, but thanks to HMF and Fuel Customs, there’s a lot more of it.
Power comes on sooner than most other 450s. It pulls with authority out of the hole. Then the power just keeps building with no abrupt hit, pulling hard throughout the midrange. Just as the motor begins screaming, you feel the power start falling off rapidly. You quickly learn to up shift a little sooner on the Kawasaki and it rewards you for it.
With such good low-end torque, you don’t have to carry as much momentum through corners with short runs at the next jump. This helps open up the inside line, creating more passing opportunities. If you’re a gear, or two, too high, the KFX engine could care less. It almost pulls like a big bore sport quad down low. There’s enough power in the midrange to hang with most local racers down long straights and over big jumps. You could lose drag races into turns, however, if you try and rely on the engine’s over-rev instead of up shifting. Ride the KFX a gear higher than the other 450s and you’ll get the most out of it.
The power signs off early, so we never found ourselves bounding off the rev limiter, which will help this motor last a good long time. Dave Trimble felt this was all the motor he needed to be competitive, and Chase was amazed at the difference between the stock and uncorked engine. Chase felt that National B riders and up may benefit from more top end power. Switching to KX450 dirt bike cams from 2008 make a big difference in the upper midrange and top end power, while maintaining Kawasaki’s standard for reliability. For most local racers, though, this engine is fun and easy to ride, allowing you to ride to your full potential, not being held back by a machine that is too much to handle.
The wider Teixeira Tech front end and Lone Star axle increased stability in corners and at high speed. With 4.125 degrees of caster dialed in on our Teixeira arms, coupled with long travel Race Tech shocks that don’t pack under hard braking, the nervous tendency of the stock front end was gone. You can charge corners harder with later braking thanks to the machine’s increased stability and steering predictability. Although high-speed stability was much improved, there was no trade off when it came to steering. This KFX can still cut an inside line with the best of them.
The KFX has a little taller backbone than some of the other 450s. This aids comfort and eases the transition between sitting and standing, especially late in the moto. The downside–– it also requires the use of more body English when cornering aggressively. Top-level racers may want to have their sub frame lowered to further lower the machine’s center of gravity. Hetrick Racing can help you with this modification if you really need it.
In the air, the KFX feels light and maneuverable. When you come in for a landing, the Race Tech shocks will take the big hits. Different suspension builders set their shocks up differently. We have found Race Tech to spring their shocks a little on the firm side. They are smooth on the downside and stiff enough to save the day when you come up short on a big jump. With a wide range of adjustment and a little tuning of the GS-3 shocks, our machine tracks straight in whoops and through choppy sections. They provide a predictable, confidence-inspiring ride, never kicking, deflecting, or doing anything unexpected to take you off your game. For fast smooth tracks with big jumps, these Race Tech shocks are on target. For loamy or sandy tracks that develop lots of chop, we might consider a slightly softer main spring up front.
Precision’s Pro model steering stabilizer did a superb job of keeping bumps to the front wheels from transferring back to the handlebars. Another benefit of the stabilizer is that you can actually use it to increase or decrease traction in corners for better hook up, or easier sliding. We will show you how in an upcoming test of the stabilizer.
The ITP Quad Cross MX Pro Lite tires performed beautifully at both test tracks, with both ends hooking up well in intermediate to hard pack conditions. In loam, you’ll run into some front end push and you’ll need to use precise clutch control on deeply tilled starts. For tracks that pack in, these tires can get you to the checkered flag first. With lightweight and excellent handling characteristics, they are a great race tire. For riders looking for a long lasting practice tire or a tire that will last for quite a few races, we would recommend you look into the original harder compound Quad Cross MX. The MX Pros don’t wear fast by race tire standards, but don’t expect to get half a season out of them.
The Kawasaki’s brakes continue to offer plenty of power, now enhanced with Streamline’s brake lines. We’re braking later on our modified Kawasaki, so the extra power is appreciated.
Dave and Chase both liked the ergonomics of the Kawasaki. The Precision Shock and Vibe bar clamp really helps isolate the handlebars from the vibration engine and aluminum frame. They also do a good job of reducing tortional impacts felt through the bars that can be painful to the wrists. The Shock & Vibe clamp raises the bars around 1 in., opening up the cockpit for taller riders. The Bling Star heel guards offer plenty of heel room, and although the stock seat is too firm for trail riding, it seems at home on the track.
Opened up, the Kawasaki has a competitive engine for most racers, with the kind of easy-to-ride power that allows you to make the most of it. The way our machine was set up, the chassis and suspension are more than a match for the engine, allowing you to push harder without getting in over your head. Chase summed up our feeling about this build best when he remarked, “I wonder why I don’t see more Kawasakis at the races.” If you take the time to set your KFX450 up properly for the track, we think you’ll be impressed with how well it works; your competition, on the other hand, may not share your enthusiasm.
|Exhaust||HMF Competition Series, Full Sstem||$555.95|
|Intake||Fuel Customs Intake with Airbox and Filter||$325|
|Fuel Module||HMF Fuel Optimizer||$249.95|
|A-Arms||Teixeira Tech +2.125in W/Needle Bearing Upgrade,Custom Kawasaki Green Powdercoat, and Chrome Finish||$1,345|
|Axle||Lone Star Racing, Axcaliber Pro Racing Axle||$399|
|Front Shocks||Race Tech, Long Travel Race Series with Piggybacks, hi & low speed Compression and Rebound Adjustable.||$1,599.99|
|Resr Shock||Race Tech, Race Series Remote Resy, hi & low speed Compression and Rebound Adjustable.||$1,099.99|
|Steering Stabilizer||Precision Racing Pro Series||$559|
|Front Tires||ITP QuadCross MX Pro Lite 20×6-10||See Dealer|
|Rear Tires||ITP QuadCross MX Pro Lite 18×10-8||See Dealer|
|Front Wheels||Hiper Technology Tech-3 8×8 (3+5) Single Beadlock||$234.99 each|
|Rear Wheels||Hiper Technology Tech-3 10×5 (4+1) Single Beadlock||$239.99 each|
|Front Brake Liknes||Streamline, Steel Braided Dual Line||$89.99|
|Rear Brake Line||Streamline, Steel Braided||$39.99|
|Brake Line Clamps||Streamline, Billet||$29.99|
|Rear Brake Clevis||Fasst Company||$39.99|
|Rear Brake Return Spring||Fasst Company Rear Brake Return Spring Kit||$19.95|
|Handlebar Clamp||Precision, Shock & Vibe||$229|
|Grips||Spider Slim Line SLT||$16.95|
|Nerf Bars||Bling Star Notorious||$196.95|
|Heel Guards||Bling Star Notorious||$193.95|
|Grab Bar||Bling Star MX||$61.95|
|Chassis Skid Plate||Genuine Kawasaki||$169.95|
|Swingarm Skid Plate||Genuine Kawasaki||$159.95|
|Number Plates||G4 Phoenix||$79.95|
|Lone Star Racing||http://lsracing.com|