On paper, the KFX looks as if it should be near the top of the performance 450 pile and perhaps first for some applications such as XC-type racing. After all, it possesses some unique and high-performance features such as an aluminum frame, fuel injection, reverse, great handlebars and a whole list of things that just didn’t end up panning out on dirt. However, after our last Modified 450 Shootout, Kawasaki’s Pro 450 setup was clearly a front-runner. But most people do not have a massive budget to make this happen. This month’s KFX project explores different ways to take the Kawasaki to the front.
In stock form, the KFX450R is not likely to be king of the hill at your local drag races. It was also lacking on the MX track and needed more on the high-speed trails. We called on CT Racing to help with this problem. CT is known around the industry for creating solid power at a reasonable price. Here’s what they did for our KFX.
CT first mounted up one of their complete exhaust systems ($507.95) and sent the KFX directly to the dyno to find out how it performed. The CT Sonic pipe made a significant increase in horsepower, but as we suspected, the KFX with a pipe still fell well below Yamaha’s YFZ450 with a pipe and Suzuki’s LT-R450 with a pipe and Cherry Bomb.
To get the big horsepower out of the Kawasaki to do battle on MX tracks, WORCS races, and maybe even a trip to the sand dunes, we had to go into the motor. We spun the top-end off and stuffed a JE high-compression 13/1 piston in the cylinder. CT Racing honed the cylinder with their diamond hones. You want to be careful with the Nikosil cylinders and have a shop hone it with the correct stuff. If hones are used that have previously used on a steel cylinder, it washes and stuffs particles into the cylinder that won’t clean out. These contaminants only come out when you run the motor, and they hammer the cylinder and piston as if you ran dirt through the motor. JE offers a two-ring and a three-ring piston for this motor; we opted for the three-ring. The durability of ring seal is significantly longer with the three-ring pistons. Since you probably don’t have factory mechanics waiting to pull apart the motor every couple of rides, go for the three-ring setup.
The head was then pulled apart to clean, inspect and check the valves for trueness. CT then flow bench ported to extract massive flow characteristics, ensuring big horsepower over a wide curve. We re-used the stock valves, as they are titanium, and stayed with the stock valve springs to save on costs as well.
CT followed by using their five-angle radius valve job to seat the valves. The five-angle radius valve job rolls most of the angles into a radius, as opposed to straight-angle changes. This increases the flow characteristics. The idea behind five angles as opposed to the common three-angle valve job is to completely re-shape the valve seat all the way down into the port, blending the valve job to the port job, and also working on deshrouding the valve pockets in the bowl. This significantly increases the flow at low lift, enhancing power across the board. There is no downside to increasing flow in this fashion; you’re not trading bottom for top or anything like that. CT’s complete motor job runs for an impressive $615.
With the added compression enhancing the bottom-end power and the headwork offering another large boost, we needed a cam that would extend the rev without dumping the bottom-end power. Webcams’ Sonic Grind Cam ($192) was a good-quality and affordable option. This cam has an extended duration, so the KFX was pulling all the way to the rev limiter. Since the stock rev limiter was kicking in before the motor topped out, we installed a Dynojet ignition ($129.95). Dynojet’s ignition has a higher rev ceiling. After you purchase it, you have to contact Dynojet and they’ll give you access to extend the rpm to the desired amount.
THIS KFX SAID, “HELP! I CAN’T BREATHE!”
The upgraded motor package was asking for more air. The stock airbox is restrictive and needed to be replaced. Fuel Custom’s air intake system ($325) was the best setup on CT’s dyno. This is the same setup that was installed on our Modified Shootout KFX. Kawasaki pilots, Josh Creamer and Chad Wienen, also used Fuel Custom’s setup.
Fuel Customs offers an air filter-only setup, but it is so large that it won’t fit in the stock airbox. For sand applications where an airbox is not necessary, you can run it without the airbox. For our intended off-road usage, we chose their model with a complete high-flow airbox. This setup is shipped with a gauze-type, high-flow filter and an Outerwear. CT Racing has foam filters available for the Fuel Custom rigs as well. According to CT Racing, the stock intake tract is so bad that on a moderate build (pipe, cam, fuel management), the Fuel Customs gains 3 horsepower, and as the horsepower goes up with more mods, the stock intake holds back even more power, so larger gains are shown.
From the factory, the KFX is a bit twitchy and actually becomes extremely twitchy under hard braking. We felt that Kawasaki’s factory caster settings were part of the problem. The suspension also felt a bit soft for all of our testers, so that accentuated the problem under braking. We also needed width to serve our purpose of off-road racing.
Teixeira Tech’s long-travel A-arms ($1045) were installed. Our favorite part about the Teixeira A-arms is the caster adjustment system. All you have to do is loosen the upper ball joint and you can slide the ball joint forward or backward; the arms and ball joints have teeth built into them so that when you tighten them, they lock down and can’t move. This is a cool system, and one that let us add some caster to slow down the steering, which helps cure the twitchiness problem. Being easily adjustable, you can actually dial these arms in to your liking. The farther back you pull the caster, the more the quad will track straight, which is better for high speed. If you are racing or riding at higher speeds, try pulling the caster all the way back. If the terrain is more technical, try setting them in the center position, which is perfect for MX.
We had Clark Jones of Noleen J6 supply us with the Noleen J6 shocks ($1395, front; $895, rear). We have worked with Clark in the past, but you might recognize him as the man behind Doug Gust’s 2004 championship-winning Z400 suspension.
The main thing we needed was to keep the front end from diving, stop it from bottoming and not pick up a harsh ride in doing so. We installed the shocks and went testing. At first, the front end was stiff. It wasn’t the off-road ride we were after; it was fun at our local AV Motoplex. That track is very flat and smooth with big jumps, but we felt it was going to be a bit harsh for off-road, so we had Clark work it over again and ride test it himself. Clark was a Yamaha Factory support two-wheel rider back in the day and can carry plenty of speed on a quad himself to get things dialed in. He’s worked with Teixeira A-arms in the past, but not on the Kawasaki; so with our input and some testing, Clark got the Noleen J6 shocks close to our liking.
We added a DuraBlue eliminator 2+2 axle to add stability. DuraBlue has been making wide axles since before there were four wheels on ATVs. They also offer a lifetime warranty on their Eliminator axles.
We mounted Maxxis six-ply RAZR tires ($80 each), 21×7-10-front and 20×11-9-rear, on reinforced Douglas wheels for the trails. For MX applications, we went with a smaller Maxxis RAZR set ($55), 18×10-9-front and 20×6-10-rear. All four corners were mounted on Douglas aluminum wheels. To add some strength, and a little red powder-coated bling, we installed OMF beadlocks as well. The beadlocks look great and strengthen, but they also add cost. To save money, reinforced wheels are a good option. They also protect your wheels from dents and dings.
The stock handlebars are a little close to the rider, so we flipped the stem clamps, which moved the bars forward almost an inch. We went with a set of Fasst Flexx handlebars ($350), which really help cut fatigue. If you plan on lots of hours in the saddle, this is the best way to go for bars. We used their 14/31 low bend on this quad. It’s very similar to a CR high bend, which is a very popular ATV bend.
The seat is so hard that it could be used to fill a pothole on a highway, so we traded it in for a QuadTech seat foam and cover ($170). You won’t believe the difference it makes.
We also installed ASV levers, which are easy to pull, adjust on the fly, are virtually unbreakable and are adjustable for any hand size. And to top it off, they look awesome! Soft compound Spider Grips ($15.95) were added as well.
Since we were to spend half our time on the motocross track, X-Factor nerf bars with heel guards ($253.99) were installed. Many of the aluminum heel guards on the market are too close to the rider’s heel, not allowing enough room for our big-footed testers. These nerfs had plenty of room, and the gnarly teethed pegs provided great traction. We also installed an X-Factor front bumper ($119) to give us an aggressive appearance.
While we wanted to eliminate most unnecessary costs, we couldn’t help but add a little bling to our KFX. Could you blame us? Performance Carbon’s cool carbon fiber bits helped here. We added carbon fiber rear fender extensions, short race style front race fenders and the cowling under the nosepiece.
Even though our revamped KFX450R’s intended use was for high-performance off-road, we tested on both MX and in the rugged desert. On our initial test, we found the suspension to be plush yet firm enough not to bottom out in the rough terrains unless you just overdid it. The A-arms with the caster pulled back kept things tracking straight with little effort. The stock, twitchy feeling was close to eliminated, resulting in overall handling characteristics that provide a good ride on the tracks and trails.
With all of the modifications that CT made to the engine, the power was now very linear. It produced good bottom-end power and was strong all the way to the rev limiter. After putting in some time on this motor, we all agreed that this is the kind of power delivery that makes it easy to make a quad go fast. The power is smooth and fast. We’ve been finding the fuel-injected motors—even with big horsepower like this Kawasaki with over 55 rear wheel horsepower—to be less abrupt compared with a carbureted motor wit the same horsepower. On the track, we could pull second gear starts and the still lift wheelies in fourth gear.
Our goal was to make an acceptable and competitive off-road quad for a reasonable amount of money. So just to be clear, our objective was not to build an over-the-top MX racer, but rather to drastically improve its performance for a reasonable amount of money. Hopefully, our tinkering might help lead you to buy a Kawasaki or even show you how you can tune yours up. If you want to see this KFX perform with your own eyes, be sure to log onto www.dirtwheels.com for video footage that we put together just for you.