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Fuel Customs Kawasaki KFX450R Intake and Air Box Test

Want more power from your KFX450? This is the number one product you’ll need!

Former Kawasaki Team Manager and Pro ATV Racer, Jimmy White, spoke highly of Fuel Customs intake.

A while back we outfitted our KFX450R with a slip-on HMF Competition Series exhaust and Fuel Optimizer, resulting in more power, especially in the bottom end and midrange.   When it came time to turn our mildly built trail machine into a motocross racer, we knew we wanted even more power. Former Kawasaki Team Manager and Pro ATV Racer, Jimmy White, spoke highly of Fuel Customs intake. We tested a notably more powerful KFX, put together by CT racing a while back that featured one.  CT owner, Allen Knowles, raved about the difference the Fuel Customs intake made during testing with CT’s exhaust, and the difference it made in allowing him to extract more power out of the engine.

For our MX built, we wanted to wring as much power out of the Kawasaki’s engine as possible, using only external bolt-on parts. Since we had not addressed the Kawasaki’s restrictive intake, we were hoping the Fuel Customs intake would be our ace in the hole for producing more power.

We liked HMF’s slip-on Competition Exhaust and wanted to carry it over to our motocross build.  HMF felt its slip-on was fine for riders using stock intakes. However, with the Fuel Customs intake, they felt we’d see bigger gains with the full Competition system’s freer-flowing head pipe.

Technical Stuff.

CLICK FOR VIDEO of the Fuel Customs intake test

For the KFX, Fuel Customs makes intake kits with an open air-box, or with filters that simply clamp onto the end of the intake. We ordered Fuel Customs intake system and air box for some extra filter protection from beneath. Fuel Customs makes intake kits that work with stock air boxes on some models. Company owner, Garrett Torres, told us, “We only build air boxes for models where the stock air box is restrictive.” Obviously, the KFX450R was one of them.

The kit comes with the intake itself, which is designed to boost intake velocity for improved throttle response. The stock intake has a congested 90 bend, which creates a bottleneck for incoming air. In comparison, the Fuel Customs intake has only a mild curve and is almost as big around as a soda can at the smallest point.  Residing in the air box is Fuel Customs 8-ply cotton filter with Outerwear pre-filter, which they claim maximizes protection from dust and dirt. There is a little 90-degree prong that attaches to the stock breather tube that Fuel Customs left out of our package. We contacted them and they had it to us in no time.

Installation would have been pretty straight forward if our kit had come with the correct filter. Instead of sending the filter for the KFX, Fuel Customs sent us the filter for the YFZR. After spending a half hour figuring out the filter debacle, we ordered the right filter from Fuel Customs and wrapped up the installation a couple of days later. With the right filter, installation should take less than an hour.

The Test

When we first started the Kawasaki, the Fuel Customs intake leaned the motor out so much that it would hardly run. We had to crank the output on our HMF Fuel Optimizer to achieve the proper air fuel mixture to compensate for the dramatic increase in airflow. HMF’s tech department gave us a recommended Fuel Optimizer setup to try, which seemed to perform very well with the new intake and head pipe.

Hitting the track, we were expecting a mild increase in top-end power, but what the Fuel Customs intake does for the KFX450R is nothing short of dramatic.

Hitting the track, we were expecting a mild increase in top-end power, but what the Fuel Customs intake does for the KFX450R is nothing short of dramatic. If you have an aftermarket exhaust and fuel controller on your KFX, remember the difference in performance you felt when you first added them to your machine. Well, adding the Fuel Customs intake is like getting that gain all over again!

With the intake, the Kawasaki pulls harder down low and enjoys a significant increase in midrange power. The increase in intake velocity really adds snap to the KFX’s throttle response, which comes in handy when you want to break the rear end loose, or when you need instant power for short runs at a jump you need to clear.

With the intake, the Kawasaki pulls harder down low and enjoys a significant increase in midrange power.

The new intake provides plenty of air to let your motor breath when the throttle’s pinned, but if you really want your KFX to pull hard up top, you’ll need more aggressive cams like the ones out of the 2008 KX450 dirt bike. With stock cams, you get a bottom-end and midrange motor. With Fuel Custom’s intake, though, you get a lot more of it.

Sliding the filter over the intake and tightening the metal band is a little more difficult than removing and reinstalling the stock filter. Also, we wish that Fuel Customs would offer a foam filter option for their kits. Fuel Customs stands by its filters, but most motor builders we know and trust only recommend this style of filter for sand applications, preferring foam filters in the dust. If we get too concerned, we will just run a foam pre-filter.

Dune, desert, and motocross guys will do well with the roost protection the Fuel Custom air box provides for the filter. Cross Country racers, on the other hand, will need to add some tape to the top of the box in wet conditions.

Conclusion

The KFX450 intake is available with or without Fuel Custom's lidless air box.

Fuel Customs intake transformed the Kawasaki’s engine from trail friendly into a friendly racer. It will help you maximize the power potential of your engine with each new performance modification you add, whether it’s an exhaust system, or a full national motor build. If you are serious about making power with your KFX, Fuel Customs intake is the number one product you’ll need!

Manufacturer: Fuel Customs

Item: Fuel Customs Intake

Price: $325.00

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