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Tyler Bowers has been on the professional racing scene since he turned 16. Now 23, he has racked up three AMA Arenacross championships, a Monster Energy Supercross 250-class main-event win and is the current Costa Rican Outdoor National champion. Most of Bowers’ success as a professional has been aboard green machines. Casey Huntley, team manager of the Marisol Rios Reid/Pasion MX team, gave us an opportunity to throw a leg over Tyler’s Kawasaki KX450F race machine before it headed south to Costa Rica.


Pro Circuit has a huge role in making Tyler’s bike a reality, touching almost every part along the way.



A brand-new engine is completely disassembled and inspected for casting imperfections or manufacturing defects. Transmission parts are isotropic-finished. The cases are cleaned up, matched and reassembled, while the head gets worked on.

Team manager Casey Huntley told us their main goal when building this bike was efficiency: “Tyler is a big, strong guy and can handle loads of power, but he still has to hang onto the bike for 30-plus minutes twice in one day.”

The head has copper valve seats, titanium valves (both intake and exhaust), PC cams and valve springs. Other engine modifications include a high-compression piston, coated wrist pin, water-pump housing with high-flow impeller, and complete billet-aluminum Hinson Racing clutch kit with Pro Circuit’s heavy-duty clutch springs. The GET ignition box is programed to run with VP’s MR12 only. MR12 is illegal to run in AMA motocross or Supercross events, but since Pasion MX races in Costa Rica, it’s 100 percent legal and offers big performance gains.


Showa’s A-kit of the Single Function Forks (SFF) is bigger in diameter than the stock forks, and teamed with Pro Circuit’s solid-mount triple clamps, the system is designed to flex less. Bones at Pro Circuit re-valves and re-springs both the front and rear to match Tyler’s weight. Titanium nitrite coating (turquoise) upgrades are done on the fork legs and shock shaft to reduce friction.


As with any top-level race machine, there is a host of bolt-on items that add performance and rider comfort. The team uses Works Connection axle blocks, a clutch perch, holeshot device, engine plugs, brake caps, rotating bar clamp, extended-coverage aluminum skid plate, radiator braces, throttle tube, hour meter and hour meter bracket. Kite hubs are laced up to DID Dirt Star rims by Dubya USA. Tyler prefers 997-bend Twinwall Renthal bars with medium, full-diamond grips and an SDG-ribbed gripper seat cover. Galfer’s Tsunami 270mm oversized front-rotor kit adds braking power. Just like factory Kawasaki, the Pasion MX team uses the complete Moto Tassinari Air4orce intake system. Split Designs tops off the build with a custom race-team graphics kit.



Tyler Bowers’ Pasion MX KX450F was definitely not what we had expected out of a racing effort based in Costa Rica. The Pro Circuit engine package made loads of power throughout the power curve, but somehow managed to make it rideable. The lack of a violent hit was a huge surprise, allowing easy cornering and making getting over any jump a piece of cake. The clutch pull was a little stiffer than we would like, but Tyler says that’s normal; he prefers the feel of the Pro Circuit heavy-duty clutch springs. Most of the shock value came in the suspension department. We were expecting stiff, harsh and unrideable, and what we experienced was smooth, connected and predictable. The combination of Showa’s A-kit forks and solid-mount Pro Circuit triple clamps up front gives the KX450F a connected-to-the-ground feel so you can feel every little movement it makes. Front-end flex is almost completely eliminated. This was a huge shock to us at first and was definitely not something we raved about when riding back to back with our stocker. After a couple of test sessions, we came to appreciate the heightened feel of the front end. It allowed us to attack the track harder because we could feel exactly what the bike was doing. The rear shock was similar to the forks, having a very connected feel, but had some added plushness built in. This put huge smiles on our faces. One bolt-on item that really surprised us was Dubach Racing Development’s radiator lowering kit. The kit on Tyler’s bike was actually 24mm, similar to the Yamaha YZ450 kit Dubach sells. The nice thing about Tyler Bowers’ KX450F is everything is available to purchase for the retail public. So if you have a big enough bank account, you, too, can ride the exact same bike! For more information on the Pasion MX KX450F and complete build list, go to

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