Honda won the motor war with the only bike to top 50 horsepower during our dyno runs. As you can see, Anthony was pretty happy with the CRF.
The Kawi and RM-Z received the same score for motor performance but reached their marks through different ways. Both Rondon and Mandahl ranked the KX450F second, praising the linear powerband and ease of use as its strongest features. I agree that it was the easiest to ride for long periods of time, but I actually preferred the Suzuki powerplant over the entire group.
Riding the yellow bike was very similar to the KX-F in terms of power delivery, but it had a bit of a surge in the midrange that really made it fun to ride. Usually I would shy away from a midrange hit, especially on brutes such as these, but the RM-Z managed to retain its controllable nature while providing that extra bit of adrenaline. Doling out 48.5 and 49.3 hp, respectively, the RM-Z falls just short of the Kawasaki on the dyno but that single top-end pony is tough to detect on the track.
Each motor follows the four-valve, DOHC configuration, producing 449cc of displacement, with the exception of the
Honda which uses a Unicam, four-valve orientation. However, that's about all the ATK has in common with the other three.
Instead of the normal rear-mounted carburetor and forward facing exhaust port, the cylinder is reversed on the American bike. In place of the carb, ATK uses an electronic fuel-injection system to deliver combustibles. It's located opposite conventional carb placement and is at the front, between the enormous single-piece radiator and cylinder. The cool thing about EFI, though we didn't get to toy around with it, is that the system's computer can be remapped to suit a variety of conditions. The ECU also has a diagnostic hookup for monitoring precise engine performance information.
According to the Two Brothers Racing dyno, Honda ruled the horsepower chart while the fuel-injected ATK brought up the rear. We included some figures for the Yamaha YZ450F as well which demonstrate how competitive the motor is. Too bad we're not cool enough to get one.
Because we got the ATK through our local dealer,
Oregons Best Cars it was the only manufacturer that wasn't represented by a trained technician. Having someone there would have been ideal to help set up its suspension and to simply help explain some of the ass-backwards engineering found on the ATK. However, the U.S.-made motor ran like a champ even if there was a lot of engine noise. Engine braking was the most notable of the group thanks to its 12.5:1 compression ratio, easily the highest of the bunch. But the bike never sputtered or coughed and not once did it backfire under deceleration.
Despite the excellent running condition of the motor, all of our test riders noted that it was drastically underpowered in comparison to the Japanese bikes. Producing a mere 45.5 hp at the
Two Bros shop, the shortcomings were only magnified on the track by a significant amount of extra poundage courtesy of the only electric-start components. A docile motor coupled with excess weight gives the ATK more of an off-road bike characteristic. The bike is actually the same as the 450 Enduro but the off-road model has a revised ignition mapping and includes lights. We'll be testing the altered settings later in our 450 enduro shootout.
Even though we didn't get to test the Yamaha, we were able to grab some dyno numbers from the guys at Two Brothers simply for a quick comparison. The YZ450F they tested, which was sitting there mocking us, pumped out 50.2 hp and 33.9 lb-ft of torque. That horsepower figure falls beneath only the mighty Honda, and just barely, while the torque output lands it in third behind the 34-plus figures of the CRF and RM-Z. Don't you really wish we'd have gotten to test it now?
Motor Ranking:
1. Honda
2. (tie) Suzuki, Kawasaki
4. ATK
