We finally got a chance to ride the 2010 Suzuki RMX450Z for  the first time this week. This is probably the most important off-road bike of the year; not just because it’s the first mainstream off-road bike with fuel injection, and not just because it marks Suzuki’s first serious off-road machine in years. The new RMX is a major event because it is one of the only new machines born in an era of economic slow-down. Suzuki actually doesn’t have any official 2010 models in its current line up other than this and the two RM-Z motocrosser. That’s quite a statement of priority.
      Here’s what it is: an off-road version of the EFI motocross bike with electric start, lights, instruments, a kickstand, softer suspension and EPA approval. If you buy an RMX and you want to go racing, you have to do four things, all of which are chronicled in a  kit sold by Yoshimura. The first is remove the throttle stop and plug up the resulting hole in the throttle body. You then can remove parts to deal with a restrictive airbox and pipe. And finally, you electronically “rejet” the EFI system by plugging an aftermarket jumper into the wire harness. Yoshimura calls this the Cherry Bomb, and sells it for $40. Once you have made all four modifications, the bike runs like an RM-Z–almost. The cams still have a milder profile and  the rev ceiling is slightly lower. All of that is appropriate for an off-road bike.
      Suzuki used the same EFI system as the 2009 RM-Z, but with a smaller Keihin throttle body. Interestingly enough, the RM-Z’s capacitor starting system remains in place despite the fact that the off-road bike has a battery. The RMX uses the battery to light up the EFI’s brain normally, but if the battery is dead or even removed, the bike still starts and runs.  And here’s a strange tip: if the battery is low, you can disconnect it for easier starting.
      Along with the EFI system, the aluminum fuel tank was imported from the RM-Z. Unfortunately, it still has a capacity of only 1.6 gallons. It looks big, but it has to contain a rather large fuel pump. That pump has a sensor that operates a “low fuel” light when you’re about to run out of gas. In our world, 1.6 gallons is almost out of gas, but we’ll get over it.
      On the chassis side, Suzuki planned on using the 2010 RM-Z frame, but something funny happened on the way to the production line. Test riders (including Rodney Smith) said they liked the old frame better for off-road riding. They said it was more compliant and even said the motor felt more controllable in the old frame. To confirm it, they swapped frames several times, using the exact same test motor just to be sure. When they merged the 2009 frame with the 2010 swingarm, they said it was a magic combination. The RMX got softer suspension settings, of course, but the actual shock and fork components are the same as those of the motocross bikes.
      Suzuki brought the first eight RMX450s to the Medocino National Forest in Northern California for two days of riding. The ground was wet, the trails were excellent and it was love at first roost. Suzuki did a brilliant job with the fuel injection. It runs perfectly once the throttle stop was removed. It has almost none of the toggle-switch behavior that handicaps most EFI bikes right  above idle. It rolls on smoothly and, just as importantly, it rolls off gradually, too. Other EFI bikes toss you forward violently when you chop the throttle, then snap you back again when you go the other way. The RMX doesn’t stumble down low and rarely flames out. Even when you climb up to the snow line, the bike runs clean. Altitude is no longer a factor.
      But the Suzuki’s biggest advantage is its handling. Just like the RM-Z, the bike is excellent in turns. The front end sticks to anything and the effort required to turn is enough to make you really lazy. The bike whispers in your ear that it’s much lighter than a KLX, WR or CRF450X. This is probably a big fat lie. We haven’t weighed it yet, but it’s a safe bet that the Suzuki is a around 260 pounds without fuel. But regardless of what the scale says, your arms will tell you that the bike is easy to handle and feathery. You only feel the weight on steep hills and when you have to brake in a hurry.
      On the second day of riding we tried the bike with the Cherry Bomb and with the airbox and muffler modifications. It turned into a real racer. The bike developed a sharp mid-range bark and demanded more attention. But it also became obnoxiously loud. As soon as we get the bike on our own turf, we’ll try to find middle ground. Perhaps there are pipe modifications that don’t result in so much noise. Check out the next paper edition of Dirt Bike for a full report.
We tested the RMX in stock form and with Yoshimura’s $40 Power Bomb, which remaps the EFI for competition.
Suzuki did an excellent job of transforming the RM-Z450 motocrosser off road. The new RMX has some parts borrowed from the 2009 MX bike, some from the 2010 MX bikes and some all its own.

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