Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/634995
CN III ARCHIVES BY LARRY LAWRENCE A modern factory 450cc motocross bike produces about 60 horsepower. That doesn't sound like all that much until you realize the mo- torcycle only weighs around 220 pounds. That gives a motocross bike almost 50 percent more power-to-weight ratio than a Cup car and is not that far off the power-to- weight ratio offered by an Indy Car. And keep in mind with a motocross bike you have just one tire to try to transmit all that power to the ground, and you're on dirt! So it's easy to understand with those kinds of power figures that a factory 450 motocross bikes can be an unruly beast to try to ride. So powerful are today's motocross machines, that for the most part, instead of looking for ways to produce more peak power, motocross engine builders seek ways to spread out that power and make it more usable. The advent of the 450cc, four-stroke era has changed the way the riders ride and tuners tune, as opposed to the prior era's 250cc two-stroke powerplants. "Back in the two-stroke days you pretty much gave it all you had all the time, trying to get more power," said Jeremy Albrecht, team manager for Joe Gibbs Racing Yamaha. "Now there is so much power it's more about managing the power, it's getting the curve on the engine (charts) right, not being too aggressive. Each rider has their own preferences so you're still tailoring it. Both of our guys run different engine settings." Albrecht also points out that no matter how powerful the output of the 450 bikes are, there's always someone wanting more. "There are still riders who want more out there," he said. "It's really just the way that they ride and what they're looking for. We do a lot with ignition mapping. That's the way we tailor it to the wants of different riders." In the two-stroke era the factory teams would use a trick of using heavier flywheels to give the bikes more traction. Albrecht says that practice is still used today with the four-strokes. With that power comes cost. Four-strokes have added greatly to the price of racing in mo- tocross. Not only have the parts of a four-stroke engine, with valves, springs and cams, made the engines more costly, the teardown and rebuilds take much longer, so much so that most of the majority of the factory teams (and even some of the second-tier squads) now employ engine builders, whose exclusive job is to build and NOW YOU'RE PLAYING WITH POWER! P104