Race sled undergoes
BRP’s 2012 version of the Ski-Doo MX Zx 600 RS will see improvements in engine and chassis performance. The engine, front and rear suspensions and drive train were all changed with sno-cross and cross country racers in mind.
Headlining the list of changes is the new engine, which delivers an additional 6 hp and better throttle response across the entire operating range. The list of new components is lengthy but starts with a new crank case, a new patent-pending crank shaft design and new cylinders — all directed to provide better flow and higher horsepower.
The engine is designed to be very efficient from 8,300-8,800 rpm with a broad powerband. A new fuel pump and hose routing improves fuel delivery, and new ECM calibrations will complete the power pack.
The front suspension was also analyzed for ways to improve chassis performance and balance to better match up with the new skid frame that was introduced last year. The change to new, taller spindles improves ski pressure and cornering, while the new powder coating will reduce any snow or ice build up.
A redesigned steering post and bushing further reduce any bump steer to non-existent. Finally, a new upper A-arm creates a new steeper caster angle and rounds out the geometry package. Racers will notice much straighter tracking through the bumps and better chassis balance front to rear.
The rear suspension was introduced last year as “PCX,” but that was only intended to disguise the rMotion name until the consumer version was introduced. For 2012 the rear suspension is named rMotion Racing. Both skid frames share the same basic geometry, featuring a rising rate rear shock and long front arm, but each are optimized for their intended uses. The rMotion Racing has a new reinforced rear arm, improved coupling system and new reinforced powder coated rails for reduced ice build up.
Once all the new parts were put together, significant time was spent on chassis calibration. All four shocks have been re-worked to deliver more compliant performance in small bumps for less rider fatigue, yet still handle the nasty kickers and big jumps. The drive train changes were aimed at improved belt and clutch performance to deliver consistent RPM and performance lap after lap.
The new engine mounts are stiffer to keep the clutches better aligned, and new specs for the secondary clutch will allow it to float a little to improve belt life. There’s better venting to the clutches, reducing power robbing heat, and the belt itself is new construction for durability and performance. The deep 19/49 gearing will pull hard to the first turn and optimize clutch calibrations for sno-cross set-ups. The driveshaft mounted brake will also get better venting for cooler running.
Finally, the look of the machine changes with a new black powder coated tunnel to further reduce ice build-up and provide a stealth look, along with new graphics and coloration.