A newly designed cylinder head combined with intake and exhaust port tuning and crankcase revisions to achieve an approximate 5% increase in output.
The RM-Z250’s fuel injection system now features two injectors. Instead of using a single injector that can compromise low-end fuelling in order to supply enough fuel for top-end power, the primary injector delivers precise low-rpm fuelling while a secondary injector at higher rpm provides the extra fuel needed.
Fuel pressure is increased by 17% over the previous model and promotes the effective mixing of air and fuel, resulting in improved throttle response.
The Intake camshaft profile has increased lift for MY19 resulting in improved intake efficiency and increased power output.
The RM-Z250’s electronic systems work seamlessly with the rider to get the power to the ground. To maximise traction for conditions, the engine control module (ECM) automatically adjusts ignition timing and fuel injection based on throttle position, engine speed and gear position.
The new RM-Z250’s S-HAC monitors throttle position and gear position in order to adjust ignition timing for maximum acceleration through the three critical stages of a motocross start: the exact moment of launch, getting over the starting gate, and then powering up the start straight. Three settings are available, with A- mode intended for harder surfaces where controlling wheel spin is paramount, B- mode for normal dirt conditions with good traction, and an “off” setting.
The RM-Z250 is already known as one of the best-cornering motocross bikes available, but we went to work improving it even more for MY19. The frame and swingarm are all new, with the aluminium frame spars changing to a hollow square section that does away with an internal rib, shedding 370 grams while increasing torsional rigidity by 10 percent for better stability and bump absorption. Using a new hydroforming process for the aluminium swingarm permits a tapered cross-section without any welding, making the new assembly just as rigid with thinner walls for a weight loss of 80 grams.
The new KYB coil spring fork replaces the previous model’s PSF2 air fork. Featuring a unique design that provides a progressive damping setup offering excellent compliance over small bumps while firming up deeper into the stroke to handle bigger hits such as harsh jump landings. Upper and lower triple clamp design has been optimised for rigidity while cutting 60 grams. Out back, the rear suspension linkage ratio has been changed to firm up short stroke movement while optimising longer suspension action for better traction, and is 14.9 grams lighter. The fully adjustable KYB shock has an improved range of adjustment, and a spring with thinner but stronger wire (feedback from MotoGP technology) that is 370 grams lighter than before.
Riders can adjust the engine performance to suit varied track conditions. By plugging in either of two additional fuel-setting couplers, riders can opt for a richer-than-stock or leaner-than-stock fuel setting to make the most of any riding conditions. Included with the bike, these couplers can be easily plugged in trackside.