Honda has unveiled its revamped 2015 motocross models, the CRF450R and CRF250R. Release date and Australian pricing is yet to be announced.

The 2015 Honda CRF450R has a host of upgrades, headlines by a new cylinder head for improved top-end power and added over-rev. The exhaust has a larger diamater also for top-end, which is shorter and closer to the bike’s centre of mass.

It has revised ignition map settings and new settings for the dual-timing PGM-FI fuel injection. Peak power hits earlier in the rev range and continues longer than before. A new piston is stronger due to a new heat-treatment process.

New ACG flywheel incorporates more mass for smooth power delivery and enhanced low-end response, and makes it less prone to stalling or flame out. Transmission gears are stronger.

A new Engine Mode Select button allows the rider to easily select one of three different EFI/ignition maps, plus a HRC accessory tuning tool can be used to program custom maps actuated by the Engine Mode Select button.

The throttle return spring has a lighter pull, as does an updated clutch cable design gives a lighter pull at the lever.

Handling-wise, the 2015 Honda CRF450R has a new lighter second-generation KYB Pneumatic Spring Fork (PSF2), which features five ways to adjust performance: high-speed and low-speed adjusters for both rebound and compression damping settings, plus air-spring adjustability. The rear shock adjuster is updated for rebound damping settings, now located for more convenient access.

There are now front/rear wave-style rotors with a larger 260mm front brake disc, with the front brake guide and radiator grill now featuring a black finish. The fork covers are also updated, and Honda has fitted new-generation Dunlop Geomax MX52 tyres.

As for the 2015 Honda CRF250R, it boasts the all-new production version of the 49mm Showa SFF-AIR Fork. Like the CRF450R, it has the Engine Mode Select button, lighter throttle return spring, larger brake discs, black front brake guide and radiator grill, new fork covers and Dunlop’s Geomax MX52 tyres.

There’s a larger-diameter exhaust system and new fuel-mapping settings, which increase engine performance for smoother acceleration, improved throttle response, quicker revving and more peak power.

Plus, the Pro-Link rear suspension uses a single shock now equipped with a lighter and stiffer spring.