Updated new quarter-litre off-road contender officially unveiled locally.
Yamaha Motor Australia has revealed the latest 2018 Yamaha WR250F domestically featuring updates to both the engine and suspension package ahead of the new year.
With DNA lifted straight out of the multi-time MX Nationals MX2 championship-winning YZ250F, the 2018 WR250F benefits from a range of important technical changes that are aimed at delivering increased performance and enhanced ride-ability.
The WR250F’s innovative reverse cylinder head offers many advantages over a conventional design. These include increased intake and exhaust efficiency, as well as enhanced mass centralisation thanks to the use of a top-mounted air-filter and under-seat fuel tank.
For the 2018 model year Yamaha’s engineers have taken this cutting-edge technology to the next level and developed a new reverse cylinder head that offers even stronger mid to high RPM pulling power.
For an increased flow of fresh air into the four-valve head, the intake port’s position is raised and the intake valve diameter is increased. New higher lift intake and exhaust camshafts give increased valve lift for a stronger feeling in the mid to high RPM range – while for enhanced low to mid-range performance the intake camshaft’s working angle has been narrowed.
Stronger intake and exhaust valve springs are fitted to correspond with the use of new higher lift camshafts and to accommodate the increased engine performance, a newly-designed nickel-chromium-molybdenum steel con rod is used for the 2018 model.
The piston has also been covered with a DLC coating to reduce friction, while the piston top has changed from pent roof to flat. The new design results in a piston that weighs seven percent less with a gudgeon pin that is 18 percent lighter.
To achieve an optimal intake/exhaust balance, the twin exhaust ports have also been redesigned, and the snaking exhaust header pipe is equipped with a new larger diameter front section. As well as featuring a bigger bore pipe, this front section also benefits from larger radius bends, giving a greater internal cross sectional area that creates a much stronger exhaust pulse effect.
To match the increased engine performance produced by the redesigned cylinder head and high efficiency intake and exhaust systems, the 2018 YZ250F is equipped with a newly developed ECU with revised ignition timing and fuel- injector mapping. The new ECU cuts in at higher rpm, and features a rev limiter that gives an improved over-rev feeling.
Riders of all abilities can also use the optional Yamaha Power Tuner to adjust the WR250F’s power characteristics. This compact device plugs straight into the bike without the need for a PC, and enables the rider or mechanic to fine-tune the engine performance in seconds to suit the track conditions.
In order to handle the updated engine’s increased performance, the 2018 WR250F is equipped with modified high-strength crankcases. While their exterior shape and construction is identical to the 2017 model, the aluminium die-cast cases on the 2018 model have been subjected to a heat treatment process that increases strength by around five percent for a high level of reliability and durability.
One of the more visible differences to the modified high-strength crankcases is the absence of a kick-starter system, which saves close to one kilogram. Although removed from the 2018 WR250F as standard, the kick-starter will remain available as an optional accessory.
Made possible by the use of the reverse head engine, the WR250F’s top-mounted air-box and under-seat fuel-tank help to centralise mass for agile and responsive handling. The chassis changes introduced for 2018 include a revised balance of frame rigidity, together with refined suspension.
Using feedback from Yamaha’s factory teams, the updated 2018 frame has been fine-tuned in order to ensure that WR250F riders are able to fully exploit the increased engine performance of the updated model. The new frame is around 12mm wider in the area behind the swingarm pivot point, and this increased torsional rigidity ensures a higher degree of handling stability.
The 2018 WR250F also features specially designed front and upper engine mounting brackets that have been developed to compliment the characteristics of the free-revving 250cc engine. By using 8mm thick steel for the two front brackets, with 6mm thick steel used for the upper brackets, the WR250F’s new frame delivers a better overall rigidity balance for improved handling performance and ride-ability.
Increased ride-ability and comfort has also been achieved on the 2018 WR250F through a number of revisions to the front and rear suspension. The Air Oil Separate (AOS) KYB forks feature slightly reduced oil capacity and new factory suspension settings to give improved rider feedback and improved stability in ruts, bumps and corners. The fork tubes now includes a scraper which gives added protection to the oil seals, especially in muddy conditions.
For improved brake feel, the 2018 Yamaha WR250F now also receives a front disc rotor that has been increased in size from 250mm to 270mm. This update matches up with the increased engine and chassis performance giving total braking confidence on the fastest trails.
The new 2018 WR250F also features new graphics, as well as blue rims. For the Australian and New Zealand market only, the model comes with a competition off-road kit so owners can choose between full ADR compliant with road-legal indicators and mirrors or off-road spec for closed course competition. The Australian-only off-road kit now features a new lightweight Polisport headlight and lightweight Barkbuster hand guards.
Coming in at a recommended retail price of $12,199, the new 2018 Yamaha WR250F is set to hit Australian shores this October. Head to www.yamaha-motor.com.au for more details upon release.