The 2014 Yamaha YZ250F now has a rear-slanted
engine like the YZ450F.
Yamaha’s move to a rearward slanted engine layout should come as no surprise really, as the YZ450F has run the configuration since 2010. Frankly we are surprised it took this long for the Tuning Fork company to make the switch. The bore and stroke are identical to the 2013 model, but Yamaha claims this new iteration makes more power in the mid- to-high rpm ranges.
Most of the power gain is thanks to the updated electronic fuel injection. A 12-hole injector feeds a 44mm throttle body, while the entire system monitors throttle position, intake pressure, intake air temperature, crankshaft rpm and coolant temperature to deliver the correct fuel and timing parameters. Yamaha claims that the EFI system increases peak HP and that it also gives a more consistent throttle response. To you and me that means no more carb bog on G-outs and harsh landings. Additionally, the Yamaha Genuine Accessory’s GYTR Power Tuner is compatible with the YZ’s ECU for custom mapping.
Just like the 450, the YZ250F now has a straight port down draft intake design with the airbox and filter placed where the fuel tank would normally reside. Airflow from the airbox has an almost straight shot into the dual overhead camshaft head. Airbox access is quick and easy with the removal of three 8mm bolts.
Spent exhaust gases exit the rear of the head into the new exhaust system that wraps around the engine rather than coiling behind it. This allows the silencer to be positioned 190mm (7.2 inches) further forward than before, helping centralize the bike’s mass making for better handling.
A new transmission sees revised gear ratios and the shift mechanisms have been reworked to reduce drive-force loss with smoother operation. The clutch has also been modified for better actuation and controllability.
The exhaust of the 2014 Yamaha YZ250F wraps around the engine. The new model also gets a new aluminum frame and subframe.
With the airbox moving forward and the exhaust pipe snaking around the engine rather than behind it the fuel tank needed a new home, so has been moved under the seat to further centralize mass. The filler cap now resides under an easily removable front seat section, giving the YZ a completely smooth transition from the riders perch to the front of the bike. Surprisingly, the fuel capacity has increased from 1.6 to 2 gallons.
Yamaha’s development target for the YZ250F’s chassis was for instinctive handling and class-leading suspension performance. To meet that target, the YZ250F gets an all-new frame. The dimensions are very similar to the 2013 model, but the thickness of the frame rails have been tweaked for rigidity balance. The swingarm mounting area is revised and the position and shape of the middle rail spars has been changed. The top engine brackets are now steel while the bottom brackets are aluminum.
In the suspension department, Yamaha has not jumped on the air-fork bandwagon and retains the KYB Speed-Sensitive System, but with changes. The rigidity of the outer tube has been altered and the inner tube gets a new surface coating. At the rear, the shock’s reservoir has been moved to the left side of the bike to make room for the fuel tank and more compact silencer layout. Of course the valving and spring rates have been optimized for the new chassis as well.
The 2014 Yamaha YZ250F is available in Team Yamaha Blue or a white and red color scheme. Both models now have “in-mold graphics” for better durability and reduced scratches to the radiator shroud. The white/red model also has black wheels and a gold chain.
Dealer availability is slated for October, and the MSRP is now $200 higher at $7,490.