With an all-new engine, new frame, new bodywork, electric start, Power Tuner app and more, the 2019 YZ250F is ready to roost the competition with features never before seen in the 250 cc class.
POWER TUNER APP
Yamaha broke new ground when the Power Tuner app was introduced on the 2018 YZ450F, putting flexibility and precision tunability into your smartphone. This technology carries over to the 2019 YZ250F, allowing riders to make fueling and ignition timing changes instantly and upload them to the bike via the onboard Wi-Fi system. It's the ultimate in trackside tuning!
The updated, fuel-injected engine delivers outstanding engine character with a focus on top-end power delivery.
"Reversed" liquid-cooled, 250cc, DOHC, 4-valve (titanium), single-cylinder engine with fuel injection.
- excellent "ride ability and controllability"
- broad power from low rpms right through to high rpm with excellent power characteristics
Rearward slanted, reversed cylinder design.
- rearward slant moves a significant amount of rotating weight toward the centre of the chassis, centralizing mass for light, agile handling
- cylinder angle reduced one degree to 5.2 degrees to accommodate new frame
"Reversed" engine design (FI system is front mounted, exhaust exits from rear of cylinder).
- FI throttle body and air box are front mounted, providing a straight downdraft intake path
- straight shot intake path provides optimum fuel / air / exhaust flow for excellent power
- front mounted intake keeps fuel cooler since engine heat has less effect on incoming fuel (cooler fuel is more dense and increases power)
- design also helps centralize mass for light, agile handling
4-valve cylinder head features a 13.8:1 compression ratio.
- 4-valve design offers optimum flow and excellent power
- compact combustion chamber provides optimum combustion speed while also reducing heat and power losses
- revised shape increases mid-to-high-rpm power
Lightweight titanium valves.
- valve, valve spring and lifter dimensions revised for mid-to-high-rpm output
- 31 mm titanium intake and 25 mm titanium exhaust valves with load reduced valve springs
- load reduced valve springs reduce internal power losses
- titanium valves reduce weight and improve performance... titanium valves are 40 to 45 % lighter than steel valves
- reduced valve weight improves valve train reliability and longevity
- reduced reciprocating weight allows for a higher rpm limit and better control of the valves
Automatic cam chain tensioner.
- reduces maintenance and mechanical engine noise
- special cam chain "sliders" reduce internal friction losses
- new compression ring stabilizes chain flutter
- new chain guide material better absorbs impact of chain
High lift intake and exhaust camshafts.
- strong power with excellent "control-ability"
- hollow design reduces weight
- revised cam profile improves mid-to-top-range power
"Liner-less" lightweight aluminum cylinder features a ceramic composite coating applied directly to the aluminum block.
- ceramic coating sprayed directly on aluminum block, eliminating the need for a heavy liner and therefore reducing weight
- excellent heat dissipation for consistent power delivery
- coating enhances the thin film of oil between cylinder and piston, reducing friction and increasing power
Cylinder "cutaways" allow air "trapped" under the piston to enter a special side chamber (cutaway).
- reduces horsepower-robbing "pumping losses"
Light, rewoked crankcase
- number of crankcase bolts, bolt length and gasket material reduced for weight reduction
- "cutaways" reduce horsepower-robbing "pumping losses"
- crankcase cutaways match cylinder cutaways for maximum efficiency
Lightweight, short-skirt, forged aluminum piston with bridge-box design.
- flat-top piston with lateral ribs on both sides of the piston pin area for strength and durability
- single compression ring and specially designed oil control ring increases the surface contact area for better sealing
- 2-ring design decreases sliding resistance, reduces weight and provides faster throttle response
Lightweight piston pin with diamond like coating (DLC).
- reduces internal friction
Piston oil cooler jet nozzle directs oil to the desired portion of the cylinder and underside of piston.
- reduces piston, cylinder and rod temperatures for excellent durability
Ball bearing style crankshaft.
- heat treated for strength and durability
- balance ratio of the crank has been optimized to reduce vibration
Nickel-chromium-molybdenum connecting rod.
- excellent strength and durability
- molybdenum coated thrust washers on either side of the rod to reduce friction
Lightweight gear driven counter balancer shaft.
- reduces vibration for improved rider comfort and less rider fatigue
- setting modified for 2019 for improved power feel
5-speed transmission utilizes a 2-bar, floating shift guide system and a 14 mm shift shaft.
- gears ratios are matched to engine power
- floating shift guide system provides smooth, positive shifts
- 14 mm shift shaft provides good durability in the event of a crash
- new lightweight gears and selector drum
- gears, dogs and shift mechanisms designed for smooth gear changes and improved durability
Heavy-duty, clutch with quick access magnesium outer cover and on the fly "barrel" adjuster.
- larger-diameter clutch for 2019 boosts reliability in high-heat conditions
- number of plates reduced for extended lifespan and improved feel
- quick access, lightweight, magnesium outer cover provides fast and easy clutch access
- light lever pull for reduced hand fatigue during a long moto
- works-style lever mounted "barrel adjuster" for on-the-fly clutch lever free play adjustments
New advanced 44mm Mikuni throttle body fuel injection system.
- high-pressure electric fuel pump feeds a new 12-hole Denso injector for optimial fuel atomization and air/fuel calibration, improving rideability
- new, compact throttle body is 12% lighter than previous unit
- FI benefits include automatic adjustments to insure the optimum fuel/air ratio regardless of outside air temperature and altitude
- other benefits include excellent starting and instant throttle response
- cold start knob also doubles as an idle adjuster
Injector spray pattern, spray direction and distance to the intake valves have been optimized.
- forward mounted straight intake tract maximizes benefits of the FI system and improves power output
Exclusive Power Tuner app.
- Groundbreaking technology brings the power of the GYTR Power Tuner to your iOS or Android device
- onboard wifi allows adjustment of air/fuel mixture and ignition timing maps based on track conditions
- record race log information and monitor a range of data such as maintenance and system diagnosis, engine run time and more
- CCU is adopted to accommodate new Power Tuner
New Electric Starter System.
- compact, electric starter system minimizes restart delays on track
- powered by a high-capacity, ultra-lightweight, four-cell lithium-ion battery for minimal weight
- kick starter is removed for reduced weight
Two-mode adjustable engine mapping.
- engine character can be adjusted with the push of a button
Forward-mounted airbox with features a washable, dual-stage, foam air filter.
- new clip-type fastener reduces maintenance time
- no tools required to access air filter
- washable foam filter reduces tune up costs
- new filter cover with Dzus fastener provides tool-free access
Wet sump lubrication system with "cartridge-type" oil filter
- reduces weight (no remote oil tank or oil lines)
- oil volume is optimized to reduce oil related drag and weight
- fast and easy oil changes
New compact, lightweight, single-core, dual radiators.
- larger and relocated radiators improve cooling during tough race conditions
New impellor and water pump.
- structure and pump shape changed to reduce stone chip damage and improve durability in race conditions
Maintenance-free transistor controlled ignition (TCI).
- produces a strong spark for fast starts
- provides precise ignition timing / mapping for optimum engine performance at all rpms
Updated wrap-around exhaust.
- exhaust exits from the rear of the engine and circles cylinder body
- wrap-around design ensures the optimum tuned header length
- design maximizes exhaust "pulse effect" for excellent power delivery
- centralizes mass by moving weight closer to the centre of the chassis
- shape change for 2019 improves power and feel
- new muffler shape
New Lightweight, aluminum, re-packable muffler (aka silencer).
- sound output is 94 dB meeting CMRC and AMA regulations
- muffler is re-buildable for optimum performance and reduced noise levels
Special "G" sensor system.
- shuts down fuel injection system if bike lies on its side for more than 10 seconds
- no special procedure to re-start the bike... just kick it and go
- helps prevent costly engine damage