Engine -
Latest-gen "reversed" liquid-cooled, 250 cc, DOHC, 4-valve (titanium), single-cylinder engine with fuel injection. The engine has been tuned specifically for XC/woods racing with a broad, easy-to-use powerband and excellent power characteristics throughout the rev range.
-
Rearward-slanted, reversed cylinder design.
- rearward slant moves a significant amount of rotating weight toward the centre of the chassis
- rearward-slanted cylinder centralizes mass for excellent handling and a light, agile feel
-
"Reversed" engine design (FI system is front-mounted, exhaust exits from rear of cylinder).
- forward-mounted FI provides straight intake path into the cylinder and provides optimum fuel/ air filling and flow for excellent power
- front-mounted intake design 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
-
Electric start with auto decompression system (no kick starter). Unit can be re-started in any gear.
- there is no main ignition switch on this model
- electric start button (RHS handlebar) activates the entire electrical system
- kill switch (LHS handlebar), if held for a few seconds, shuts down entire electrical system
-
Lightweight titanium valves and optimized valve springs.
- titanium valves reduce reciprocating weight and allow for a higher rpm limit before valve float
- titanium valves means a fast-revving engine with smooth power delivery
- 31 mm titanium intake valves and 25 mm titanium exhaust valves
-
Automatic cam chain tensioner.
- reduces maintenance
- special cam chain "sliders" reduce internal friction losses
-
Lightweight, short-skirt, forged aluminum piston.
- light flat-top piston features lateral ribs on both sides of the piston pin area
- single compression ring and specially designed oil control ring increases surface contact area for optimal sealing
- 2-ring design decreases sliding resistance, reduces weight and provides faster throttle response
-
Lightweight piston pin features a diamond-like coating (DLC) to reduce 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
-
"Liner-less" lightweight aluminum cylinder with ceramic composite coating.
- ceramic coating sprayed directly on the aluminum block, eliminating the need for a liner and 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 and crankcase "cutaways" allow air "trapped" under the piston to enter special chambers or cutaways.
- reduces horsepower-robbing "pumping losses"
- crankcase cutaways match cylinder cutaways for maximum efficiency
-
Ball-bearing-style crankshaft.
- bronze thrust washers located between crank webs and rod
- heat-treated for strength and durability
- balance ratio of the crank is optimized for minimal vibration and good torque feeling
-
Nickel-chromium-molybdenum connecting rod.
- excellent strength and durability
-
Lightweight, gear-driven counter balancer shaft.
- reduces vibration for improved rider comfort and less rider fatigue
-
6-speed transmission utilizes a 2-bar, floating shift guide system and a 14 mm shift shaft.
-
Heavy-duty, multi-plate clutch features a quick access magnesium outer cover.
- low-friction bushing on actuation arm reduces lever pull effort
- clutch is designed for the rigours of cross-country
- outer cover provides fast and easy clutch access
-
44mm Keihin throttle body fuel injection system.
- 10-hole injector
- maximizes fuel atomization for optimal combustion and excellent power delivery
- 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 excellent throttle response
- cold start knob also doubles as an idle adjuster
-
Handlebar-mounted engine trouble and low fuel warning lights.
-
Optional, GYTR competition ECU and GYTR Communication Control Unit (CCU) kit.
- Allows tailoring of both fuel injection and ignition mapping when used with Yamaha's free, exclusive Power Tuner app
- Monitor real-time data, track engine run time and run engine diagnostics
- Accurately log race data for future reference
- Share maps with friends and teammates
- Closed-course competition use only. Not for trail use
-
Forward-mounted air box features a washable, dual-stage, foam air filter.
- airbox cover features flush mounted quick release fasteners
- no tools required to access air filter
- washable foam filter reduces tune up costs
-
Wet sump lubrication system.
- reduces weight (no remote oil tank or oil lines)
- eases maintenance (easier and faster oil changes)
- oil volume is optimized to reduce oil related drag and weight
-
Easy access "cartridge-type" oil filter.
-
High-capacity radiator.
- large YZ250F-derived radiator features a cooling fan for consistent performance
- outstanding cooling efficiency
-
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
-
High-capacity AC magneto eliminates need for a battery.
-
Wrap-around exhaust system to match head, cam and intake.
- exhaust exits from the rear of the engine and circles cylinder body
- wrap-around design ensures the optimum tuned header length
- maximizes exhaust "pulse effect" for excellent power delivery
- centralizes mass by moving weight closer to the centre of the chassis
-
Lightweight, aluminum, re-packable muffler (aka silencer).
- sound output is 94 dB meeting AMA regulations
-
Works-style, race-spec "barrel adjuster" for on-the-fly clutch lever free play adjustments.
-
Heavy-duty plastic engine skid plate
-
Excessive lean angle sensor
- Will shut down the engine if the bike lays on its side
- helps prevent costly engine damage
|
RACE-READY PERFORMANCE
REFINED CHASSIS
