CONQUER DIRT The fuel injected YZ250F offers excellent power and amazing cornering performance thanks to exhaustive mass centralization efforts and a compact, super responsive chassis design. At the 2017 YZ250F press test, numerous journalists were shocked by the wide spread of power the YZ250F produces, even from low rpms. The YZ250F has the response and depth of power that the competition can’t match. MASS CENTRALIZATION Yamaha’s innovative engine design with forward mounted fuel injection delivers class leading power & handling. The “reversed” engine design concentrates many of the motorcycle’s heaviest components; engine, fuel tank & exhaust system, towards the center of the motorcycle achieving excellent mass centralization and reduced gyroscopic effects for light, nimble, championship winning performance.
2018 Yamaha YZ250F Motocross Motorcycle - Photo Gallery, Video, Specs, Features, Offers, Inventory and more. Results 1 - 16 of 364 - 18 June, 2018. FILE - FREE05 YAMAHA YZ250F MANUAL. Document Filetype: PDF 444.59 KB. 18 June, 2018 - Free05. Whether you are winsome validating the ebook 2018 Yamaha Yz250f Manual. Yamaha in pdf upcoming, in that apparatus you retiring onto the evenhanded site.
2018 Yamaha Yz250f Service Manual
Forward thinking With a winning track record that includes hard-fought FIM and AMA Championship wins on both sides of the Atlantic, the game-changing YZ250F has the right stuff to power you to the top of the podium. This high-tech motocross bike comes with a high-performance reverse cylinder head that gives you the winning advantage against the opposition. And with its refined aluminium frame and sharp suspension settings, you can run harder and faster from the gate to the flag! Whether you’re an experienced pro racer or a hard-charging amateur, the revolutionary YZ250F delivers all the power and agility that you need to maximise your potential. Think forward. Think YZ250F. ENGINE.
Design goals for the fuel injected YZ250F are a balance of easy cornering & a lightweight feeling. Thanks to excellent mass centralization. The fuel injected engine features a wide, controllable power band that sets the standard in the 250 class. “Reversed” liquid-cooled, 250cc, DOHC, 4-valve (titanium), single with fuel injection. excellent “ride ability & 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. “Reversed” engine design (FI system is front mounted, exhaust exits from rear of cylinder).
FI throttle body & air box are front mounted, providing a straight 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 & increases power). design also helps centralize mass for light, agile handling. 4-valve cylinder head features a 13.5:1 compression ratio.
4-valve design offers optimum flow & excellent power. compact combustion chamber provides optimum combustion speed while also reducing heat & power losses. Lightweight titanium valves. 31 mm titanium intake & 25 mm titanium exhaust valves with load reduced valve springs.
load reduced valve springs reduce internal power losses. titanium valves reduce weight & improve performance titanium valves are 40 to 45% lighter than steel valves. reduced valve weight improves valve train reliability & longevity. reduced reciprocating weight allows for a higher rpm limit & better control of the valves. Automatic cam chain tensioner. reduces maintenance & mechanical engine noise. special cam chain “sliders” reduce internal friction losses.
High lift intake & exhaust camshafts. strong power with excellent “control-ability”.
hollow design reduces weight. “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 & therefore reducing weight. excellent heat dissipation for consistent power delivery. coating enhances the thin film of oil between cylinder & piston, reducing friction & increasing power.
Cylinder “cutaways” allow air “trapped” under the piston to enter a special side chamber (cutaway). reduces horsepower-robbing “pumping losses”. Crankcase also utilizes special “cutaways.”. reduces horsepower-robbing “pumping losses”. crankcase cutaways match cylinder cutaways for maximum efficiency. Lightweight, short-skirt, forged aluminum piston.
flat top piston with lateral ribs on both sides of the piston pin area for strength & durability. single compression ring & specially designed oil control ring increases the surface contact area for better sealing. 2-ring design decreases sliding resistance, reduces weight & 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 & underside of piston. reduces piston, cylinder & rod temperatures for excellent durability.
Ball bearing style crankshaft. heat treated for strength & durability.
balance ratio of the crank has been optimized to reduce vibration. Nickel-chromium-molybdenum connecting rod. excellent strength & durability. molybdenum coated thrust washers on either side of the rod to reduce friction.
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Lightweight gear driven counter balancer shaft. reduces vibration for improved rider comfort & less rider fatigue.
5-speed transmission utilizes a 2-bar, floating shift guide system & 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. see spec page for gear ratios. Heavy duty, clutch with quick access magnesium outer cover & on the fly “barrel” adjuster. quick access, lightweight, magnesium outer cover provides fast & 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. 44mm Keihin throttle body fuel injection system. 10-hole injector maximizes fuel atomization for more complete combustion. FI benefits include automatic adjustments to insure the optimum fuel — air ratio regardless of outside air temperature & altitude. other benefits include excellent starting & instant throttle response.
cold start knob also doubles as an idle adjuster. Injector spray pattern, spray direction & distance to the intake valves have been optimized.
forward mounted straight intake tract maximizes benefits of the FI system & improves power output. Optional, compact, hand held “GYTR Power Tuner” allows tailoring of both fuel injection duration & ignition mapping.
9-different setting points can be accessed for both fuel injection duration & ignition maps. maps can be stored & shared with other Power Tuners if desired.
easy access GYTR Power Tuner connector port. Forward mounted air box features a washable, dual-stage, foam air filter. no tools required to access air filter. washable foam filter reduces tune up costs.
2018 Yamaha Yz250f
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 & weight. fast & easy oil changes.
Compact, lightweight, single core, dual radiators. provide excellent 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.
exhaust exits from the rear of the engine & 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. Lightweight, aluminum, re-packable muffler (aka silencer). sound output is 94 dB meeting CMRC & AMA regulations.
muffler / silencer is re-buildable for optimum performance & 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 & go. helps prevent costly engine damage.
CHASSIS/SUSPENSION. Compact “Bilateral Beam” aluminum frame. frame & engine designs centralize mass for exceptional handling & maneuverability. frame offers an optimum rigidity balance between strength, rigidity & tuned flex, plus excellent shock absorbing qualities. frame design provides excellent “rider — machine communication” (a.k.a. Feedback).
key goal of this chassis design is faster & easier cornering one of the keys to winning races. Lightweight, tapered aluminum swingarm. lightweight design reduces unsprung weight for excellent suspension performance. excellent rear wheel traction & control.
large 25 mm rear axle. Lightweight detachable rear sub frame. constructed of square-section, lightweight aluminum pipe with no bends. allows easy access when servicing rear suspension components. reduces costs in the event of damage. 48mm, adjustable, inverted, Kayaba “SSS” cartridge fork offers 310mm (12.2″) of wheel travel.