User manual YAMAHA WR250FN

[. . . ] Thank-you for downloading this manual from MYXmanuals. If you have a manual you think we should have, please drop us a line, and we will give it a home. You should own the original manual to be able to download this backup. Any reprinting or unauthorized use without the written permission of Yamaha Motor Co. [. . . ] Scalding hot fluid and steam may be blown out under pressure, which could cause serious injury. When the engine has cooled, open the radiator cap by the following procedure: Place a thick rag, like a towel, over the radiator cap, slowly rotate the cap counterclockwise to the detent. This procedure allows any residual pressure to escape. When the hissing sound has stopped, press down on the cap while turning counterclockwise and remove it. Inspect: q Radiator core 1 Obstruction Blow out with compressed air through rear of the radiator. 1 Carburetor removal Part name CARBURETOR REMOVAL Seat and fuel tank Clamp Throttle position sensor lead coupler Throttle cable cover Throttle cable Throttle cable cap Clamp (air filter joint) Clamp (carburetor joint) Carburetor assembly Carburetor joint 2 1 1 2 1 1 2 1 1 Q'ty Remarks Refer to "SEAT, FUEL TANK AND SIDE COVERS" section. 1 Carburetor disassembly Part name CARBURETOR DISASSEMBLY Carburetor breather hose Valve lever housing cover Screw (throttle shaft) Throttle valve Needle holder Jet needle Accelerator pump cover Spring Diaphragm (accelerator pump) Air cut valve cover Spring (air cut valve) Diaphragm (air cut valve) Float chamber Leak jet Pilot screw Float pin Q'ty 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Remarks Pull the push rod. Do not loosen the screws (throttle position sensor) 1 except when changing the throttle position sensor due to failure because it will cause a drop in engine performance. Remove: q Pilot screw 1 NOTE: To optimize the fuel flow at a small throttle opening, each machine's pilot screw has been individually set at the factory. Before removing the pilot screw, turn it in fully and count the number of turns. Record this number as the factory-set number of turns out. Blow out all passages and jets with compressed air. Blow out all passages and jets with compressed air. Inspect: q Needle valve 1 q Valve seat 2 Grooved wear a Replace. NOTE: Insert the throttle valve 1 into the carburetor body, and check for free movement. NOTE: q Slowly tilt the carburetor in the opposite direction, then take the measurement when the needle valve aligns with the float arm. Q If the carburetor is level, the weight of the float will push in the needle valve, resulting in an incorrect measurement. Measure the distance between the mating surface of the float chamber and top of the float using a vernier calipers. NOTE: The float arm should be resting on the needle valve, but not compressing the needle valve. If the float height is not within specification, inspect the valve seat and needle valve. Inspect: q Diaphragm (air cut valve) 1 q Spring (air cut valve) 2 q Air cut valve cover 3 q O-ring 4 Tears (diaphragm)/damage Replace. Install: q Washer 1 q Circlip 2 NOTE: Make sure the stopper a of the spring 2 fits into the recess b in the carburetor. [. . . ] Remove the stand or block from the engine and with a rider astride the seat, measure the sunken length b between the rear wheel axle center and the rear fender holding bolt. Loosen the locknut 1 and make adjustment by turning the spring adjuster 2 to achieve the standard figure from the subtraction of the length b from the length a. NOTE: q If the machine is new and after it is broken in, the same set length of the spring may change because of the initial fatigue, etc. Therefore, be sure to make reevaluation. [. . . ]