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   Summary of Contents for Yamaha wr250f

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    INSP THROTTLE CABLE ADJUSTMENT THROTTLE CABLE ADJUSTMENT 1. Check: Throttle grip free play a Out of specification → Adjust. Throttle grip free play a: 3 ~ 5 mm (0.12 ~ 0.20 in) 2. Adjust: Throttle grip free play Throttle grip free play adjustment steps: Remove the throttle cable cap 1 and throttle cable cover 2.

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    THROTTLE LUBRICATION/ INSP DECOMPRESSION ADJUSTMENT THROTTLE LUBRICATION 1. Remove: Rubber cover 1 Throttle grip cap 2 2. Apply: Lithium soap base grease On the throttle cable end a. 3. Install: Throttle grip cap Screw (throttle grip cap) 4 Nm (0.4 m · kg, 2.9 ft · lb) Rubber cover DECOMPRESSION ADJUSTMENT 1.

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    ENGINE IDLING SPEED ADJUSTMENT/ INSP VALVE CLEARANCE INSPECTION AND ADJUSTMENT ENGINE IDLING SPEED ADJUSTMENT 1. Start the engine and thoroughly warm it 2. Attach: Inductive tachometer To spark plug lead. 3. Adjust: Engine idling speed Adjustment steps: Adjust the pilot screw. Refer to “PILOT SCREW ADJUSTMENT”...

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    CARBURETOR CARBURETOR Extent of removal: 1 Carburetor removal Extent of removal Order Part name Q’ty Remarks CARBURETOR REMOVAL Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE COVERS” section. Clamp Throttle position sensor lead cou- pler Throttle cable cover Throttle cable...

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    CARBURETOR EC468000 CARBURETOR DISASSEMBLY Extent of removal: 1 Carburetor disassembly Extent of removal Order Part name Q’ty Remarks 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)

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    CARBURETOR Extent of removal Order Part name Q’ty Remarks Float Needle valve Valve seat Main jet Needle jet Spacer Pilot jet Starter jet Push rod Pull the push rod. Throttle shaft assembly Push rod link lever assembly Intake joint Pilot air jet Main air jet Cold starter plunger Hot starter plunger (red)

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    CARBURETOR HANDLING NOTE CAUTION: Do not loosen the screws (throttle position sensor) 1 except when changing the throt- tle position sensor due to failure because it will cause a drop in engine performance. REMOVAL POINTS Pilot screw 1. Remove: Pilot screw 1 NOTE: To optimize the fuel flow at a small throttle opening, each machine’s pilot screw has been...

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    CARBURETOR 2. Inspect: Main jet 1 Pilot jet 2 Needle jet 3 Starter jet 4 Main air jet 5 Pilot air jet 6 Leak jet 7 Damage → Replace. Contamination → Clean. NOTE: Use a petroleum based solvent for cleaning. Blow out all passages and jets with com- pressed air.

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    CARBURETOR Float height 1. Measure: Float height a Out of specification → Adjust. Float height: 8.0 mm (0.31 in) Measurement and adjustment steps: Hold the carburetor in an upside down position. NOTE: Slowly tilt the carburetor in the opposite direction, then take the measurement when the needle valve aligns with the float arm.

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    CARBURETOR Starter plunger 1. Inspect: Cold starter plunger 1 Hot starter plunger (red) 2 Wear/damage → Replace. Accelerator pump 1. Inspect: Diaphragm (accelerator pump) 1 Spring (accelerator pump) 2 Accelerator pump cover 3 O-ring 4 Push rod 5 Tears (diaphragm)/damage → Replace. Dirt →...

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    CARBURETOR 2. Install: Main air jet 1 Pilot air jet 2 Intake joint 3 5 Nm (0.5 m · kg, 3.6 ft · lb) 3. Install: Spring 1 1 Lever 1 2 To lever 2 3. NOTE: Make sure the spring 1 fits on the stopper a of the lever 2.

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    CARBURETOR 7. Install: Spring 1 Joint collar 2 To throttle shaft 3. NOTE: Install the bigger hook a of the spring fits on the stopper b of the throttle shaft pulley. 8. Install: Throttle shaft assembly 1 Washer (metal) 2 Washer (resin) 3 Valve lever 4 NOTE:...

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    CARBURETOR 10. Install: Starter jet 1 Pilot jet 2 Spacer 3 Needle jet 4 Main jet 5 11. Install: Valve seat Screw (valve seat) 1 Needle valve 2 Float 3 Float pin 4 NOTE: After installing the needle valve to the float, install them to the carburetor.

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    CARBURETOR 14. Install: Diaphragm (air cut valve) 1 Spring (air cut valve) 2 O-ring 3 Air cut valve cover 4 Screw (air cut valve cover) 5 15. Install: Diaphragm (accelerator pump) 1 Spring 2 O-ring 3 Accelerator pump cover 4 Bolt (accelerator pump cover) 5 NOTE: Install the diaphragm (accelerator pump) with...

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    CARBURETOR 19. Install: Carburetor breather hose 1 NOTE: Install the carburetor breather hoses to the carburetor so that the hoses do not bend near where they are installed. Carburetor installation 1. Install: Clamp 1 NOTE: Install the projections a on the carburetor joint between the clamp ends.

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    CARBURETOR 5. Install: Throttle cable cap 1 6. Install: Throttle cable 1 7. Adjust: Throttle grip free play Refer to “THROTTLE CABLE ADJUST- MENT” section in the CHAPTER 3. 8. Install: Throttle cable cover 1 Screw (throttle cable cover) 2 4 Nm (0.4 m ·...

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    – ELEC THROTTLE POSITION SENSOR SYSTEM THROTTLE POSITION SENSOR SYSTEM INSPECTION STEPS If the throttle position sensor will not operate, use the following inspection steps. No good Check entire ignition Repair or replace. system for connection. No good Check throttle position Throttle posi- Replace.

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    – ELEC THROTTLE POSITION SENSOR SYSTEM EC624000 COUPLERS AND LEADS CONNECTION INSPECTION 1. Check: Couplers and leads connection Rust/dust/looseness/short-circuit → Repair or replace. THROTTLE POSITION SENSOR COIL INSPECTION 1. Inspect: Throttle position sensor coil resistance Out of specification → Replace. Tester (+) lead →...

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    – ELEC THROTTLE POSITION SENSOR SYSTEM THROTTLE POSITION SENSOR REPLACEMENT AND ADJUSTMENT 1. Remove: Throttle position sensor coupler Screw (throttle position sensor) 1 Washer 2 Throttle position sensor 3 NOTE: Loosen the screws (throttle position sensor) using the T20 bit (tamper resistant fastener type).

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    – ELEC THROTTLE POSITION SENSOR SYSTEM 6. Adjust: Throttle position sensor coil resistance at idle speed Adjustment steps: Adjust the angle of the throttle position sen- sor 1 to obtain the resistance calculated (example: 650 ~ 750 Ω) Tester (+) lead → Yellow lead 2 Tester (–) lead →...

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    T U N SETTING EC700000 TUNING EC710000 ENGINE Carburetor setting The air/fuel mixture will vary depending on atmospheric conditions. Therefore, it is nec- essary to take into consideration the air pres- sure, ambient temperature, humidity, etc., when adjusting the carburetor. Perform a test run to check for proper engine performance (e.g., throttle response) and spark plug(-s) discoloration or fouling.

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    T U N SETTING CAUTION: The carburetor is extremely sensitive to foreign matter (dirt, sand, water, etc.). During installation, do not allow foreign matter to get into the carburetor. Always handle the carburetor and its components carefully. Even slight scratches, bends or damage to carbure- tor parts may prevent the carburetor from functioning correctly.

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    T U N SETTING Effects of the setting parts on the throttle valve opening ı Å Å ı Å Closed ı Fully open 1 Pilot screw/pilot jet 2 Throttle valve cutaway 3 Jet needle 4 Main jet Main system The FLATCR carburetor has a primary main jet.

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    T U N SETTING 1 Jet needle 2 Main air jet 3 Pilot air jet 4 Needle jet 5 Main jet 6 Pilot jet 7 Pilot screw Main jet adjustment The richness of the air-fuel mixture at full throt- tle can be set by changing the main jet 1 . Standard main jet #170 If the air-fuel mixture is too rich or too lean, the...

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    T U N SETTING Pilot screw adjustment The richness of the air-fuel mixture with the throttle fully closed to 1/4 open can be set by turning the pilot screw 1 . Turning in the pilot screw will make the mixture lean at low speeds, and turning it out will enrich it.

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    T U N SETTING Effects of adjusting the pilot jet (reference) Å ı –5% Å Idle ı Fully open Jet needle groove position adjustment Adjusting the jet needle 1 position affects the acceleration when the throttle is 1/8 to 3/4 open.

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    T U N SETTING Jet needle adjustment The jet needle is adjusted by changing it. OBELP Standard jet needle *OBEGP **OBEHP * For EUROPE ** For CDN, ZA, AUS and NZ The tapered sections of all jet needles have the same starting positions, but the needles are available with different straight-portion diameters.

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    T U N SETTING Effects of changing the jet needle (reference) (Diameter of the straight portion) Changing the diameter of the straight portion adjusts the air-fuel mixture when the throttle is 1/8 to 1/4 open. Å ı +10 % –10 % Å...

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    T U N SETTING EC71Q000 Carburetor setting parts Part name Size Part number Main jet Rich #185 4MX-14943-44 #182 4MX-14943-94 #180 4MX-14943-43 #178 4MX-14943-93 #175 4MX-14943-42 #172 4MX-14943-92 (STD) #170 4MX-14943-41 #168 4MX-14943-91 #165 4MX-14943-40 #162 4MX-14943-90 Lean #160 4MX-14943-39 Pilot jet Rich 4MX-14948-07...

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    T U N SETTING Examples of carburetor setting depending on symptom Symptom Setting Checking Discoloration of spark plug → At full throttle Increase main jet calibration no. Hard breathing (Gradually) If tan color, it is in good condition. Shearing noise If cannot be corrected: Whitish spark plug Clogged float valve seat...

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