1. Preparation:
- Allow the engine to cool down completely before starting any work.
- Gather the necessary tools, including a spark plug wrench, a flat-head screwdriver, a feeler gauge, and an adjustable wrench.
- Remove the seat, fuel tank, and airbox to access the valve cover.
2. Accessing the Valves:
- Locate the valve cover and remove the bolts holding it in place.
- Carefully remove the valve cover, being mindful of the valve cover gasket underneath.
3. Checking Valve Clearances:
- Locate the camshaft and the valves it actuates.
- Select the appropriate feeler gauge blade based on the valve clearance specifications provided in your YFZ's service manual.
- Insert the feeler gauge between the cam lobe and the valve stem.
- There should be a slight drag when the feeler gauge is inserted. If the gauge moves too freely, the clearance is excessive, while if it is difficult to insert, the clearance is too tight.
4. Adjusting Valve Clearances:
- If any valve clearances are incorrect, adjustments need to be made.
- Use an adjustable wrench to loosen the locknut on the valve adjuster.
- Turn the adjuster screw either clockwise (to decrease clearance) or counterclockwise (to increase clearance) using a flat-head screwdriver until the desired clearance is achieved.
- Tighten the locknut to secure the adjustment.
5. Reassemble:
- Reinstall the valve cover, ensuring the gasket is properly seated.
- Reinstall the bolts and tighten them to the recommended torque specifications.
- Reinstall the airbox, fuel tank, and seat in the reverse order of removal.
It is important to follow the exact procedure outlined in the service manual for your specific YFZ model, as there may be slight variations in the steps and specifications. If you are not comfortable performing this procedure, it is best to consult with a qualified mechanic.
