The Yamaha Grizzly 660, a popular ATV known for its reliability and power, requires regular maintenance, including valve lash adjustment. Ignoring this crucial step can lead to decreased engine performance, reduced fuel efficiency, and even engine damage. This guide provides a comprehensive walkthrough of the valve lash adjustment procedure for the 2003 Yamaha Grizzly 660, and applies generally to the 2000-2008 model years. While specific details might vary slightly depending on the exact year, the core process remains consistent. Always refer to your owner's manual for the most precise specifications for your particular machine.
Understanding Valve Lash
Before diving into the adjustment process, it's essential to understand what valve lash is. Valve lash, also known as valve clearance, refers to the small gap between the valve stem and the rocker arm (or tappet). This gap is necessary to prevent the valves from staying open too long, leading to overheating and potential damage. Over time, this gap can change due to wear and tear on the valve components. An incorrect valve lash can lead to a variety of issues including:
- Poor engine performance: Reduced power and acceleration.
- Rough running: Engine misfires or inconsistent idling.
- Reduced fuel efficiency: Increased fuel consumption.
- Valve damage: Burnt valves or premature wear.
Tools and Materials Required
Before you begin, gather the necessary tools and materials:
- Yamaha Grizzly 660 service manual: This is crucial for precise specifications and detailed diagrams.
- Feeler gauges: A set of feeler gauges in various thicknesses is essential for accurate valve lash measurement.
- Socket wrench set: A comprehensive set will be needed to remove and reinstall various components.
- Torque wrench: To ensure proper tightening of bolts and nuts.
- Gloves and safety glasses: Always prioritize safety when working on any mechanical equipment.
- Clean rags: To keep the engine clean and prevent debris from entering.
- Drain pan: For collecting any spilled fluids.
How to Adjust Valve Lash on a 2003 Yamaha Grizzly 660
Note: The following steps provide a general overview. Consult your owner's manual for precise specifications and torque values for your specific model year. This task is best suited for someone with mechanical experience. If unsure about any step, it's best to seek assistance from a qualified mechanic.
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Prepare the ATV: Park the ATV on a level surface, engage the parking brake, and disconnect the negative terminal from the battery.
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Drain the coolant: Drain the engine coolant to prevent accidental spills during the adjustment process.
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Remove the cylinder head cover: Carefully remove the cylinder head cover to access the valves and rocker arms.
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Locate the valve adjustment points: Identify the intake and exhaust valves for each cylinder and their corresponding rocker arms.
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Verify Valve Lash: Using the appropriate feeler gauge thickness specified in your service manual (typically 0.004-0.008 inches for intake and 0.008-0.012 inches for exhaust, but this may vary significantly – consult your manual!), check the existing valve lash for each valve.
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Adjust the valve lash: If the valve lash is incorrect, adjust it using the adjusting screws on the rocker arms. Tighten the adjusting screw until the feeler gauge just fits snugly between the valve stem and rocker arm. Then, tighten the lock nut to secure the adjustment.
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Repeat for all valves: Repeat steps 5 and 6 for all intake and exhaust valves.
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Reassemble the cylinder head cover: Carefully reassemble the cylinder head cover, ensuring a proper seal.
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Refill the coolant: Refill the engine coolant to the appropriate level.
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Test the ATV: Start the ATV and allow it to run for a few minutes to verify the valve lash adjustment. Listen for any unusual noises or inconsistencies in the engine's operation.
Frequently Asked Questions
What are the symptoms of incorrect valve lash?
Symptoms of incorrect valve lash include rough running, poor engine performance, decreased fuel efficiency, and potentially loud ticking noises from the engine. These symptoms can vary in severity depending on the extent of the misadjustment.
How often should I adjust the valve lash on my Yamaha Grizzly 660?
The recommended valve lash adjustment interval for the Yamaha Grizzly 660 is typically every 10,000 miles or one year, whichever comes first. However, this can vary based on usage and conditions. Consult your owner's manual for the recommended schedule.
Can I adjust the valve lash myself?
While it's possible to adjust the valve lash yourself, it requires mechanical knowledge and the correct tools. If you're not comfortable performing this task, it's best to seek assistance from a qualified mechanic. Incorrect adjustment can cause serious engine damage.
What happens if I don't adjust the valve lash?
Neglecting valve lash adjustment can lead to decreased engine performance, reduced fuel efficiency, valve damage, and even catastrophic engine failure. Regular maintenance, including valve lash checks, is crucial for maintaining the lifespan and optimal performance of your ATV.
This guide provides a general overview and should be supplemented with your specific year's service manual for precise details and specifications. Remember, safety is paramount – if you are unsure about any step, consult a qualified mechanic.
