The Yamaha Grizzly 660, a popular ATV known for its reliability and power, requires regular maintenance to ensure optimal performance. One crucial aspect of this maintenance is valve lash adjustment. Ignoring this can lead to decreased engine efficiency, poor fuel economy, and ultimately, engine damage. This guide will walk you through the process of checking and adjusting valve lash on your 2003 (and similar years, 2000-2008) Yamaha Grizzly 660.
Understanding Valve Lash
Valve lash, also known as valve clearance, is the small gap between the valve stem and the rocker arm (or tappet) when the valve is closed. This gap is essential for proper valve operation. Too much clearance (loose lash) can lead to noisy operation and incomplete valve closure, while too little clearance (tight lash) can restrict valve movement, causing the valve to burn or even break.
Tools and Materials You'll Need
Before you begin, gather the necessary tools and materials. This will make the process much smoother and more efficient. You'll need:
- Yamaha Grizzly 660 Service Manual: This is crucial for accurate specifications and diagrams.
- Feeler Gauges: A set of feeler gauges with the correct thicknesses specified in your service manual.
- Socket Wrench Set: To remove and replace the valve cover and other components.
- Torque Wrench: To tighten bolts to the manufacturer's specifications, preventing damage.
- Clean Rags: To keep the engine clean and prevent debris from entering.
- Gloves: For protection and cleanliness.
- Drain Pan: To collect any spilled oil.
How to Check and Adjust Valve Lash on a Yamaha Grizzly 660
This procedure requires precision and patience. Refer to your service manual for specific torque values and valve clearance specifications. The following steps provide a general overview:
1. Preparation:
- Safety First: Disconnect the battery negative terminal before starting any work on the engine.
- Warm-up the Engine: Run the engine until it reaches operating temperature. This helps ensure accurate readings.
- Drain Some Oil: Drain a small amount of engine oil to prevent spills during the valve cover removal.
2. Accessing the Valves:
- Remove the Valve Cover: Locate and carefully remove the valve cover bolts, taking note of their positions for reassembly.
- Clean the Area: Clean any dirt or debris around the valve train to prevent it from getting into the engine.
3. Measuring Valve Lash:
- Identify the Valves: Locate the intake and exhaust valves. Your service manual will clearly show the location.
- Use Feeler Gauges: Using the correct feeler gauge thickness (as specified in your service manual), check the clearance between the valve stem and the rocker arm for each valve. The feeler gauge should slide smoothly but with slight resistance.
4. Adjusting Valve Lash (if necessary):
- Adjusting Screws: Your Yamaha Grizzly 660 likely uses shims to adjust valve lash. You'll need to remove the rocker arm and replace the shim with one of a different thickness to achieve the correct clearance. This process is detailed in your service manual. Do not attempt to adjust the valves without referring to your service manual.
5. Reassembly:
- Replace Shims: Once you’ve chosen the appropriate shims, carefully reassemble the rocker arms and valve cover.
- Torque Specifications: Tighten all bolts to the manufacturer’s specifications using a torque wrench.
- Check Oil Level: Check and refill the engine oil to the correct level.
6. Post-Adjustment Check:
- Restart the Engine: Start the engine and listen for any unusual noises. If you hear any ticking or clicking, you may need to recheck and readjust the valve lash.
Frequently Asked Questions (FAQs)
How often should I check my Grizzly 660's valve lash?
The recommended interval for checking valve lash is typically every 6,000-10,000 miles or according to your Yamaha Grizzly 660's service manual. It's a preventative maintenance step that can save you from more costly repairs in the long run.
What happens if I don't adjust my valve lash?
Neglecting valve lash adjustment can lead to a variety of problems, including reduced engine performance, poor fuel economy, and ultimately, engine damage. This is due to either incomplete valve closure or restricted valve movement.
Can I adjust the valve lash myself?
While you can attempt to adjust the valve lash yourself, it's recommended to consult your Yamaha Grizzly 660 service manual and potentially seek assistance from a qualified mechanic if you're not comfortable with engine repair. Improper adjustment can cause serious engine damage.
What are the signs of incorrect valve lash?
Signs of incorrect valve lash can include engine noise (ticking, clicking), reduced power, poor fuel economy, and misfires.
This guide provides a general overview. Always refer to your Yamaha Grizzly 660 service manual for specific instructions, torque values, and valve clearance specifications. Safety should always be your top priority when performing any engine maintenance.
