The likely causes of a slack timing chain on an XR500 are:
* Worn chain: The chain has stretched over time and needs replacement. This is the most common reason.
* Worn sprockets: The teeth on the crankshaft and camshaft sprockets can wear down, allowing the chain to become loose. This often accompanies a worn chain.
* Guide rails/tensioner issues: The guides that keep the chain aligned and a tensioner (if equipped) that helps maintain chain tension might be worn, broken, or malfunctioning.
What to do if your XR500's timing chain is slack:
1. Don't try to adjust it. There's no adjustment mechanism. Attempting to force it tighter could damage the engine.
2. Diagnose the problem: The chain is likely worn, but you should carefully inspect the sprockets and guides as well. This requires removing the valve cover and possibly the timing chain cover to thoroughly assess the condition of all components.
3. Replace worn parts: If the chain, sprockets, or guides are worn, they all need to be replaced as a set. Using a worn sprocket with a new chain will quickly wear out the new chain.
4. Check the tensioner (if applicable): Some engines have an automatic tensioner. If yours does, check its operation. A faulty tensioner might need repair or replacement.
5. Consult a service manual: A factory service manual specific to your XR500 is essential for proper disassembly, inspection, replacement of parts, and reassembly. Improper reassembly can cause serious engine damage.
Replacing a timing chain is a significant job, requiring mechanical knowledge and specialized tools. If you're not comfortable performing this level of maintenance, take your XR500 to a qualified motorcycle mechanic. A poorly repaired timing chain can lead to valve damage and other costly repairs.
