How to Change the Oil in a 1986 Yamaha YZ125

Shop parts for a 1986 Yamaha YZ125 Dirt Bike.

Changing the oil in a 1986 Yamaha YZ125 is a straightforward process that requires some basic tools and knowledge. Here's a step-by-step guide to help you through the process. ### Tools Needed: - Drain Pan - 12mm Socket or Wrench (for the drain bolt) - Funnel (long enough to reach under the exhaust system) - Rag - New Oil Filter (if applicable, though not all models have one) - Oil for 2-Stroke Engine (e.g., Yamalube 2-R or equivalent with a mixing ratio, though 2-strokes primarily use premix oil) - 2-Stroke Oil Mixing Cup - Gasoline (for premixing if necessary) ### Steps to Change the Oil: 1. Warm Up the Engine: Start the engine and let it run for a few minutes to warm up the oil. This will help it drain more easily. 2. Position the Bike: Ensure the bike is on level ground to prevent oil spills and for safe working conditions. 3. Remove the Drain Bolt: - Use a 12mm socket or wrench to remove the drain bolt located at the bottom of the crankcase. - Be prepared for the oil to start draining out. Place a drain pan underneath to catch the oil. 4. Drain the Oil: - Allow all the old oil to drain into the pan. If the bike uses a transmission/gear oil (unlikely for a 2-stroke), you might need to follow specific procedures for that as well. 5. Replace the Drain Bolt: - Once the oil has stopped dripping, replace the drain bolt and tighten it securely. Make sure to use a new drain bolt washer if the old one is damaged. 6. Add New Oil (Pre-mix for 2-Stroke): - For a 2-stroke engine like the YZ125, you typically mix oil with gasoline rather than adding it to a separate oil reservoir. Use a mixing ratio recommended by Yamaha, such as 30:1 or 15:1, depending on the specific oil and conditions. - Mix the correct amount of oil with gasoline in a separate container before adding it to the fuel tank. 7. Dispose of Used Oil: - Take the used oil to a recycling center or an auto parts store that accepts used oil for proper disposal. 8. Check for Leaks: - After replacing the drain bolt, start the engine and check for any leaks around the drain bolt area. ### Specific Call-Outs for the 1986 Yamaha YZ125: - Engine Type: The 1986 YZ125 is a 2-stroke engine, so it does not have a separate oil reservoir. Oil is mixed with gasoline in the fuel tank. - Maintenance: Regularly check the float bowl and adjust the carburetor as needed to ensure proper running. - Break-In Period: If new parts are installed, ensure they are properly broken in according to Yamaha–s guidelines. By following these steps, you'll be able to keep your 1986 Yamaha YZ125 in top condition, ensuring it runs smoothly and efficiently. Always refer to the service manual for specific torque values and other detailed instructions if needed.

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Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.