Here's how to find it:
1. Locate the engine: The engine is the large, metal casing on the left side of the motorcycle when you're sitting on it.
2. Look for the oil fill cap: It's typically a round, black cap with a "fill" or "oil" symbol on it.
3. Find the oil fill cap on the right side: The oil fill cap will be on the right side of the engine, facing you.
Important:
* Use the correct type of oil: Refer to your Yamaha TTR 125 owner's manual for the recommended oil type and viscosity.
* Check the oil level regularly: Make sure the oil level is within the "full" and "low" markings on the dipstick.
* Change the oil regularly: Consult your owner's manual for the recommended oil change intervals.
Note: The specific location of the oil fill cap may vary slightly depending on the model year of your Yamaha TTR 125. If you're unsure, consult your owner's manual or contact a qualified motorcycle mechanic.