Where do you fill the oil in Yamaha 660?

To fill the oil in a Yamaha 660, locate the oil filler cap, which is typically found on the right side of the engine. Remove the cap and use a funnel to pour in the appropriate type and amount of engine oil, as specified in the owner's manual. After filling, replace the cap securely and check the oil level using the dipstick to ensure it's within the recommended range. Always make sure the bike is on a level surface while checking or filling the oil.