To change the motor oil of the Honda CRF 450 RL, start by warming up the engine for a few minutes to ensure that the oil is warm and fluid. Then, turn off the engine and lift the bike on a central stand for greater stability. Locate the oil drain plug on the bottom of the engine and place a suitable container underneath it to collect the used oil. Use a suitable wrench to unscrew the drain plug and let the oil drain completely into the container. Make sure the used oil is disposed of in an environmentally friendly and responsible manner. Once all the oil has drained, securely screw back the drain plug. Next, find and remove the oil fill cap located on the top of the engine. Use a clean funnel to pour the correct amount of new motor oil, as indicated in the motorcycle's user manual. Periodically check the oil level using the sight glass on the engine, making sure not to exceed the maximum level. After pouring the necessary oil, securely screw back the fill cap. Start the engine for a few minutes and check the oil level again after the engine has cooled slightly. Make sure there are no oil leaks and that the level is correct. Finally, clean any oil splashes and close the engine compartment.