Qlink RD400 User Manual page 111

To change the engine oil (with or without oil filter cartridge
replacement).
1. Start the engine, warm it up for several minutes, and
then turn it off.
2. Place an oil pan under the engine to collect the used oil,
and then remove the engine oil filler cap.
3. Remove the engine oil drain bolt to drain the oil from
the crankcase.
① Engine oil drain bolt
USER'S MANUAL
NOTE:
Skip steps 4-6 if the oil filter cartridge is not being replaced.
4. Remove the oil filter cartridge with an oil filter wrench.
105
① Oil filter cartridge