1999-2004 Honda TRX400EX FourTrax Service Manual, Page 44Get this manual
MAINTENANCE A Crankcase Oil Check Bolt
NOTE The crankcase oil level check bolt is useful when checking the lubrication; the oil pump adjusts the oil level so that the crankcase is always kept at the proper levelIf this check shows otherwise, some portion of the lubrication system is not working properly Do not check the oil level immediately after the engine has been operated at high speedsMake sure that vehicle is on firm level ground while idlingAllow the engine to idle for few minutes to stabilize the oil levels
OIL CHECK BOLT AND SEALING WASHER
The crankcase oil level is correct if the oil is flush with the bottom of the check bolt hole
OIL CHANGE
CAUTION: Used engine oil may cause skin cancer if repeatedly left in contact with the skin for prolonged periodsAlthough this is unlikely unless you handle used oil on daily basis, it is still advisable to thoroughly wash your hands with soap and water as soon aspossible after handling used oilNOTE: Change the oil with the engine warm to assure comDlete and raDid draininoStart the engine and let it idle for few minutesStop the engine and remove the oil filler capldipstickRemove the oil tank and crankcase drain bolts with the sealing washers and drain the engine oilAfter the oil has drained, install the drain bolts with new sealing washers