How to Change the Oil in a 1999 Yamaha Yz400fby Chris Gilliland; Updated November 07, 2017
Items you will need
Oil catch pan
10 and 17 mm sockets
4 and 5 mm Allen wrenches
2 quarts, 10W-30 Type SH engine oil
The 1998 YZ400F was Yamaha's first four-stroke entry into the highly competitive motocross dirt bike category. Although the motocross scene had been dominated entirely by two-stroke machines up to this point, the YZ400F proved to be a championship-winning motorcycle that same year. The 1999 YZ400F remained unchanged from the previous year as a testament to its race-worthiness. However, the demands of off-road racing placed an emphasis on maintenance and required an oil change every five hours of use.
Start your YZ400F and take it for a short, five-minute ride to warm the engine oil. Place the YZ400F on its triangular stand once it has warmed and let it cool for 10 minutes.
Place an oil catch pan below the YZ400F's engine. Unscrew the engine crankcase drain plug, located at the center of the skid plate beneath the engine, using a socket wrench and a 17 mm socket. Let the crankcase oil drain until it diminishes to a light trickle.
Unscrew the oil tank cap from the YZ400F's frame, between the fuel tank and the handlebars. Place a funnel below the oil tank drain plug, located on the bottom of the forward frame rail near the front of the engine. Point the funnel at your oil catch pan, then unscrew the oil tank drain plug, using a socket wrench and a 14 mm socket. Let the oil drain from the oil tank until it diminishes to a light trickle.
Clean the crankcase and oil tank drain plug tips and threads with a shop towel, then screw the plugs into the engine and the frame by hand. Tighten the crankcase drain plug to 14 foot-pounds, using a torque wrench and a 17 mm socket. Tighten the oil tank drain plug to 17 foot-pounds, using a torque wrench and a 14 mm socket.
Loosen the clamp attaching the exhaust pipe to the muffler, using a flat screwdriver. Unscrew the exhaust pipe bolts from the front of the engine cylinder, using a 5 mm Allen wrench. Pull the exhaust pipe forward by hand until it separates from the engine cylinder and the muffler.
Unscrew the lower oil filter cover bolt, located at the front of the right engine crankcase cover, using a 4 mm Allen wrench. Let the oil remaining in the oil filter housing drain into your oil catch pan. Unscrew the two upper oil filter cover bolts, using a socket wrench and a 10 mm socket. Pull the oil filter cover and the oil filer out of the right side of engine.
Push a new oil filter into the oil filter housing by hand. Check the O-rings on the inner face of the oil filter cover for tears or brittleness. Remove and replace the O-rings, if they are damaged in any way. Coat the O-rings with a 10W-30 Type SH engine oil, then push the oil filter cover into place. Tighten the oil filter cover bolts to 7.2 foot-pounds, using a torque wrench, 4 mm Allen socket and 10 mm socket.
Slip the exhaust pipe into the muffler and the exhaust port at the front of the engine cylinder by hand. Screw the exhaust pipe bolts into place, using a 5 mm Allen wrench. Tighten the bolts to 17 foot-pounds, using a torque wrench and a 5 mm Allen socket. Tighten the muffler clamp, using a flat screwdriver.
Place a funnel into the oil tank filler neck. Fill the oil tank with 1.5 quarts of 10W-30 engine oil. Remove the funnel and screw the oil cap into place by hand.
Wipe away any spilled oil with a shop towel, then start the YZ400F's engine to circulate the oil. Let the motorcycle idle for three minutes, then stop the engine. Remove the oil cap and clean its dipstick with a shop towel. Reinsert the dipstick into the oil tank, then withdraw it. Add one to 2 ounces of oil into the oil tank at a time, if the oil level is below the lower mark imprinted on the dipstick. Clean the dipstick and screw the oil cap into place, if the oil level is between the dipstick's upper and lower marks.
Let the YZ400F cool slightly before beginning the job. The engine, engine oil and exhaust pipe can be hot enough to cause serious burns. Store the used engine oil in a sealed container to prevent accidental spills or exposure to children and animals, if you cannot take to an oil recycling center immediately after finishing the oil change.