How to Change the Oil in a 1999 Yamaha YZ400F: A Complete Guide

Shop parts for a 1999 Yamaha YZ400F Dirt Bike.

Keeping your 1999 Yamaha YZ400F running at peak performance means sticking to a regular oil change schedule. The YZ400F, with its dry-sump lubrication system and multiple drain plugs, has some unique features and steps for oil changes that all owners should know. Follow this step-by-step guide for a successful oil change, and keep your ride running smooth.

Tools & Supplies Needed

  • Oil catch pan
  • Socket wrench set (14 mm, 17 mm, and 10 mm sockets)
  • 4 mm and 5 mm Allen wrenches
  • Torque wrench
  • Flathead screwdriver
  • Shop towels or cleaning cloths
  • Funnel
  • Replacement engine oil (refer to owner's manual for viscosity and amount, typically about 1.5 L of 10W-40 or 20W-50 four-stroke motorcycle oil)
  • Replacement oil filter
  • Replacement sealing washers/gaskets (recommended)

Step-by-Step Instructions

  • Warm Up the Engine:– Start your YZ400F and let it idle for about 5 minutes. This gets the oil warm so it flows out more easily and carries away more contaminants.
  • Place the Bike on Stand:– Put the bike securely on a triangular stand and let it cool for a few minutes so the oil isn't scalding. Make sure the bike is stable and upright.
  • Remove the Skid Plate:– For easier access to the drain bolts, remove the skid plate using a 10 mm or 12 mm socket (bolt size may vary due to previous replacements).
  • Drain the Oil from the Frame (Oil Tank):–
    • Locate the oil tank drain plug on the bottom of the forward frame rail near the front of the engine.
    • Place your oil catch pan and a funnel under this plug.
    • Using a 14 mm socket, unscrew the oil tank drain plug and let the oil drain until it's just a slow trickle.
  • Drain the Oil from the Crankcase:–
    • Locate the crankcase drain plug on the bottom of the right side of the engine.
    • Use a 17 mm socket to remove the crankcase drain plug and allow oil to drain completely.
  • Clean and Replace Drain Plugs:–
    • Wipe the plugs and their threads clean with a shop towel.
    • Hand-thread both drain plugs back into their respective holes.
    • Torque the crankcase drain plug to 14 ft-lbs, and the oil tank drain plug to 17 ft-lbs.
    • If gaskets or sealing washers are worn, replace them to prevent leaks.
  • Remove the Exhaust Pipe (For Oil Filter Access):–
    • Loosen the clamp connecting the exhaust pipe to the muffler using a flathead screwdriver.
    • Use a 5 mm Allen wrench to remove the bolts at the engine cylinder.
    • Carefully pull the exhaust pipe forward to separate it from the cylinder and muffler.

    Note:– This step is required to reach the oil filter on the YZ400F; don't skip it.

  • Replace the Oil Filter:–
    • At the front of the right engine crankcase cover, use a 4 mm Allen wrench to remove the lower oil filter cover bolt.
    • Drain remaining oil from the filter housing into your catch pan.
    • Use a 10 mm socket to unscrew the two upper oil filter cover bolts.
    • Remove the oil filter cover and the filter itself.
    • Clean the filter cover and sealing surface, install a new filter, and reattach the cover and bolts.
  • Reattach the Exhaust Pipe:– Fit the pipe back into place and tighten all bolts and the clamp securely.
  • Reinstall the Skid Plate:– Bolt the skid plate back on with the proper sockets.
  • Refill with New Oil:–
    • Remove the oil tank cap (between the fuel tank and handlebars).
    • Using a funnel, pour in the recommended oil amount and type for your YZ400F.
  • Start the Engine:–
    • Run the engine for about one minute, then shut off and let it sit for a minute.
    • Check for leaks around the drain plugs and oil filter cover.
    • Check the oil level with the dipstick, and top off if necessary.

YZ400F-Specific Tips & Call-Outs

  • Dry Sump Oil System:– The frame itself acts as an oil reservoir. Always remember to drain both the frame (oil tank) drain plug and the crankcase drain plug for a complete oil change.
  • Oil Filter Access:– Accessing the oil filter requires removal of the exhaust pipe—unique compared to many other bikes. Have new exhaust gaskets on hand in case of wear or damage during removal.
  • Multiple Drain Plugs:– Don't overlook any of the oil drains; failing to drain one can mix old oil with new.
  • Torque Settings Matter:– Overtightening drain plugs is a common reason for stripped threads—use a torque wrench and follow recommended specs (14 ft-lbs for crankcase, 17 ft-lbs for frame/oil tank).
  • Proper Disposal:– Dispose of used oil and the filter according to your local environmental regulations.

Changing the oil and filter on the 1999 Yamaha YZ400F takes a bit of time and the right tools, but it's essential for longevity and performance. For trusted parts and accessories, always visit MotoSport.com—your one-stop shop for all Yamaha YZ400F maintenance needs.

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Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.