How to Change the Oil in a 1991 Suzuki DR350

Shop parts for a 1991 Suzuki DR350 Dirt Bike.

Keeping your 1991 Suzuki DR350 running smoothly requires regularly changing the oil. While oil changes are a straightforward aspect of maintenance, the DR350—s unique dry sump system and frame-reservoir oil storage make this process a bit different from more typical motorcycles. This detailed, MotoSport.com-proprietary guide covers every step, all necessary tools, and model-specific insights so you get the job done right every time.

Tools & Supplies Needed

  • 10mm, 12mm, 14mm, 17mm, 19mm socket wrenches
  • Socket wrench extension (optional)
  • Flathead screwdriver
  • Needle-nose pliers (for cleaning the oil strainer, optional)
  • Drain pan (to catch spent oil)
  • New oil filter (OEM or Hiflofiltro HF133 or equivalent)
  • Fresh oil (2 quarts of high-quality 10W40 motorcycle oil)
  • New crush washers and filter O-rings (recommended, especially if they show wear)
  • Shop towels or rags
  • Rubber gloves
  • Torque wrench (optional, for precise reassembly)

Important Facts for the 1991 Suzuki DR350

  • The DR350 uses a dry sump oiling system—in addition to draining the crankcase, you must also drain the oil stored in the frame.
  • An oil screen (strainer) is built into the down tube of the frame. Cleaning it isn’t necessary for every oil change but recommended every few changes, or if you suspect debris in your oil.
  • The oil filter cover uses an O-ring that should be inspected every oil change—replace if it is cracked or flattened.
  • Removing the skid plate (four 12mm bolts) makes accessing drain bolts and the strainer easier, although it’s not absolutely required unless you’re cleaning the oil strainer.

Step-by-Step Oil Change Instructions

  1. Warm up the engine.
    • Start the motorcycle and let it idle for 2-3 minutes. Warm oil drains more easily and completely.
  2. Secure the bike safely and remove the skid plate (if needed).
    • If you plan to clean the oil strainer, remove the four 12mm bolts securing the skid plate and place it aside.
    • Otherwise, you can often reach both drain plugs without removing it, but it’s easier with the plate off.
  3. Remove the oil fill cap/dipstick.
    • This relieves pressure and helps oil flow out quickly and smoothly.
  4. Drain the engine oil from the crankcase.
    • Place your drain pan under the engine.
    • Use a 17mm (or 14mm, depending on prior replacements) socket to loosen and remove the crankcase drain bolt (located beneath the engine). Allow oil to drain fully.
    • Inspect the crush washer; replace if it’s worn or damaged.
  5. Drain the oil from the frame reservoir.
    • Locate the frame drain bolt at the bottom of the frame downtube (often 12mm or 19mm socket required).
    • Remove this bolt and let all oil drain into your pan.
    • Replace the crush washer if necessary.
  6. Clean the oil screen (optional, but recommended every few oil changes).
    • With the frame drain bolt out, use needle-nose pliers to carefully remove the oil screen (strainer) from the down tube. Clean any debris from it with solvent and dry thoroughly.
    • Inspect the O-ring and replace if it’s worn or damaged.
    • Reinstall the screen and frame drain bolt, tightening securely.
  7. Replace the oil filter.
    • Locate the oil filter cover (right side of the engine, 8mm or 10mm bolts).
    • Remove the bolts and cover, then take out the old filter. Note orientation for the new filter install.
    • Check two O-rings: one on the filter cover, one inside near the engine—replace if needed.
    • Grease the new O-rings lightly, install the new filter (writing or open end outwards; verify with your filter’s instructions), and reattach the cover, tightening bolts evenly.
  8. Reinstall drain bolts (engine and frame).
    • Tighten bolts securely, ideally to spec using a torque wrench: 16-22 ft-lb (22-30 Nm) is typical—check your manual.
  9. Add fresh oil.
    • Pour in 1.9-2.1 quarts (1.8-2.0 liters) of 10W40 motorcycle oil via the oil filler in the frame near the neck.
    • Replace the oil fill cap tightly.
  10. Prime the oil system.
    • Before starting, kick the engine over (ignition off, decompression lever pulled) 8-12 times to circulate oil through the system. This helps prevent air locks and ensures the oil pump is primed.
  11. Start the engine and check oil level.
    • Start your DR350 and let it idle for several minutes, checking for leaks around drain bolts and the oil filter cover.
    • Shut off the engine and let sit for 3-5 minutes, then check oil level with the dipstick. Oil should sit between the low and high marks with the bike upright (not on the side stand).
    • Add a small amount if needed, but do not overfill.
  12. Reinstall the skid plate (if removed).
  13. Dispose of used oil and filter responsibly.

Model-Specific Tips for the 1991 DR350

  • The frame reservoir’s oil drain and oil strainer are unique to DR350 dry sump bikes; do not skip draining the frame or cleaning the strainer (at least every few oil changes).
  • Only use motorcycle-specific 10W40 oil; car oil can cause clutch slippage and increased wear.
  • Always check and, if necessary, replace both O-rings (filter cover and inside the filter cavity) to prevent leaks.
  • Don’t overtighten filter cover or drain bolts; stripping threads in the aluminum cases is a common error.

With these clear, step-by-step instructions, you’ll keep your 1991 Suzuki DR350’s engine safely lubricated, prolong its lifespan, and ensure years of reliable riding—MotoSport.com has you covered every step of the way.

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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.