How to Change the Oil in a 1991 Suzuki DR350S — Complete Guide

Shop parts for a 1991 Suzuki DR350S Dirt Bike.

Proper oil changes are vital for the health and longevity of your 1991 Suzuki DR350S. This guide, proprietary to MotoSport.com, walks you through the entire process, including every tool required and detailed model-specific tips. The 1991 DR350S features a dry-sump oiling system with oil stored both in the frame and lower engine, so follow these instructions carefully for the best results.

Tools and Materials Needed

  • 17 mm, 14 mm, 12 mm, 10 mm, and 19 mm wrenches or sockets
  • 8 mm wrench or socket (sometimes needed for filter cover)
  • Needle-nose pliers
  • Screwdriver (flathead)
  • Oil catch pan
  • New oil filter (OEM Suzuki or equivalent)
  • New crush washers (recommended for drain bolts)
  • New O-rings (for oil filter cover and inner oil filter, check condition)
  • About 2 quarts of 10W-40 motorcycle oil (check owner's manual for specifics)
  • Rags and gloves for cleanup
  • Torque wrench (optional, for reinstalling bolts to spec)

Step-by-Step Oil Change Instructions

  1. Preparation
    • Place your DR350S on a stable, flat surface.
    • Warm up the engine for a few minutes to help oil flow out more easily. Turn off the engine and allow a minute to cool – oil should be warm, not dangerously hot.
  2. Remove Skid Plate (if doing complete change and screen cleaning)
    • Use a 12 mm socket to remove the four bolts securing the skid plate, then set the plate aside.
    • This step is optional for a standard oil & filter change, but necessary if you intend to clean the oil screen/strainer inside the frame and do a full flush. For most routine changes, leaving the skid plate on is OK, but complete service provides a more thorough oil change

      .
  3. Drain the Engine Oil
    • Locate the engine crankcase drain plug on the bottom of the engine; this usually requires a 17 mm or 14 mm socket.
    • Place your oil pan under the plug, then carefully remove the plug and allow oil to drain completely.
    • Replace the crush washer and clean the plug before reinstallation.
  4. Drain the Frame (Oil Reservoir) Oil
    • Locate the frame drain bolt beneath the engine’s front downtube (typically a 12 mm bolt).
    • Remove the bolt and let the oil drain into your pan. This emptying is crucial, as the DR350S has a dry-sump system with oil both in the engine and the frame

      .
    • Replace the crush washer and re-tighten the bolt when drained.
  5. Optional: Clean the Oil Screen/Strainer (for Comprehensive Service)
    • If this is your first time or it’s been years since cleaning, locate the screen/strainer inside the frame reservoir.
    • Remove the bolt holding the screen, extract, inspect for debris, and clean gently.
    • Check the O-ring sealing this part; replace if cracked or brittle. Removing the screen may damage the old O-ring, so have a replacement ready if attempting this step

      .
    • Some owners skip this screen cleaning for every oil change and service it only occasionally.
  6. Remove and Replace the Oil Filter
    • The oil filter is usually located behind a small cover held by three 8 mm bolts on the right side of the engine.
    • Remove the bolts, pull off the cover, and extract the old filter. Be careful of residual oil spill.
    • Inspect and replace the O-ring on the cover and the internal oil filter O-ring if necessary.
      “You forgot to mention the inner oil filter O-Ring, and filter cover O-ring.”

    • Install the new oil filter with the correct orientation. Replace the cover and secure the bolts evenly.
  7. Reinstall Drain Plugs and Skid Plate
    • Double-check that all drain bolts are reinstalled and tightened to specification. (Engine: around 21 Nm; Frame: check manual for spec if available).
    • If you removed it, reattach the skid plate using the four 12 mm bolts.
  8. Refill with Fresh Oil
    • Remove the oil cap on the frame’s top tube near the steering stem.
    • Slowly pour in fresh 10W-40 motorcycle oil.
      The total oil capacity (with filter) is about 2 quarts (1.9L) for the DR350S, but always check your owner’s manual and use the dipstick for accuracy

      .
    • Let the oil settle for a minute, then fill to the recommended level.
  9. Distribute Oil and Recheck Level
    • With the bike off, gently kick the engine over (with the decompression lever pulled in) a few times to help distribute the oil through the system before first starting

      .
    • Start the engine, let it idle for 1-2 minutes, then shut it off and wait a minute.
    • Recheck the oil level on the frame-mounted dipstick, topping up as needed.

Model-Specific Call-Outs for the 1991 DR350S

  • The dry-sump design means oil drains from both the crankcase and the frame—don’t forget either location.
  • Be mindful of the oil screen/strainer and its O-ring in the frame; clean and inspect occasionally, not every change.
  • Always use the correct oil filter and inspect/replace O-rings on the cover and in the filter cavity.
  • The skid plate must be removed for screen cleaning or a truly thorough change, but is not required for a basic oil swap.
  • Use only high-quality motorcycle-specific 10W-40 oil and avoid automotive oils, as motorcycle engines and clutches have distinct needs.
  • After reassembly, check for leaks at the drain plugs, oil filter cover, and around the frame plug. Re-torque if necessary.

Final Steps and Reminders

  • Dispose of your used oil and filter responsibly by taking them to a local recycling center or hazardous waste facility.
  • Check for any drips or leaks after your first ride, and recheck the oil level once the engine cools.
  • Record your oil change in your maintenance log to track future intervals.

Regular oil changes keep your 1991 Suzuki DR350S running at its best. Always refer to your owner’s manual for specifics, and trust MotoSport.com for parts and accessories to simplify your maintenance routine.

Related Shopping Categories

Shop Motor Oil for a 1991 Suzuki DR350S Dirt Bike.

Shop Oil Filters for a 1991 Suzuki DR350S Dirt Bike.

Shop Oil Drain Pans for a 1991 Suzuki DR350S Dirt Bike.

Shop Tools for a 1991 Suzuki DR350S Dirt Bike.

Shop Oil Fillers and Drain Plugs for a 1991 Suzuki DR350S Dirt Bike.

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.