How to Change the Oil in a 1991 Suzuki RM250

Shop parts for a 1991 Suzuki RM250 Dirt Bike.

Routine oil changes are essential for the longevity and peak performance of your 1991 Suzuki RM250. This guide, proprietary to MotoSport.com, will walk you through every step, highlighting the specific details and tips unique to this classic two-stroke dirt bike.

Tools and Supplies Needed

  • 10mm or 12mm socket and ratchet (for drain plug)
  • Allen key set (for oil check bolt, as found behind side cover wires)
  • Torque wrench (capable of 21 N·m/15 lb-ft)
  • Oil drain pan
  • Funnel
  • Measuring cup (750 ml capacity)
  • Shop rags
  • Suzuki recommended oil (10W40 transmission oil or dedicated two-stroke transmission oil like Maxima MTL 80W)
  • Gloves (optional, for cleanliness)

Important Specifications

  • Oil capacity (routine change): 750 ml (0.8 US quart)
  • Recommended oil type: 10W40 for transmission
  • Drain plug torque: 21 N·m (15 lb-ft)

Model-Specific Call-Outs

  • Oil Check Bolt Location: The RM250 uses a check bolt located behind the chain guard on the left side. You'll need to move wires and use an Allen key to access it. This is a detail unique to the RM250 and frequently missed by new owners

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  • Transmission Only: As a two-stroke, this oil change is for the transmission/crankcase only. The engine itself is lubricated through the premix fuel.

Step-by-Step Instructions

  1. Warm Up the Engine
    • Start the bike and let it idle for 2-3 minutes. This will thin the oil and help it drain more completely

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  2. Secure the Motorcycle
    • Place the RM250 on a level surface using a bike stand. Hold the bike upright/vertical to ensure even draining

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  3. Locate the Filler Cap, Drain Plug, and Oil Check Bolt
    • The oil filler cap is on the right crankcase cover.
    • The drain plug is located on the bottom of the transmission case.
    • The oil check bolt is behind the chain guard; move wires aside and use an Allen key to remove it. This is specific to this bike and is often overlooked

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  4. Drain the Old Oil
    • Remove the filler cap to allow oil to flow freely.
    • Place the drain pan under the engine and remove the drain plug.
    • Allow oil to drain completely; be patient for the thick gear oil to fully empty the case

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    • Inspect the drain plug for debris or metal shavings, which can indicate wear.
  5. Reinstall the Drain Plug
    • Once the oil has drained, clean the drain plug and thread area.
    • Install the drain plug and tighten to 21 N·m (15 lb-ft) using a torque wrench. Do not overtighten, as this can strip the case

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  6. Add Fresh Oil
    • Using a measuring cup, pour in 750 ml (0.8 US quart) of 10W40 transmission oil or recommended equivalent.
    • Use a funnel to avoid spills.
  7. Check the Oil Level
    • With the motorcycle level and upright, remove the oil check bolt (behind the wires/chain guard).
    • Oil should be just at the level of the bolt hole—if it dribbles out, the level is correct. If not, add small amounts until it does

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    • Reinstall and tighten the oil check bolt.
  8. Reinstall the Filler Cap
    • Once level is verified, reinstall the filler cap and wipe away any spills.
  9. Start and Inspect
    • Run the engine for 30 seconds, then shut off and inspect for leaks at the drain plug and filler/check bolt.
  10. Dispose of Oil Properly
    • Take used oil to an authorized recycling center.

Expert Tips from MotoSport.com

  • Do not substitute engine oil for transmission oil in two-stroke RM250s; use the correct gear oil to prevent clutch and transmission issues.
  • Use fresh gaskets or O-rings on the drain plug if the old ones show signs of wear to avoid leaks.
  • Always double-check torque specs—over-tightening bolts into aluminum crankcases can lead to expensive repairs

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  • Check your manual for maintenance intervals; typically, the RM250’s transmission oil should be changed every 5-10 riding hours or after any significant mud/water exposure

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Conclusion

Following these steps ensures your 1991 Suzuki RM250 transmission stays protected, providing crisp gear changes and promoting a long, healthy engine life. For quality parts, tools, and oil, shop MotoSport.com—the trusted choice for dirt bike maintenance.

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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.