How to Change the Oil in a 2021 Honda CRF150R Big Wheel

Shop parts for a 2021 Honda CRF150R Big Wheel Dirt Bike.

Keeping your 2021 Honda CRF150R Big Wheel running strong means staying on top of routine oil changes. Unlike many other dirt bikes, the CRF150R uses separate engine and transmission oil compartments, so you’ll need to change both fluids to complete regular maintenance. This guide covers the tools you’ll need, step-by-step instructions, and special call-outs specific to this model, ensuring you get the job done right for peak MotoSport.com performance.

Tools and Supplies Needed

  • Socket set and ratchet (primarily 12mm and 8mm sockets)
  • Torque wrench
  • Drain pan (wide enough for easy catching)
  • Funnel (long-neck recommended)
  • Lint-free rags or shop towels
  • New engine oil filter
  • New O-ring or oil filter gasket (replace every oil change)
  • New crush washers (for drain bolts)
  • Engine oil: Honda recommends GN4 10W-40 four-stroke oil
  • Transmission oil: Honda GN4 10W-40 or transmission-specific oil per owner preference
  • Measuring cup (with cc/mL markings)
  • Shop gloves

Model-Specific Call-Outs: 2021 CRF150R Big Wheel

  • This model uses separate oil chambers for the engine and clutch/transmission sides. Each has its own drain plug and fill port

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  • It’s crucial to not over-tighten drain bolts–stripped threads can turn a simple oil change into an expensive repair

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  • Use a new crush washer for each drain bolt at every change for optimal sealing

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  • Oil quantity:
    • Engine side: 590cc (about 0.62 qt) with filter; 560cc (about 0.59 qt) without replacing the filter

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    • Clutch/Transmission side: 580cc (about 0.61 qt)

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  • Only perform the oil level check after starting and running the bike briefly, then letting it cool a few minutes

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  • Always clean the area around the drain and fill plugs before removing to avoid contamination.

Step-by-Step Oil Change Instructions

  1. Preparation:
    • Warm up the engine for 2-3 minutes. This thins out the oil, allowing for a more thorough drain

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    • Turn off the motorcycle and place it on a stable stand or level surface.
    • Use rags to clean any dirt around the drain bolts and oil filter cover.
  2. Drain the Engine Oil:
    • Locate the engine oil drain bolt (on the right side case).
    • Position your drain pan under the engine. Remove the drain bolt and crush washer with a socket/ratchet.
    • Allow oil to fully drain. While draining, remove the engine oil fill cap to let air in for a steady flow

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    • Remove the old oil filter (cover held by 8mm bolts)—note orientation for the new filter install
  3. Install New Oil Filter & Seal:
    • Wipe the filter cavity clean. Install the new oil filter and fresh O-ring or oil filter gasket.
    • Reinstall oil filter cover; snug bolts evenly, then torque per factory spec (usually around 9 Nm, refer to owner’s manual)

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  4. Refit Engine Drain Bolt:
    • Replace the crush washer with a new one. Reinstall the engine drain bolt and torque to manufacturer specs (approx. 24 Nm / 17 lb-ft; check manual for confirmation).
  5. Drain the Transmission (Clutch Side) Oil:
    • Locate and remove the clutch (transmission) side drain bolt (on left case). Drain oil completely.
    • Replace with a new crush washer, torque the drain bolt to spec.
  6. Refill with Fresh Oil:
    • Using a funnel, carefully add 590cc of oil to engine side (if filter is replaced), 580cc to the clutch/transmission side. Do not overfill

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    • Replace both fill caps securely.
  7. Final Steps & Oil Level Check:
    • Start the motorcycle and let it idle for 1-2 minutes to circulate new oil. Shut off and allow to sit for 3-5 minutes.
    • Check oil levels on both sides using the dipsticks or sight glass. Top off if necessary, but don’t overfill.
    • Check for any leaks around the drain bolts or filter cover.

Pro Tips for the 2021 CRF150R Big Wheel

  • Always use high-quality, motorcycle-specific oil for best clutch and engine life

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  • Do not cross-thread any bolt or overtighten, especially on the magnesium case covers—they are fragile

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  • Dispose of used oil and filter responsibly at a recycling facility.
  • If you ride your CRF150R hard or in extreme conditions, consider more frequent oil changes for maximum protection.

Stay ahead of maintenance and keep your Honda at its best—trust the right tools, the right procedure, and proprietary insights from MotoSport.com for every ride.

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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.