How to Change the Oil in a 1978 Suzuki RM250: Step–by–Step Guide
Shop parts for a 1978 Suzuki RM250 Dirt Bike.
Changing the oil in your 1978 Suzuki RM250 is key for maintaining engine performance and longevity. While oil changes for dirt bikes like the RM250 are a straightforward process, there are specific steps and Suzuki-specific quirks you should know about—especially with vintage two-strokes. This guide from MotoSport.com provides a comprehensive breakdown, including required tools, step-by-step procedures, and essential tips for the RM250's unique design.
Tools & Supplies Needed
- Socket wrench set (with correct metric sockets for drain plug and filler cap, typically 12mm-17mm for Japanese two-strokes)
- Allen/hex key set (for oil check bolt access)
- Drain pan/oil catch container
- Funnel
- Clean rags or shop towels
- Replacement transmission oil (Recommended: SAE 10W-40, type for two-stroke gearboxes)
- Torque wrench (optional but recommended for re-tightening drain plug to spec)
- Parts cleaner or brake cleaner (optional, for cleaning drain plug and area)
- New crush washer or gasket (recommended whenever replacing oil to prevent leaks)
Preparation
- Warm up the engine for about 2-3 minutes. This helps the oil drain more thoroughly by reducing viscosity. Do not overheat–a short idle suffices.
(Always let the bike cool slightly for safety before proceeding, as both the oil and engine cases can become hot.) - Place the bike upright on a stand or securely balanced, ensuring it's level for accurate draining and refilling.
(Tip: Always work on a level surface. Spilled oil is both messy and hazardous.)
Steps to Drain and Replace the Transmission Oil
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Remove the filler cap:
- Locate the oil filler cap on the crankcase. Remove it to allow freer flow when draining oil and prevent vacuum lock.
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Place your drain pan underneath the engine's drain plug.
- Position it slightly forward and to the left of the center stand for the RM250. Ensure the pan is large enough for at least 1 liter.
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Remove the drain plug:
- Use the correct socket to loosen and remove the drain plug underneath the transmission case. Let the old oil drain completely into your pan.
- Inspect the drain plug and washer–replace the washer if it's damaged or crushed to prevent leaks upon reinstallation.
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Optional: Clean and inspect drain plug.
- The RM250's drain plug often includes a magnet to catch metal debris. Wipe it clean with a rag and inspect for excessive filings, as this might indicate abnormal wear.
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Replace and torque the drain plug:
- Reinstall the drain plug by hand, ensuring it's not cross-threaded. Tighten securely–reference torque specs in your service manual if available, typically around 21 N·m (15.0 lb-ft) for Suzuki two-stroke transmission plugs.
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Add new transmission oil:
- Insert a funnel into the filler hole and pour in fresh 10W-40 transmission oil. For the 1978 RM250, 750 ml is the standard refill volume after draining. Do not overfill.
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Check oil level:
- The RM250 is equipped with a dedicated oil check bolt to verify correct oil level. On the 1978 model, this bolt is often hidden behind the chain guard and may require moving a wire bundle. Use an Allen key to loosen and remove the oil check bolt.
- Add oil in small increments until oil just begins to seep out of the check bolt hole when upright and level. This ensures precise filling.
- Reinstall and tighten the check bolt after level verification.
- Reinstall the filler cap and wipe down any drips.
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Start and idle the engine for 1-2 minutes.
- This allows new oil to circulate and air bubbles to escape. Shut off the engine and re-check the oil level via the check bolt. Top off if necessary.
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Dispose of used oil properly.
- Take the spent transmission oil to a recycling center or designated hazardous waste facility.
Model-Specific Call-Outs for the 1978 Suzuki RM250
- The 1978 RM250 is a two-stroke, and its oil change procedure targets transmission/gearbox oil—not premix oil for combustion.
- The oil check bolt can be tough to locate for new owners. It's hidden behind the chain guard and some wiring—removing the guard and gently moving wires may be necessary .
- The gearbox volume is 750 ml; overfilling causes excessive drag, leaks, or foaming.
- If your RM250 has been previously modified, double-check for any aftermarket covers or plugs; always refer to your specific bike if something looks different than described above.
Recommended Oil Type
- SAE 10W-40 motorcycle transmission oil
- Use high-quality oil designed for wet-clutch applications and compatible with two-stroke transmissions. Do not use regular two-stroke premix oil or non-motorcycle oils.
Final Tips
- Always record the date and hours ridden at your oil change interval.
- Inspect oil for metal shavings or milky color (which can indicate water ingress)—address promptly if discovered.
- For frequent or aggressive use, change oil and check transmission fluid more often (every 5-10 hours of riding).
Keep your classic RM250 running strong with careful, regular oil changes–and always trust MotoSport.com for authentic vintage dirt bike care advice.
Related Shopping Categories
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Shop Oil Fillers and Drain Plugs for a 1978 Suzuki RM250 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.