How to Change the Oil in a 1980 Kawasaki KX125: A Complete MotoSport.com Guide
Shop parts for a 1980 Kawasaki KX125 Dirt Bike.
Changing the oil in your 1980 Kawasaki KX125 is a fundamental maintenance task that ensures your two-stroke transmission and clutch operate smoothly for years to come. While the KX125 is a vintage model, the process remains straightforward with the right tools and some specific knowledge about this classic dirt bike.
Tools and Materials Needed
- Socket set (including a 17mm socket for the drain bolt)
- Oil drain pan
- Measuring cup
- New transmission oil (see call-outs for weight below)
- Clean funnel
- New crush washer (recommended for drain bolt)
- Clean rags or paper towels
- Torque wrench
- Shop gloves (optional)
Recommended Oil Type and Capacity for 1980 KX125
- Recommended oil weight: 10W40 or 80W gear/transmission oil for most conditions
- This model does NOT use engine oil in the crankcase; it uses a separate oil for the transmission/clutch, as is typical for two-strokes.
- Capacity: Approximately 700ml (Double-check your owner's manual or markings on the side case if you have aftermarket parts installed.)
Step-by-Step Guide
-
Warm Up the Engine
Let the bike idle for a couple of minutes. Warming up the oil helps suspend contaminants and ensures a more complete drain. -
Prepare the Bike
Place the KX125 on a stand so it remains upright and stable. Position your drain pan beneath the drain bolt, which is located at the lowest point of the right-side engine case. -
Remove the Drain Bolt
Use the 17mm socket to carefully loosen and remove the bolt. Allow all old oil to drain into the pan. Inspect the oil for any obvious signs of metal shavings or contamination. -
Replace the Crush Washer
It's a good idea to fit a new crush washer to the drain bolt whenever you remove it to ensure a leak-free seal. -
Reinstall the Drain Bolt
Clean the threads and area around the drain hole with a rag. Thread the bolt in by hand to avoid cross-threading, then use your torque wrench to tighten to the manufacturer's spec (usually around 10–15 ft-lbs for a bolt this size — check your manual for specifics). -
Add New Transmission Oil
Remove the oil fill cap (often on the right side of the engine case). Insert the funnel and pour the measured amount of new oil (about 700ml). It's better to slightly underfill, check the level, then top off if needed. -
Check the Oil Level
Most KX125s have an oil level check bolt or a sight glass near the clutch cover. With the bike upright, remove the check bolt; a small trickle means the level is right. Reinstall the check bolt and cap. -
Wipe Down and Dispose of Oil Properly
Clean any spilled oil. Dispose of the old oil according to local regulations—never pour it down drains or onto the ground. -
Start the Engine and Check for Leaks
Let the bike run for 1–2 minutes. Inspect around the drain bolt and fill cap for leaks. If you see any, turn off the engine and retighten as needed.
Specific Call-Outs for the 1980 Kawasaki KX125
- Vintage Consideration: Gasket and bolt threads may be more prone to wear due to age. Inspect these areas for signs of past leaks, and replace gaskets or seals if needed.
- Sight Bolts and Washers: Over-tightening the old aluminum bolts or using reused washers can strip threads or lead to leaks. Always thread bolts carefully and use fresh washers if possible.
- Aftermarket Covers: If your KX125 has aftermarket side cases or covers, oil capacity and sight/check bolt locations may differ. Confirm oil volume via the manufacturer or by careful observation upon filling.
-
Correct Oil: Always use non-friction modified motorcycle-specific oil. Automotive oils may contain friction modifiers that can degrade clutch performance in this wet clutch two-stroke.
More on popular weights: 10W40 motorcycle oil or 80W gear oil are commonly used and available from most parts suppliers for the KX125.
Pro Tips
- Document your oil change date and hours run for future maintenance planning.
- Inspect the drained oil for signs of clutch wear (metal flakes, burnt smell) – this can be an early warning of trouble and help you avoid major repairs down the line.
- Changing oil on a vintage two-stroke like the 1980 KX125 keeps both the transmission and clutch working their best, especially under the demanding conditions of motocross and off-road riding.
Conclusion
Maintaining your classic 1980 Kawasaki KX125 with regular oil changes will keep it running strong and reliable, whether on the track or trail. For the best performance, always use high-quality oil, follow the correct procedure, and consult MotoSport.com for all your parts and expert advice.
Related Shopping Categories
Shop Motor Oil for a 1980 Kawasaki KX125 Dirt Bike.
Shop Oil Filters for a 1980 Kawasaki KX125 Dirt Bike.
Shop Oil Drain Pans for a 1980 Kawasaki KX125 Dirt Bike.
Shop Tools for a 1980 Kawasaki KX125 Dirt Bike.
Shop Oil Fillers and Drain Plugs for a 1980 Kawasaki KX125 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.