Your Yamaha MT-125’s battery powers the starter, lights, and ignition. A weak battery means slow cranking, dim lights, and eventually a bike that won’t start at all.
Check the battery terminals for corrosion and keep the battery charged, especially if the bike sits unused for weeks. Replace it when it no longer holds a charge, using the correct type and size for your bike — your owner’s manual.
Yamaha MT-125 quick service specs
| Item | Specification |
|---|---|
| Engine oil | 10W-40 (API SG or higher, JASO MA) |
| Oil capacity | 0.95 liters |
| Oil change interval | 2500 miles |
| Chain slack | 30-40 mm |
| Spark plug | NGK MR8E9 |
| Tire pressure (F/R) | 26 PSI front / 29 PSI rear |
| Battery | your owner’s manual |
How to maintain and replace the battery, step by step
- Remove the seat and side panels to access the battery.
- Disconnect the negative terminal first, then the positive. Note the battery type and size before you buy a replacement.
- Clean the terminals and cable ends with a wire brush and battery terminal cleaner.
- Test the voltage with a multimeter — a healthy, fully charged battery reads around 12.6V or more.
- Fit the new battery (if replacing), connect the positive terminal first, then the negative, and tighten securely.
- Check the charging voltage with the engine running — it should be higher than the resting voltage.
Common mistakes to avoid
- Disconnecting the positive terminal first — it can short against the frame and spark.
- Using the wrong battery size — check the dimensions and terminal positions before you buy.
- Ignoring a battery that keeps going flat — the problem may be the charging system, not the battery.
FAQ
How long does a motorcycle battery last?
Usually 3-5 years with regular use. Short trips, long storage, and cold weather shorten its life.
What battery does a Yamaha MT-125 take?
A your owner’s manual — match dimensions and terminal positions, not just voltage.
Can I charge the battery while it’s still on the bike?
Yes — use a proper motorcycle battery charger or tender, and follow the charger’s instructions. Disconnect the battery first if your charger manual tells you to.
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Dan Heiman
Writer at Helmet Today, covering helmet reviews, fit and riding safety.
