The Stihl MS 261 is a professional 2-stroke petrol chainsaw renowned for its torque and reliability. It's a machine for intensive use that will deliver years of service if properly maintained. Here's the complete owner's guide.
The 2-stroke mix: the foundation of everything
The MS 261 runs on a 2-stroke petrol/oil mix. Getting the ratio right is key to engine longevity.
- Recommended ratio: 1:50 with Stihl HP oil, that is 20 ml of oil per litre of petrol.
- Use fresh petrol, ideally E5 (super unleaded) or low-ethanol blend; E10 is acceptable if your machine is relatively modern.
- Don't prepare more mix than you'll use within a month.
| Petrol | 2-Stroke oil (1:50) |
|---|---|
| 1 L | 20 ml |
| 5 L | 100 ml |
The exact ratio and approved oil for your specific MS 261 version are available via the L'Atelier mechanic AI tool, which draws on manufacturer documentation.
Chain tension and sharpening
A well-tensioned and sharp chain makes all the difference in cutting performance.
- Cold tension: the chain should pull snug against the guide bar yet rotate freely by hand.
- Sharpening: respect the pitch and gauge of your chain, typically guided by the appropriate round file.
- Check the depth limiter wear every two to three sharpenings.
A chain that pulls to one side during cutting often signals asymmetrical sharpening rather than a bent guide bar.
Guide bar maintenance
The bar undergoes constant wear.
- Rotate the bar at each refuelling to balance wear.
- Clean the groove and oil hole regularly.
- Check for burrs along the rails and file them down if necessary.
Air filter and spark plug
| Component | Maintenance |
|---|---|
| HD2 air filter | Regular cleaning; replace if clogged |
| Spark plug | Check gap; clean electrodes |
| Pre-filter | Blow clean with compressed air |
An MS 261 that struggles to start when warm often points to a saturated air filter or worn spark plug before any carburettor fault. The correct spark plug gap for your specific version is provided by the L'Atelier mechanic AI tool.
