STIHL FS 38

STIHL FS 38

The STIHL FS 38 is a lightweight, entry-level gas trimmer designed for small to medium residential yards, featuring a 15-inch cutting width and a 27.2 cc engine that delivers just enough power for grass, weeds, and light brush while remaining easy to maneuver at only about 9.3 pounds. Its compact design makes it ideal for yards with obstacles, flower beds, or tight corners, and it performs best when users employ smooth sweeping motions rather than aggressive hacking. For optimal efficiency, always use the proper 2-stroke fuel mix, warm up the engine correctly with the primer bulb and choke, and regulate throttle so the engine runs smoothly without unnecessary strain. Maintenance is crucial: clean or replace the air filter regularly, inspect the spark plug, clear debris from cooling fins, and ensure fuel is fresh, especially before storage, to prevent stalling, poor performance, or engine damage. Common issues include stalling under throttle, often caused by a dirty carburetor, air filter, or spark plug, and improper line feeding from the trimmer head, which can be mitigated by using the recommended line diameter and following proper threading instructions. Using a harness or strap reduces operator fatigue and improves control during longer trimming sessions, while safety precautions such as eye protection, gloves, and long pants are essential to protect from flying debris. Although the FS 38 is reliable for typical yard work, it is not suitable for dense brush, large acreage, or heavy-duty clearing, and users facing those conditions should consider a more powerful trimmer or brush cutter. With proper care and technique, the FS 38 provides efficient, comfortable, and precise trimming for everyday lawn maintenance.

Yard Size Capabilities & Best Use

• The FS 38 is a lightweight, entry‑level gas trimmer, designed primarily for homeowner use.
• It has a 15-inch cutting width (swath), which gives a decent coverage without being overkill.
• The weight is only about 9.3 lb (4.2 kg), making it easy to maneuver, especially in tighter yards or around landscaping obstacles.
• Because of its size and power (27.2 cc, 0.87 bhp), it’s well-suited for small to medium residential lawns, trimming grass, weeds, and lighter brush — not ideal for dense brush or very large-scale clearing.

Troubleshooting Tips (Common Issues + Fixes)

Here are some common problems with the FS 38 and how to troubleshoot them, plus maintenance recommendations:

a) Starts but Dies / Stalls When Throttling

• Some users report that the trimmer starts up but dies when giving throttle. Possible causes:
  • Flooded engine — too much fuel in the carburetor. Use correct fuel mix and don’t over-prime.
  • Carburetor issues — some FS 38 units may have carb settings off from factory. On Reddit, people reported replacing the carb under warranty helped.
  • Air flow / filter problems — a dirty air filter or blocked intake can starve the engine of air.
  • Spark plug —check the plug; if it’s fouled or not gapped correctly, ignition issues arise.
• Fixes:
  • Clean or replace the air filter regularly.
  • Check the fuel lines, the in-tank filter, and the primer bulb for leaks or cracks. As one user noted, if the bulb doesn’t seal or draw properly, fuel delivery gets messed up.
  • If the carb was faulty, have a dealer inspect or rebuild it — it’s not uncommon per user reports.
  • Check for spark. Some users found no spark due to a bad ignition coil.

b) Maintenance to Prevent Problems

• Air Filter: Clean every ~25 hours or more often in dusty conditions.
• Cooling Fins: Clear debris so the engine doesn’t overheat.
• Fuel: Use fresh fuel. If you store the trimmer for a while, drain the tank or add fuel stabilizer.
• Spark Plug: Inspect, clean, and replace if needed. A bad plug can cause rough running or failure to start.
• Storage: Before long-term storage, run the tank low or empty it, clean, and store in a dry place.

c) Improper Head / Line Feeding

• Some users mention issues with the AutoCut trimmer head; either it's feeding too much line or none at all.
• Suggestions:
  1. Use the correct line diameter (for certain heads, Stihl recommends ~2.0–2.4 mm).
  2. Soaking the line in water before use can make it more flexible.
  3. Spray silicone inside the head to reduce friction.
  4. When re-feeding, make sure you follow the head’s instructions carefully (some heads require threading line in a specific way).

Tips for Best Efficiency / Use

To get the most out of your FS 38 and use it effectively:

1. Warm Start Properly
   • Use the primer bulb (“purge pump”) to prime the carburetor before starting. FS 38 has this to make start-up easier.
   • Use the choke correctly when the engine is cold; gradually move it off choke once the engine starts to run smoothly.
2. Use Right Fuel Mix
   • Use high-quality 2-stroke oil mixed at the proper ratio (check your manual). Old or wrong mix fuel causes performance issues.
3. Optimal Trimming Technique
   • Use smooth, sweeping motions rather than hacking back and forth. This maintains a consistent trim line and reduces load on the engine.
   • Let the tip of the trimmer head do the cutting; don’t force the shaft into thick weeds or dense brush beyond what the FS 38 is designed for.
   • Trim in “passes”: do a first pass at a higher line length (tap to feed), then a second pass to clean up.
4. Manage Engine Speed
   • Avoid revving full throttle constantly. As you trim, regulate throttle so the engine runs efficiently; high enough to cut, but not over-stressed.
5. Regular Maintenance
   • As mentioned, keep air filter clean, check spark plug, clean cooling fins, inspect trimmer head, and make sure fuel is fresh.
   • After every few uses, inspect for loose bolts or loose trimmer head.
6. Use a Harness / Strap (optional but helpful)
   • If you're trimming for extended periods, use Stihl’s basic harness (or similar) to reduce fatigue and improve control. Some retailers note that for longer jobs, a harness “significantly increases comfort.”
7. Safety
   • Always wear eye protection, gloves, and long pants.
   • Be cautious of rocks and debris; use the deflector on the trimmer head to protect yourself.