STIHL FS 56 string trimmer (FS 56, FS 56 R, FS 56 C, FS 56 RC)
The FS 56 is STIHL's 27.2cc two-stroke homeowner trimmer. The R versions have a loop handle instead of a bike handle, and the C versions have Easy2Start.
FS 5627.2 cm32-stroke
Specs and part numbers at a glance
- Displacement
- 27.2 cm3 (1.66 cu in)
- Spark plug
- NGK CMR 6 H (resistor type)
- Plug gap
- 0.5 mm (0.02 in)
- Fuel mix
- 50:1 gasoline to two-stroke oil (STIHL oil or an equivalent air-cooled two-stroke oil; not BIA or TCW outboard oil)
- Gasoline
- 89 octane or higher, no more than 10% ethanol
- Fuel tank
- 0.34 L (11.5 fl oz)
- Idle speed
- 2,800 rpm
- Weight, dry
- FS 56 5.1 kg (11.3 lb), FS 56 R 4.7 kg (10.4 lb)
Find the model number
The serial number plate is marked # in the main parts drawing in the STIHL manual. The model name, such as FS 56 RC, is printed on the trimmer. STIHL's manual search accepts the model name or the serial number.
Parts and part numbers
Check the number against the parts list for your exact model before you order.
| Part | Part number | Notes |
|---|---|---|
| Spark plug | NGK CMR 6 H | STIHL FS 56 instruction manual. Use only resistor plugs with a solid terminal. |
Tools you need
- Spark plug wrench
- Wire-type gap gauge
- Clean fuel can for 50:1 mix
- Gloves and eye protection
Maintenance and repairs, step by step
Start a cold engine
From the STIHL FS 56 manual.
| 01 | Press the manual fuel pump bulb at least 5 times, even if it already looks full. | |
| 02 | Press in the choke lever and turn it to the cold start position. | Use the warm start position if the engine has run but cooled a little. |
| 03 | Set the trimmer on the ground, resting on the engine support and deflector. Check the line head is not touching anything. | |
| 04 | Hold it down with your left hand. Don't touch the throttle trigger or lockout. | Don't stand or kneel on the drive tube. |
| 05 | Pull the starter grip slowly until it engages, then give it a brisk pull. On C versions, just pull steadily. | Don't pull the rope all the way out, and don't let it snap back. |
| 06 | Keep pulling until the engine runs. Squeeze the throttle trigger once to release the choke to the run position. |
Clean the air filter
When the engine loses power.
| 01 | Move the choke lever to the warm start position. | |
| 02 | Loosen the screw on the filter cover and lift the cover off over the choke lever. | |
| 03 | Clean loose dirt from around the filter, then take the filter out. | |
| 04 | Replace a damaged filter. Fit the filter and cover back in place. |
Check and replace the spark plug
Replace after about 100 hours, or sooner if the electrodes are worn.
| 01 | Shut off the engine and pull off the plug boot. | |
| 02 | Unscrew the plug and clean it. | |
| 03 | Check the gap and set it to 0.5 mm (0.02 in) if needed. | Fouling usually means too much oil in the mix, a dirty air filter, or a lot of part-throttle running. |
| 04 | Screw the plug in and press the boot firmly onto it. | STIHL warns against plugs with a loose screw-on terminal: they can arc and start a fire. |
Feed line on an AutoCut head
| 01 | With the engine running, hold the spinning head just above the grass. | |
| 02 | Tap it on the ground once. Fresh line feeds out and the blade on the deflector trims it to length. | |
| 03 | Don't tap more than needed: each tap feeds line. | Feed only works if both lines are at least 2.5 cm (1 in) long. |
Troubleshooting by symptom
| Symptom | Likely cause | What to do |
|---|---|---|
| Won't start | Not enough priming, wrong choke position, or stale mix | Press the bulb at least 5 times, use the cold start position, and mix fresh 50:1 fuel. |
| Starts, runs poorly | Dirty air filter or fouled plug | Clean the filter, check the plug gap. |
| Loses power | Clogged air filter or blocked spark arresting screen in the muffler | Clean the filter. STIHL sends the muffler screen to a dealer if you are unsure. |
| Line won't feed | Line shorter than 2.5 cm or empty spool | Shut off the engine and reload the head as shown in the instructions supplied with the head. |
Owner's manuals and parts lookups
These go to the maker's own sites.
- STIHL USA instruction manuals Search FS 56
Something wrong or missing?
Tell us the full model number on your engine and what you found.