Owner’s manual
How to replace line on Craftsman gas trimmer?
To replace the trimming line on your Craftsman gas line trimmer model 316740870, we install two equal lengths of new line into the bump head eyelets, then wind the bump knob until about 5 inches of line sticks out on each side. For the exact steps and diagrams, use the 316740870 owner's manual.
Replacing line on the bump head (Easy Wind style)
- Shut the trimmer off and let the cutting head stop completely.
- Remove any old line and clear debris from the cutting head.
- Cut two 10-foot (3.0 m) lengths of new trimming line; cut one end of each piece at a 30° angle.
- Turn the bump knob to align the marks on the bump knob and spool cover.
- Insert each angled line end into an eyelet; push in about 3 inches (7.5 cm).
- Turn the bump knob to wind line until about 5 inches (12.5 cm) protrude from each side.
Key tips that prevent jams
- Do not push the bump knob down while winding.
- Keep both line ends even; uneven ends can feed poorly.
- Use the correct line type/diameter listed in the specifications section of the manual.
- If line retracts inside the head, unwind and reset to the 5-inch protrusion.
How bump feed works (and how much line it releases)
When trimming at high speed, lightly tap the bump knob on bare ground or hard soil to release more line. Each tap releases about 1 inch (25.4 mm).
| Situation | What to do | What to avoid |
|---|---|---|
| Line is too short while trimming | Tap bump knob lightly at high speed | Tapping in tall grass (can stall engine) |
| Line wears quickly | Check length often; keep line fully extended | Forcing deep cuts in one pass |
| Line will not feed | Reload line and confirm correct length | Resting cutting head on ground while running |
Parts that commonly relate to line replacement
If the head is damaged or line keeps binding, these parts are often involved:
- Line trimmer 2-in-1 spool, outer 731-12543-5
- Mtd line trimmer cutting line 753-06767
- Line trimmer debris shield 753-06200
Why it matters
Correct line length and even winding keep the bump head feeding smoothly, reduce stalling, and help protect the cutting head from overheating and premature wear.
Last updated: February 2026
Is the .095 trimmer line good?
Yes; for the Craftsman 316740870 gas line trimmer, 0.095-inch (2.41 mm) line is the specified diameter for a bump head, so it is a good all-around choice for trimming and edging when you keep the line at the correct length. See the specs in the 316740870 owner's manual.
What 0.095-inch line is best for
0.095-inch line is a strong, durable size that still feeds well in most bump heads, making it a practical everyday option.
- Cutting grass and light weeds
- Sidewalk and driveway edging
- Trimming around fences, posts, and trees (expect faster wear if you hit hard surfaces)
- General yard maintenance where you want longer line life
When 0.095-inch is not the best choice
Using the wrong line type or oversizing beyond what the head is designed for can cause poor feeding, extra vibration, and overheating.
- If your trimmer is set up with a fixed-line cutting head, use the fixed-line sizes listed for that head
- If line breaks constantly, inspect the eyelets and spool for wear or sharp edges
- If the head will not feed, rewind with the correct winding direction and avoid overfilling the spool
Quick spec check for Craftsman 316740870
| Cutting head type | Line diameter to use | Typical use |
|---|---|---|
| Bump head | 0.095 in (2.41 mm) | Trimming and edging |
| Fixed-line cutting head | 0.110 in (2.79 mm) or 0.130 in (3.30 mm) | Heavier weeds, light brush |
Why it matters
Matching line diameter to the cutting head helps the trimmer feed line smoothly, keeps the engine from working harder than necessary, and reduces premature wear on the spool, eyelets, and debris shield.
Tips to make any line last longer
- Keep the cutting head shield installed; do not extend line beyond the shield length
- Make shallow passes instead of forcing the head into thick growth
- Avoid sustained contact with concrete, brick, and chain link fencing
- With a bump head, check and adjust line length often so it stays fully extended
If you need replacement line, a compatible option we list is mtd line trimmer cutting line 753-06767, and you can also search by model number on Sears PartsDirect.
Last updated: February 2026
What is the fuel mixture for a Craftsman trimmer?
For the Craftsman gas line trimmer model 316740870, we use fresh, clean unleaded gasoline mixed with 2-cycle oil at a 40:1 ratio. Using the correct mix helps the engine start easier, run cooler, and avoid carbon buildup.
Correct mix ratio (40:1)
Use this quick guide to measure accurately:
| Gasoline amount | 2-cycle oil needed (40:1) |
|---|---|
| 1 gallon | 3.2 fl oz |
| 1/2 gallon | 1.6 fl oz |
| 1 quart | 0.8 fl oz |
| 1 liter | 25 ml |
Fuel tips that prevent hard starting
Improper or old fuel is the most common cause of performance problems on 2-cycle trimmers. For best results:
- Mix fuel in an approved fuel container, not in the trimmer tank
- Use fuel that is less than 30 days old
- Shake the container before each refill to re-blend oil and gas
- Avoid overfilling; wipe up spills before starting
- Move the trimmer at least 30 ft away from the fueling spot before starting
For the full fueling and starting steps for model 316740870, follow the owner's manual.
When the fuel mix is wrong: what you will notice
A too-lean mix (not enough oil) and a too-rich mix (too much oil) both cause problems. Here is what typically shows up:
- Too little oil: overheating, loss of power, scoring damage risk
- Too much oil: heavy smoke, fouled spark plug, carbon buildup, rough idle
- Old fuel: hard starting, stalling, poor acceleration
Related parts that can help if it still runs poorly
If the mix is correct and the trimmer still struggles, restricted airflow or fuel delivery is often next. These model-compatible parts are common fixes:
- Line trimmer air filter 751-15514 (dirty filter can cause rich running and stalling)
- Mtd line trimmer carburetor 753-06288 (varnish from old fuel can clog passages)
- Line trimmer fuel tank cap 753-06857 (a venting issue can starve fuel)
Why it matters
A 2-cycle engine depends on the oil in the fuel for lubrication. The correct 40:1 mix protects internal engine parts, reduces overheating, and keeps the carburetor and exhaust system from loading up with deposits.
You can order replacement parts for model 316740870 from the parts list for this model, or search by model number on Sears PartsDirect.
Last updated: February 2026
