Craftsman 316740890 trimmer Parts

To replace the trimming line on your Craftsman gas line trimmer model 316740890, we install new line in the cutting head (bump head or fixed-line head) using the correct length so it feeds smoothly and does not tangle. Follow the steps in the 316740890 owner's manual.

• Turn the trimmer OFF and wait for the engine to stop completely.
• Let hot parts cool (muffler area can stay hot after shutdown).
• Work on a flat surface and wear gloves and eye protection.
• Use only the line type and size listed in the specifications for this model.

This model’s manual describes a bump head that loads without disassembling the cutting head.

• Remove any old line and clear debris from the eyelets.
• Cut two 10-foot (3.0 m) lengths of new line.
• Cut one end of each line at a 30° angle to help it feed into the eyelet.
• Align the mark on the bump knob with the mark on the spool cover.
• Insert each line into an eyelet and push it in about 3 inches (7.5 cm).
• Turn the bump knob to wind until about 5 inches (12.5 cm) of line sticks out on each side.

Some versions can be used as a fixed-line head. The manual method is:

• Push one end of the old line into the head until a loop protrudes, then pull the loop to remove it.
• Insert the ends of the new line into the holes, push through until both ends protrude from the eyelets.
• Pull ends tight and adjust so both sides are equal length.

Correct line length and even tails help the head feed properly, reduce tangling, and prevent poor trimming performance or stalling when you bump-feed line.

Last updated: February 2026

For Craftsman gas line trimmer model 316740890, the operator’s manual does not list a specific fuel hose inside diameter (ID) or outside diameter (OD). The correct size is the hose that seals tightly in the fuel tank grommet and fits snugly on the carburetor and primer bulb fittings; use the routing shown in the 316740890 operator’s manual.

Use the old hose (or the tank grommet and fittings) as your measuring guide:

• Measure the ID of the old line; it must match the carburetor and primer bulb nipples.
• Check the OD where it passes through the tank grommet; it must seal without leaking air.
• Replace any line that is hard, swollen, cracked, or loose on the fittings.
• If the old line is missing, match hose size by test-fitting on the carburetor and primer bulb ports.
• Confirm the fuel system layout and service points in the manual before cutting new hose.

The manual for this unit includes specifications for trimming line, not fuel line.

A fuel line that does not seal or fit correctly causes air leaks and fuel delivery problems:

• Primer bulb does not fill with fuel
• Hard starting or only starts with repeated priming
• Starts, then stalls when you open the throttle
• Fuel seepage around the tank grommet

On a 2-cycle Craftsman trimmer, the carburetor and primer system need an airtight fuel path. Correct hose fit (ID on fittings and OD at the grommet) prevents air leaks that cause stalling and poor power.

Last updated: February 2026

For the Craftsman 316740890 gas line trimmer, we use 0.095 in. (2.41 mm) trimming line with the bump head. If your trimmer is set up with a fixed-line cutting head instead, it uses 0.110 in. (2.79 mm) (medium) or 0.130 in. (3.30 mm) (large); confirm your cutting head style in the 316740890 operator’s manual.

• Bump head: 0.095 in. (2.41 mm)
• Fixed-line cutting head: 0.110 in. (2.79 mm) medium or 0.130 in. (3.30 mm) large
• Use only the line types listed in the specifications to prevent overheating and poor cutting performance

• Bump head: advances line when you tap the bump knob on the ground
• Fixed-line head: uses pre-cut pieces of line that you feed through eyelets
• If you are unsure, match your head to the diagrams and parts list in the 316740890 operator’s manual

Using the correct diameter helps the engine maintain RPM, keeps the cutting head feeding properly, and reduces heat buildup that can shorten the life of the cutting head and drive components.

Last updated: February 2026