STIHL Trimmer Head and Blade Replacement

Learn how to perform trimmer head replacement and trimmer blade replacement on your new STIHL trimmer.

As you use your STIHL trimmer through the years, you will need to swap out trimmer heads and blades from time to time. Before getting started with a replacement, make sure you read through the instruction manual that came with your trimmer. After going through your manual, you can also use the videos and instructions below to help with trimmer head and trimmer blade replacements. Be sure to wear the proper protective gloves while working on your trimmer.

• Check to make sure the appropriate deflector has been attached.
• Block the shaft with a stop pin.
• Screw on the AutoCut® C 25-2 trimmer head in a counterclockwise direction until it reaches the base.
• Tighten the trimmer head while the shaft is still blocked.
• Unlock the shaft by removing the stop pin.

• Attach the AutoCut® C 5-2 trimmer head and screw in a clockwise direction for a couple turns.
• Insert the tap head.
• While holding the trimmer head, push down the tap head and turn it in a clockwise direction until tight.

• Check to make sure the appropriate deflector has been attached.
• Block the shaft with a stop pin.
• Screw the STIHL PolyCut™ C 20-3 trimmer head onto the shaft in a counterclockwise direction until it’s tight.
• Remove the stop pin to unlock the shaft.

• Ensure the FSA 56 unit is powered off and that the battery is removed.
• On the mowing head, depress the two tabs on the side to release the cap.
• Remove the old spool from the mowing head.
• Clean any grass, dirt or debris out of the mowing head.
• Using the AutoCut® 2-2 pre-wound spool, feed the trimmer line through each eyelet on both sides of the mowing head.
• Push the spool into the mowing head.
  
• Align the cap with the two tabs on the side of the mower head and press down. You should hear an audible snap as it clicks into place.
• Pull on the two ends of trimmer line to release the slack.
• Make sure that the length of your trimmer line does not exceed the length on the line limiter.
• If too long, trim the line to the distance of the line limiter.

• Loosen and remove the bolts on the trimmer head.
• Remove the worn blades.
• Add grease around the bolts.
• Insert the replacement STIHL PolyCut™ blades into the head.
• Insert and tighten the bolts to hold the blades firmly in place.
• Repeat the same process for the additional blades.
• Check to ensure that the blades can move without any resistance.

• Check to make sure the appropriate deflector has been attached.
• Place the knife on the thrust plate.
• Attach the thrust washer first, then the rider plate and then the nut.
• Block the shaft with a stop pin.
• Tighten the nut in a counterclockwise direction.
• Unlock the shaft by removing the stop pin.

• For effortless and convenient rewinding, STIHL Inc. recommends rewinding the AutoCut® C 6-2 spool with the head attached to the trimmer.
• Ensure the unit is in the off position. If electric, unplug the trimmer from the power supply. If battery-powered, remove the battery.
• On the trimmer head, align the arrows on the black outer side with the arrows on the white inner rim.
• Feed .080” or .095” diameter trimmer line in one eyelet and out the opposite side of the head.
• An equal amount of line should extend from each eyelet.
• Place your fingers in the spool’s recesses.
• Turn counterclockwise until the remaining line is as close to the line limiter as possible.
• Trim any excess line that extends beyond the line limiter.