4 Cycle FULL CRANK Straight Shaft String Trimmer

Model: #RY4CSS | Home Depot Sku #: 1002145352

The 4 Cycle Straight Shaft String Trimmer brings power, less hassle, and performance to your lawn maintenance. The 4 cycle low emission engine and REEL-Easy bump feed string head make trimming your yard a breeze while keeping the air around you cleaner. The straight shaft allows for extended reach trimming under decks, around obstacles, and in hard to reach places. With the RYOBI 4 Cycle string trimmer, you no longer have to worry about mixing gas and oil. This innovative unit is attachment capable, accepting all nine of the Expand-It universal outdoor attachments. Backed by a RYOBI 3 year warranty while offering less hassle and mower power, the RYOBI 4 Cycle Straight Shaft Trimmer is the residential string trimmer of choice.

Product Videos


No Mixing of Gas and Oil

Attachment Capable: Accepts universal outdoor attachments

Powerful 4 Cycle low emission engine

REEL-EASY™ bump-feed string head for fast and easy reloading

18 in. cut width with .095 in. dual line

Straight shaft for extended reach

11.8 lbs.

3-year limited warranty

  • Engine Type: 4 Cycle/Stroke Low Emission Engine
  • Trigger: Variable Speed Throttle
  • Cutting Path: 18 in cutting swath
  • String Diameter: .095 in. dual line
  • Line Advancement: Bump Feed
  • Attachment Coupler: universal attachment coupler
  • Weight: 11.8 lb.
  • S430 Straight Shaft String Trimmer
  • Ergonomic Front Handle
  • Straight Shaft Grass Guard/Deflector
  • ReelEasy™ String Head
  • 4 Stroke Engine Lubricant
  • Funnel
  • Operator’s Manual

What is the best way to cut weeds and grass using my string trimmer?

  • Keep your string trimmer tilted toward the area being cut
  • Pass the unit from left to right (if using a curved shaft string trimmer) and from right to left (if using a straight shaft string trimmer). By following these directional cutting paths, you will avoid having debris and grass clippings from being directed back at yourself.
  • Use the top of the line to do the cutting. Do not force the string head into uncut grass; this could cause the trimmer to bog down.
  • Avoid trees, shrubs wire and picket fences.

How do I advance the line on my REEL-EASY™ String Head?

Line advance is controlled by tapping the string trimmer head on grass while running engine at full throttle

  • Run the engine at full throttle
  • Tap the knob on ground to advance line. The line advances each time the knob is tapped. Do not hold the knob on the ground

NOTE: The line trimming cut-off blade on the grass deflector will cut the line to the correct length

NOTE: If the line is worn too short, you may not be able to advance the string by tapping it on the ground. If so, stop the engine and manually advance the line.

How do I manually advance the line on my REEL-EASY™ String Head?

  • Stop the engine and disconnect the spark plug wire to ensure you will not be harmed
  • Push the knob in while pulling on line(s) to manually advance the line

How do I replace the line on my REEL-EASY™ String Head?

  • Stop the engine and disconnect the spark plug wire to ensure you will be safe while replacing the line.
  • Rotate the spool clockwise as necessary to align the arrows on the spool.
  • Cut one piece of trimmer line at approx. 20ft. in length. Insert the line in the eyelet on the string trimmer housing. Push until the end of the line comes out the opposite side of the string head. Pull the line from the other side until equal amounts of line are on both sides of the spool.
  • Rotate the spool clockwise to wind the line on the spool until approx. 6 in. of line is showing on each side.
  • Push the spool retainer down while pulling on line(s) to manually advance line and to check for proper assembly of the on the string head.

How do I stop my RYOBI Gas String Trimmer?

To stop the engine, depress the STOP switch to the stop position

How do I remove the attachment from my RYOBI Power Head?

  • Stop the engine and disconnect the spark plug (if a gas unit), remove the battery (if using RYOBI 40V Power Head)
  • Loosen the knob at the connection point
  • Push in the button and twist the shafts to remove and separate the Power Head from the Attachment

How do I install my attachment to my RYOBI Power Head?

  • Stop the engine and disconnect the spark plug (if using a RYOBI Gas Power Head); remove the battery (if using the RYOBI 40V Power Head).
  • Loosen the knob on the coupler of the power head shaft and remove the end cap from the attachment (black rubber piece with loop hole for hanging).
  • Push in the silver button located on the attachment shaft. Align the button with the guide recess on the Power Head coupler and slide the two shafts together. Rotate the attachment shaft until the button locks into the positioning hole.

NOTE: If the button does not release completely in the positioning hole, the shafts are not locked into place. Slightly rotate from side to side until the button is locked into place.

  • Tighten the knob securely.

How do I attach the front handle to my RYOBI Gas String Trimmer?

  • Remove the wing nut, washer, and bolt from the front handle.
  • Install the front handle onto the top side of the drive shaft housing in the area indicated by the label.

NOTE: The open side of the handle should face the user

  • Place the bolt through the front handle

NOTE: the hex bolt head fits inside the hex recess molded into one side of the handle.

  • Reinstall the washer and wing nut.
  • Tighten wing nut securely.

How do I attach the grass deflector to my gas string trimmer?

  • Remove hex screw, washer, and wing nut from the grass deflector.
  • Press the grass deflector onto the bottom of the shaft.
  • Insert the hex screw through the grass deflector and the bracket on the shaft.
  • Place the washer on the hex screw.
  • Place the wing nut on the hex screw and tighten securely.

How do I add engine lubricant to my RYOBI 4 Cycle Unit?

NOTE: Check lubricant level before each use. For best performance, engine lubricant should be changed after every 25 hours of operation.

  • Unscrew the oil cap/dipstick and remove from your unit.
  • Using a funnel (one was provided), add engine lubricant through oil fill hole; fill.
  • Reinstall the oil cap/dipstick and secure.

How do I check my engine lubricant level on my RYOBI 4 Cycle unit?

  • Ensure your unit has been turned off.
  • Unscrew the oil cap/dipstick and remove.
  • Wipe dipstick clean; re-seat in hole and rethread.
  • Remove dipstick again and check the lubricant level. Lubricant level should fall within the hatched area on the dipstick.
  • If level is low, add engine lubricant until the fluid level rises to the upper portion of the hatched area on the dipstick.
  • Replace and secure the oil cap/dipstick.

How do I start my RYOBI 4 Cycle String Trimmer?

To start a cold engine:

  • Slowly press the primer bulb 10 times.

NOTE: After the 7th press, fuel should be visible in the primer bulb. If it is not, continue to press the primer until you see fule in the bulb.

  • Set the choke lever to FULL CHOKE position.

NOTE: Do not squeeze the throttle trigger.

  • Pull the starter grip until the engine runs.

NOTE: If engine has not started after 3 pulls and:

  • Outside temperature is 60 F or lower, leave the choke to the FULL CHOKE position and continue to pull the starter grip until the engine runs.
  • Outside temperature is above 60 F, move the choke to the HALF CHOKE position and continue to pull the starter grip until the engine runs.
  • Allow the engine to run for 10 seconds, then set the choke lever to the RUN position.

To start a warm engine:

  • Slowly press the primer bulb 10 times.
  • Set the choke lever to the RUN position.
  • Pull the starter grip until the engine runs. Do not squeeze the throttle trigger.

How do I clean the air filter on my RYOBI 4 Cycle String Trimmer?

NOTE: For proper performance and long life, keep air filter screen clean.

  • Remove the air filter cover. To remove, push on the latch at the bottom of the cover and gently pull the cover up.
  • Remove the air filter.
  • Clean the foam filter element with warm soapy water. Rinse and let dry.

NOTE: if the foam filter element is damaged, it should be replaced.

  • Apply a light coat of engine oil to the foam filter element, then squeeze it out.
  • Reinstall the air filter.

NOTE: Make sure the filter is seated properly inside the cover. Installing the filter incorrectly will allow dirt to enter the engine, causing rapid engine wear.

  • Replace the air filter cover by placing the slots on the air filter cover of the tabs on the housing, then push the cover down until it latches securely in place.

How do I store my 4 Cycle String Trimmer?

  • Clean all foreign material from the product. Store idle unit indoors in a dry, well-ventilated area that is inaccessible to children. Keep away from corrosive agents such as garden chemicals and de-icing salts.
  • When storing the product vertically, do so with the engine up to avoid hydraulically locking the engine due to oil entering the combustion chamber.

When storing 1 month or longer:

  • Drain all fuel from tank into a container approved for gasoline. Run engine until it stops.

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Click the link below to access outdoor products replacement parts schematics and order parts online.

For those customers that prefer ordering by phone, simply contact the RYOBI master parts distributor at toll free 1-877-634-5704, and place your order over the phone.

Visit Ryobi Lawn & Garden Parts Store

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