The Sun Joe MJ408E is a corded electric walk-behind mower for small to medium-sized residential lawns. Its 12-amp motor powers a 20-inch steel blade, while the 3-in-1 design supports bagging, mulching, or side discharge.
MJ408E
electric
cutting width
mowing
Product Gallery
Why It Stands Out
20-inch cutting path
The steel blade covers a broad path for efficient residential mowing.
Three cutting options
Choose bagging, mulching, or side discharge and install only the components for the selected mode.
Seven cutting heights
Adjust the deck from 1.96 to 4.13 inches to suit lawn conditions.
Large collection bag
The detachable grass bag holds up to 14.5 gallons (55 liters) of clippings.
Technical Specifications
| Best use | Small to medium-sized residential lawns |
|---|---|
| No-load speed | 3,400 RPM |
| Blade and cutting width | 20 in. (51 cm) steel blade |
| Cutting-height range | 1.96–4.13 in. (50–105 mm) |
| Height adjustment | 7-position manual adjustment |
| Cutting options | Bagging, mulching, and side discharge |
| Grass-bag capacity | 14.5 gal. (55 L) |
| Drive system | Manual push |
| Sound power level | 96 dB |
| Net weight | 53.2 lb. (24.2 kg) |
| Manual | Find the MJ408E manual |
| Warranty | 2-year limited warranty |
What’s in the Box
- MJ408E electric lawn mower
- Upper and lower handles
- Two upper-handle knob-and-bolt sets
- Two lower-handle knobs
- 14.5-gallon grass collection bag
- Side-discharge chute
- Mulching plug
- Operator’s manual and registration card
Safety Before Mowing
- Do not operate in rain or on damp or wet grass.
- Wear eye protection, sturdy footwear, and close-fitting clothing.
- Remove stones, sticks, wires, toys, and other objects from the mowing area.
- Keep children, bystanders, and pets away.
- Make sure guards, the discharge door, and the selected clipping-control component are installed correctly.
Extension Cord Requirements
| Cord Length | Minimum Wire Gauge |
|---|---|
| Up to 50 ft. (15 m) | 14 AWG |
| 50–100 ft. (15–30 m) | 12 AWG |
Assembly
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Attach the lower handle
Fit the lower handle onto the mower by inserting the mower’s threaded ends through the holes at the lower ends of the handle. Tighten both lower-handle knobs.
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Attach the upper handle
Align the upper and lower handle holes. Insert the bolts from the inside and secure them with the upper-handle knobs.
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Secure the appliance cord
Fasten the cord to the handle with the cable clips so it stays organized during operation.
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Select one cutting mode
Configure the mower for bagging, mulching, or side discharge as described below.
Choose a Cutting Mode
| Mode | Setup |
|---|---|
| Bagging | Lift the rear ejector flap and hook the grass-bag rod ends into the mounting gaps near the wheels. Do not install the side-discharge chute or mulching plug. |
| Side discharge | Lift the side-discharge door, align the chute grooves with the pins beneath the door, and hook the chute into place. Do not install the grass bag or mulching plug. |
| Mulching | Lift the rear ejector flap. Hold the mulching plug by its handle, tilt it approximately 15 degrees, and insert it into the rear-discharge opening. Do not install the grass bag or side-discharge chute. |
Adjust the Cutting Height
| Position | Cutting Height |
|---|---|
| 1 | 1.96 in. (50 mm) |
| 2 | 2.32 in. (59 mm) |
| 3 | 2.68 in. (68 mm) |
| 4 | 2.99 in. (76 mm) |
| 5 | 3.35 in. (85 mm) |
| 6 | 3.74 in. (95 mm) |
| 7 | 4.13 in. (105 mm) |
Start and Stop the Mower
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Secure the extension cord
Push a loop through the cord-restraint holder and around the hook, then connect the mower’s appliance cord.
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Position the cord safely
Place most of the cord near the starting point. Keep it behind you and on the already-mowed area.
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Start on level, short grass
Do not start in tall grass. Hold the handle with both hands and press it down slightly to raise the mower’s front before starting.
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Use the safety-start sequence
Press and hold the safety-lock button, then pull the switch-bar lever toward the handle. After the motor starts, release the safety-lock button while holding the lever.
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Begin mowing
Allow the motor to reach operating speed, then gently lower the mower into cutting position.
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Stop the mower
Release the switch-bar lever. Wait for the blade to stop completely before touching the mower or removing the bag.
Mowing Tips
- Mow only dry grass and use back-and-forth paths rather than circular passes.
- Slow your walking pace in thick grass.
- Avoid removing more than one-third of the grass height in one session.
- Use a higher cutting position for tall grass or uneven ground.
- Keep the extension cord behind you and away from the blade path.
Maintenance and Storage
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Disconnect power
Unplug the mower and confirm all moving parts have stopped.
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Clean after each use
Remove grass and debris with a dry cloth or hand brush. A lightly damp cloth may be used, but do not allow water into the mower.
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Avoid water damage
Never use running water or a pressure washer. Water may damage the switch, plug mechanism, or motor.
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Inspect the mower
Check handles, guards, wheels, nuts, bolts, screws, and the grass bag for wear, looseness, or damage.
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Store indoors
Keep the clean mower in a dry, cool, secure location away from children, fertilizer, rock salt, and other corrosive materials. Do not cover it with solid plastic that may trap moisture.
Blade Care and Replacement
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Position the mower safely
Turn the unplugged mower onto its side on a stable surface.
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Secure the blade
Place a block of wood between the blade and mower deck to prevent movement.
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Remove the hardware
Using a 15 mm wrench or socket, loosen the blade nut and remove the nut, washer, blade insulator, and blade.
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Install the replacement
Position the MJ408E-BLD blade with its curved ends pointing toward the mower deck, then reinstall the blade insulator, washer, and nut in the original order.
Troubleshooting
The motor does not run
Check: Outlet power, circuit breaker or fuse, appliance-cord connection, extension-cord condition, blade obstruction, and the starting sequence.
Try: Reconnect securely, use a working suitable outdoor cord and outlet, clear obstructions only while unplugged, let an overheated motor cool, and restart on short grass using the safety-lock button followed by the switch lever.
Motor power drops
Check: Cutting height, grass density, cord gauge and length, supply voltage, and blocked air vents.
Try: Raise the deck, slow your walking pace, use the required extension cord, confirm proper outlet power, and clean the vents while unplugged.
Cutting performance drops
Check: Incorrect cutting height, a clogged discharge channel or housing, and a dull or damaged blade.
Try: Adjust the deck, clean the discharge path while unplugged, and replace or professionally resharpen the blade if needed.
The grass bag does not fill properly
Check: Wet grass, cutting height, a clogged bag grille, and a blocked discharge channel or housing.
Try: Let the lawn dry, correct the height, and clean the bag grille and discharge path while the mower is unplugged.
Replacement Accessories
| Accessory | Model |
|---|---|
| 20-inch mower blade | MJ408E-BLD |
| 14.5-gallon grass collection bag | MJ408E-BAG |
| Side-discharge chute | MJ408E-39 |
| Mulching plug | MJ408E-MULCHPG |
| SJTW-A 14-gauge, 50-foot extension cord with lighted end | PJEXT50-B |
Official Video
Frequently Asked Questions
What comes with the MJ408E?
It includes the mower, upper and lower handles and their mounting hardware, grass bag, side-discharge chute, mulching plug, operator’s manual, and registration card.
Is the MJ408E gas-powered or electric?
It is a 12-amp corded electric mower. It does not require gasoline, oil, a pull cord, or engine tune-ups.
What lawn size is it designed for?
It is intended for small to medium-sized residential lawns.
Can it bag, mulch, and side discharge?
Yes. Configure only one cutting mode at a time and install only the components required for that mode.
Which extension cord should I use?
Use an outdoor-rated 14 AWG cord up to 50 ft. or a 12 AWG cord from 50–100 ft. Never exceed 100 ft.
Can I mow wet grass?
No. Do not use the mower in rain or on damp or wet grass.
What cutting heights are available?
Seven positions provide cutting heights from 1.96 to 4.13 inches (50–105 mm).
Why should I start on short grass?
Tall grass can overload the motor during startup. Begin on level, short grass or an already-cut area, then move into the section to be mowed.
Which replacement blade fits?
Use replacement blade MJ408E-BLD.
What warranty applies?
The MJ408E includes a 2-year limited warranty. Coverage is subject to the complete warranty terms and proof-of-purchase requirements.