Murray 405021x51A Lawn Mower Manual

The Murray 405021x51A is a 21-inch push lawn mower featuring a Briggs & Stratton engine, 3-in-1 mulching/bagging/side discharge capability, single-lever height adjustment, easy-start system, durable steel deck, and rear-wheel drive. This manual covers safety, assembly, operation, maintenance, troubleshooting, and specifications to ensure proper and safe use.

1. Features at a Glance 2. Assembly Instructions 3. Safety Precautions 4. Specifications 5. Controls and Operation 6. Cutting Height Adjustment 7. Maintenance Schedule 8. Engine Care 9. Storage Instructions 10. Warranty Information 11. Troubleshooting

Features at a Glance

Key components: 21-inch steel cutting deck, Briggs & Stratton engine, rear bagger, mulching plug, side discharge chute, single-lever height adjustment, and push handle with safety bail.

Feature	Description
Cutting Width	21 inches
Engine	Briggs & Stratton 140cc
Cutting Options	3-in-1 (Mulch, Bag, Side Discharge)
Height Adjustment	Single lever, 6 positions (1.5-3.5 inches)
Drive System	Rear-wheel push
Deck Material	Powder-coated steel
Starter	Recoil easy-start
Wheels	8-inch rear, 7-inch front
Weight	Approx. 55 lbs
Fuel Tank	0.5 gallon capacity

Assembly Instructions

Unpack all parts and inspect for damage. Assembly requires basic tools (included).

Attach handle: Align lower handle with deck brackets, secure with provided bolts and wing nuts.
Install upper handle: Connect to lower handle, tighten knobs.
Attach grass bag: Hook bag frame onto rear deck brackets.
Install side discharge chute: Snap into place on right side of deck.
Insert mulching plug: Place into rear discharge opening when mulching.
Check wheel alignment: Ensure all wheels are securely attached and rotate freely.

WARNING! Wear gloves during assembly. Keep hands clear of sharp edges.

Safety Precautions

Always follow safety guidelines to prevent injury.

Read manual thoroughly before operation.
Clear mowing area of debris, stones, and toys.
Wear sturdy shoes, eye protection, and long pants.
Do not operate on slopes greater than 15 degrees.
Never leave mower unattended with engine running.
Keep hands and feet away from moving parts.
Stop engine before adjusting height or unclogging deck.
Use only in daylight or good artificial light.

DANGER! Gasoline is flammable. Refuel outdoors with engine off and cool.

Specifications

Model: Murray 405021x51A
Cutting Width: 21 inches
Engine: Briggs & Stratton 140cc, 4-cycle
Fuel Type: Unleaded gasoline (87 octane or higher)
Oil Type: SAE 30 detergent motor oil
Oil Capacity: 20 oz (0.6 L)
Cutting Heights: 6 positions, 1.5" to 3.5"
Bag Capacity: 2.0 bushels
Warranty: 2-year limited

Controls and Operation

Handle includes safety bail (deadman control) and throttle control.

Starting: 1. Check oil and fuel levels. 2. Push primer bulb 3 times. 3. Set throttle to FAST. 4. Pull recoil starter firmly.

Stopping: Release safety bail to stop blade. Move throttle to STOP position.

Mowing Tips: Mow when grass is dry. Overlap passes by 2 inches. Change mowing pattern weekly.

Cutting Height Adjustment

Single lever adjusts all four wheels simultaneously.

Stop engine and wait for blade to stop completely.
Pull height adjustment lever outward.
Move lever to desired height setting (1-6).
Release lever to lock in position.
Check that all wheels are at same height.

Recommended: Cut no more than 1/3 of grass height at one time.

Maintenance Schedule

Maintenance	Frequency
Check oil level	Before each use
Clean underside of deck	After each use
Check blade sharpness	Every 25 hours
Change oil	First 5 hours, then every 50 hours
Replace air filter	Every 100 hours
Replace spark plug	Every 100 hours
Lubricate wheels	Every season
Check bolts and nuts	Monthly

Engine Care

Briggs & Stratton engine requires regular maintenance.

Oil Change: Run engine 2-3 minutes to warm oil. Drain via dipstick tube. Refill with SAE 30.
Air Filter: Remove foam pre-cleaner, wash in soapy water, squeeze dry. Replace paper element if dirty.
Spark Plug: Clean with wire brush, gap at 0.030 inches. Replace if electrodes are worn.
Fuel System: Use fresh gasoline. Add fuel stabilizer for storage over 30 days.

CAUTION! Disconnect spark plug wire before performing any maintenance.

Storage Instructions

Proper storage extends mower life.

Drain or stabilize fuel: Run engine dry or add fuel stabilizer.
Change oil: Fresh oil prevents corrosion.
Clean thoroughly: Remove grass clippings from deck and wheels.
Sharpen blade: Sharp blade ready for next season.
Store indoors: In dry, covered area away from moisture.
Remove spark plug: Add 1 tablespoon of oil to cylinder, pull starter slowly to coat.

WARNING! Never store mower with fuel in tank near open flame or heat source.

Warranty Information

Murray 405021x51A includes 2-year limited warranty covering defects in materials/workmanship. Warranty does not cover normal wear, improper maintenance, or commercial use. Keep original receipt for warranty claims. For service, contact Murray customer service at 1-800-800-7310 or visit www.murray.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No fuel, old gas, clogged filter	Check fuel level; use fresh gas; clean/replace air filter.
Engine runs poorly	Dirty spark plug, bad fuel	Clean/replace spark plug; drain old fuel.
Uneven cutting	Dull blade, uneven height	Sharpen blade; adjust cutting height evenly.
Vibration	Bent blade, loose parts	Inspect blade for damage; tighten all bolts.
Won't mulch properly	Wet grass, dull blade	Mow when dry; sharpen blade; slow mowing speed.
Bag not filling	Clogged deck, high grass	Clean underside of deck; mow more frequently.

Service: For repairs, use authorized Murray service centers. Always use genuine Murray parts.