Murray MX450 Lawn Mower Manual

The Murray MX450 is a 21-inch, 3-in-1 push lawn mower featuring a 450cc Briggs & Stratton engine, rear bagging, side discharge, and mulching capabilities. It includes a single-lever height adjustment system (1.5 to 4 inches), durable steel deck, easy-start system, and ergonomic handle with soft-grip. This manual covers safety, assembly, operation, maintenance, troubleshooting, and specifications. Always read and follow all safety instructions before use.

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

Features at a Glance

Key components: 450cc Briggs & Stratton engine, 21-inch steel cutting deck, 3-in-1 functionality (Bag/Mulch/Side Discharge), single-lever height adjustment, rear grass bag, ergonomic handle, and easy-start system.

Feature	Description
Engine	450cc Briggs & Stratton, 4-cycle, OHV
Cutting Width	21 inches
Cutting Height	1.5 to 4 inches (6 positions)
Deck Material	Powder-coated steel
Drive System	Push (manual)
Collection Capacity	2.0 bushel rear bag
Wheels	8-inch rear, 7-inch front
Starting System	Recoil with primer bulb
Weight	Approx. 65 lbs
Fuel Tank Capacity	0.5 gallon

Assembly Instructions

Unpack all parts from the box. Assembly requires basic tools (included: wrench, screwdriver).

Attach the handle: Align lower handle with deck brackets, secure with provided bolts and wing nuts.
Install the grass bag: Attach bag support frame to rear deck hooks, then clip bag onto frame.
Attach the side discharge chute (if not pre-installed): Slide into side port and secure with pin.
Install the mulching plug (if using): Insert into rear discharge opening.
Add engine oil: Use SAE 30 (approx. 20 oz) – check dipstick for proper level.
Add fuel: Use fresh unleaded gasoline (87 octane or higher). Do not overfill.

WARNING! Never add fuel while engine is hot or running. Ensure all fasteners are tight before operation.

Safety Information

Always wear sturdy shoes and eye protection. Keep bystanders, especially children and pets, away from the area.

Read the manual thoroughly before starting.
Clear mowing area of sticks, stones, and debris.
Check that all guards and shields are in place.
Never operate without the grass bag or discharge chute properly attached (unless mulching plug is installed).
Stop engine and wait for all moving parts to stop before unclogging, adjusting, or performing maintenance.
Do not mow on steep slopes (over 15 degrees). Mow across slopes, not up and down.
Refuel outdoors only, before starting, with engine cool.

DANGER! Keep hands and feet away from rotating blades. Never lift or carry mower while engine is running.

Specifications

Model: Murray MX450
Engine: Briggs & Stratton 450cc, 4-cycle, OHV
Cutting Width: 21 inches
Cutting Height Range: 1.5" - 4" (6 positions)
Deck: 21-inch steel, powder-coated
Wheels: 8" rear, 7" front
Bag Capacity: 2.0 bushels
Fuel Type: Unleaded gasoline (87 octane min)
Oil Type: SAE 30 (summer), check manual for alternatives
Weight: Approx. 65 lbs
Warranty: 2-year limited (see warranty card)

Controls and Operation

Handle Controls: Throttle lever (FAST/SLOW/STOP), Recoil starter grip, Primer bulb, Blade control (bail) lever.

Starting Procedure:

Check oil and fuel levels.
Press primer bulb 3 times (cold engine).
Set throttle to FAST position.
Pull blade control lever back to handle and hold.
Pull starter grip firmly until engine starts.
Release blade control lever to stop blade; engine continues running.

Stopping: Release blade control lever, then move throttle to STOP. For emergency stop, release blade control lever immediately.

Cutting Height Adjustment

Single-lever adjustment: Move lever to one of 6 positions (1=lowest, 6=highest). Adjust all wheels simultaneously.

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

Tip: For first mow of season or very tall grass, use a higher setting, then lower for subsequent mows.

Maintenance Schedule

Regular maintenance ensures long life and safe operation.

Task	Frequency
Check engine oil level	Before each use
Clean underside of deck	After each use (cooled)
Check blade for sharpness/damage	Every 25 hours
Replace air filter	Every season or 25 hours
Change engine oil	First 5 hours, then every 50 hours or season
Replace spark plug	Every 100 hours or season
Lubricate wheel axles & height adjuster	Every 25 hours
Inspect drive belt (if equipped)	Every 50 hours

CAUTION! Always disconnect spark plug wire before performing any maintenance involving the blade or underside of deck.

Storage Guidelines

Prepare mower for storage if not used for 30 days or more.

Run engine to burn off remaining fuel in carburetor, or add fuel stabilizer to fresh gas and run for 5 minutes.
Change engine oil (end of season).
Clean deck thoroughly, dry, and apply light oil to prevent rust.
Remove spark plug, add 1 tablespoon of oil into cylinder, pull starter cord slowly to coat, reinstall plug.
Store in a clean, dry place, covered.

WARNING! Gasoline is flammable. Store mower and fuel away from open flame, pilot lights, and heat sources.

Warranty Information

Murray MX450 is covered by a 2-year limited warranty for residential use from date of purchase. Warranty covers defects in materials or workmanship. It does not cover normal wear, misuse, lack of maintenance, or commercial use. Proof of purchase is required. For warranty service, contact an authorized Murray service center. For details, see the separate warranty card included in the box or visit www.murray.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No fuel, old fuel, clogged air filter, spark plug fault	Add fresh fuel; clean/replace air filter; check/replace spark plug; ensure primer bulb pressed.
Engine runs poorly or stalls	Dirty air filter, old gasoline, clogged fuel line	Replace air filter; drain and refill with fresh gas; check fuel line for obstructions.
Uneven cutting	Dull or bent blade, uneven tire pressure, deck clogged	Sharpen or replace blade; clean deck; check tire pressure/wheel height.
Excessive vibration	Loose blade, bent blade, debris stuck in blade	Stop engine, disconnect spark plug, tighten blade bolt (58-70 ft-lbs) or replace blade.
Grass not discharging/bagging	Wet grass, deck clogged, engine speed too low, dull blade	Mow when grass is dry; clean deck; run at FAST throttle; sharpen blade.
Wheels hard to turn	Axles need lubrication, debris around axles	Clean axles and apply light oil or grease.

For Service: Contact authorized Murray service center or call 1-800-XXX-XXXX. Have model number (MX450) and serial number ready.