Murray 405628x51A Lawn Mower Manual

The Murray 405628x51A is a 20-inch push lawn mower featuring a Briggs & Stratton 550 Series 140cc gasoline engine, 3-in-1 mulching/bagging/side discharge capability, single-lever height adjustment for all four wheels, durable steel deck, easy-start system, and a 2.1 bushel rear bag. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Assembly Instructions 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Operating the Mower 7. Maintenance Schedule 8. Storage Instructions 9. Safety Information 10. Warranty & Support 11. Troubleshooting

Features at a Glance

Key components: Briggs & Stratton 140cc engine, 20-inch steel cutting deck, rear grass bag, height adjustment lever, recoil starter, and safety handle.

FeatureDescription
EngineBriggs & Stratton 550 Series, 140cc, 4-cycle
Cutting Width20 inches
Cutting OptionsMulch, Bag, Side Discharge
Height AdjustmentSingle lever, 6 positions (1.5-3.75 inches)
StarterRecoil (pull-start)
Deck MaterialDurable steel
Grass Bag Capacity2.1 bushels
Wheels8-inch rear, 7-inch front
HandleFoldable, with safety bail
Fuel Tank Capacity0.5 gallons

Assembly Instructions

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

  1. Attach the handle: Align lower handle sections with deck brackets, secure with bolts and wing nuts.
  2. Install the upper handle: Connect to lower handle, secure with provided hardware.
  3. Attach the grass bag: Hook bag frame onto rear deck brackets; ensure it clicks into place.
  4. Install the side discharge chute (if not mulching): Attach to deck opening with wing nut.
  5. Check wheel installation: Ensure all wheels are securely fastened and rotate freely.

WARNING! Do not add fuel or attempt to start engine during assembly. Keep hands clear of cutting blade.

First-Time Setup

Before first use, complete these steps.

  1. Add engine oil: Use SAE 30 detergent oil (approx. 20 oz). Check dipstick.
  2. Add fuel: Use fresh unleaded gasoline (87 octane minimum). Do not overfill.
  3. Check tire pressure: Inflate to 15 PSI (if applicable).
  4. Adjust cutting height: Set lever to desired position (start at 3 inches for first mow).
  5. Test safety features: Ensure engine stops when bail handle is released.

CAUTION! Always use fuel stabilizer if storing over 30 days. Never use E85 or diesel fuel.

Specifications

Controls and Settings

Primary controls located on handle and engine.

Handle: Safety bail (must be held to run engine), height adjustment lever, fold latch.

Engine: Throttle control (FAST/SLOW/STOP), primer bulb (3 presses for cold start), choke lever, recoil starter grip.

Deck: Mulch plug (for mulching), bag attachment hooks, side discharge chute.

Height Adjustment: Single lever controls all four wheels. Positions: 1 (lowest) to 6 (highest).

Operating the Mower

Starting, mowing, and stopping procedures.

  1. Check oil and fuel levels before each use.
  2. Set cutting height appropriate for grass condition.
  3. Starting: Set throttle to FAST, press primer bulb 3 times, pull recoil starter firmly.
  4. Engage blade: Hold safety bail against handle.
  5. Mowing: Push mower at steady pace; overlap passes slightly.
  6. Stopping: Release safety bail to stop blade; set throttle to STOP.
  7. Empty bag: Stop engine, wait for blade to stop, remove and empty bag.

Tip: Mow when grass is dry for best results. Avoid mowing in reverse.

Maintenance Schedule

Regular maintenance ensures optimal performance and longevity.

IntervalTask
Before each useCheck oil level, inspect blade for damage, clear deck of debris
Every 25 hoursChange engine oil, check air filter, inspect spark plug
Every seasonSharpen or replace blade, clean underside of deck, lubricate wheels
As neededReplace air filter, spark plug, check tire pressure

Blade Sharpening: Disconnect spark plug wire. Remove blade, sharpen at 30-degree angle, balance before reinstalling.

Storage Instructions

Proper storage prevents fuel system issues and corrosion.

  1. Run engine to burn remaining fuel in carburetor OR add fuel stabilizer to tank.
  2. Change oil at end of season.
  3. Clean underside of deck thoroughly.
  4. Remove spark plug, add 1 teaspoon of oil to cylinder, pull starter slowly to coat.
  5. Store in dry, covered area. Fold handle to save space.

CAUTION! Never store mower with fuel in tank for more than 30 days without stabilizer.

Safety Information

Read and follow all safety instructions to prevent injury.

DANGER! The rotating blade can cause severe injury. Always ensure engine and blade have completely stopped before approaching deck.

Warranty & Support

Murray mowers are backed by a limited warranty. For residential use, the engine is covered by Briggs & Stratton's warranty terms. The mower deck and components have a 2-year limited warranty against defects in materials or workmanship.

To make a warranty claim or for technical support:

Copyright © Murray LLC. Murray is a trademark of Briggs & Stratton Power Products Group, LLC.

Troubleshooting

SymptomPossible CauseCorrective Action
Engine won't startNo fuel, old fuel, clogged air filter, spark plug issueCheck fuel level, use fresh gas, clean/replace air filter, check spark plug.
Engine runs poorlyDirty air filter, old fuel, clogged carburetorClean air filter, drain old fuel, consider carburetor cleaner.
Uneven cuttingDull blade, uneven tire pressure, deck cloggedSharpen blade, inflate tires evenly, clean deck underside.
VibrationLoose blade, bent blade, debris stuckStop engine, disconnect spark plug, tighten or replace blade.
Bag not fillingWet grass, deck clogged, engine speed too lowMow dry grass, clean deck, run engine at FAST setting.

For Service: 1-800-800-7310; www.murray.com

Murray 405628x51A Lawn Mower Manual © - All Rights Reserved 2025