Murray MP550RMD21 Lawn Mower Manual

The Murray MP550RMD21 is a 21-inch, 5.5 HP Briggs & Stratton-powered push lawn mower with rear bagging, side discharge, and mulching capabilities. It features a durable steel deck, 6-position single-lever height adjustment, easy-start engine, and a 2.5-bushel grass 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 Operation 6. Cutting Height Adjustment 7. Bagging & Discharge Options 8. Safety Features 9. Maintenance & Storage 10. Warranty Information 11. Troubleshooting

Features at a Glance

Key components: 5.5 HP Briggs & Stratton engine, 21-inch steel cutting deck, rear grass bag, side discharge chute, mulching plug, single-lever height adjustment, and recoil start system.

Feature	Description
Engine	5.5 HP Briggs & Stratton 4-cycle gasoline engine
Cutting Width	21-inch steel deck
Cutting Options	Rear bagging, side discharge, mulching
Height Adjustment	Single-lever, 6 positions (1.0" to 3.5")
Grass Bag	2.5-bushel capacity, easy-empty design
Start System	Recoil pull-start
Wheels	8-inch rear, 7-inch front
Handle	Folding, adjustable height
Safety Features	Blade control bail, engine stop lever
Fuel Tank	1-quart capacity

Assembly Instructions

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

Attach handle: Secure upper and lower handle sections with provided bolts.
Install wheels: Slide wheels onto axles; secure with washers and retaining clips.
Attach grass bag: Hook bag onto rear deck brackets; ensure secure fit.
Install side discharge chute: Attach to deck opening with wing nut.
Add mulching plug: Insert into deck opening when mulching.
Check oil: Verify engine oil level before first use.

WARNING! Wear gloves during assembly. Ensure all bolts are tightened securely.

First-Time Setup

Prepare mower for initial use.

Add oil: Fill with SAE 30 detergent oil (check dipstick).
Add fuel: Use fresh unleaded gasoline (no ethanol recommended).
Adjust handle height: Set to comfortable operating position.
Set cutting height: Use single lever to select desired height.
Test controls: Practice engaging blade control bail and engine stop.

CAUTION! Perform setup outdoors. Keep fuel away from ignition sources.

Specifications

Engine: 5.5 HP Briggs & Stratton, 4-cycle, single cylinder.
Cutting Width: 21 inches.
Cutting Height: 6 positions: 1.0", 1.5", 2.0", 2.5", 3.0", 3.5".
Deck Material: Powder-coated steel.
Grass Bag Capacity: 2.5 bushels.
Wheels: 8-inch rear, 7-inch front.
Weight: Approximately 55 lbs.
Fuel Type: Unleaded gasoline (minimum 87 octane).
Oil Type: SAE 30 detergent oil (20 oz capacity).

Controls and Operation

Primary controls: Blade control bail, engine stop lever, throttle control, recoil starter.

Starting Procedure:

Check oil and fuel levels.
Move throttle to FAST position.
Prime engine (if equipped) by pressing primer bulb 3 times.
Pull recoil starter cord firmly.
Engage blade control bail to start cutting.

Stopping: Release blade control bail; move throttle to STOP; wait for blade to stop completely.

Cutting Height Adjustment

Use single lever to adjust all four wheels simultaneously.

Stop engine and wait for blade to stop.
Pull height adjustment lever outward.
Move lever to desired position (1-6).
Release lever to lock in position.

Tip: For first cut of season, set to highest position; gradually lower for subsequent mows.

Bagging & Discharge Options

Three cutting modes available:

Rear Bagging: Attach grass bag; ideal for collecting clippings.
Side Discharge: Install discharge chute; suitable for tall grass.
Mulching: Install mulching plug; returns clippings to lawn as fertilizer.

WARNING! Always stop engine before changing cutting modes. Ensure attachments are secure.

Safety Features

Blade control bail: Must be held to keep blade rotating. Engine stop lever: Cuts ignition. Safety labels: Read and follow all warnings. Protective shield: Covers discharge opening.

Maintenance & Storage

Regular maintenance ensures optimal performance.

After each use: Clean underside of deck; check for damage.
Monthly: Check oil level; inspect air filter; sharpen blade.
Seasonal: Change oil; replace spark plug; clean fuel system.
Storage: Drain fuel or add stabilizer; store in dry place.

CAUTION! Disconnect spark plug wire before performing maintenance.

Warranty Information

Limited 2-year warranty on mower; 90-day warranty on engine. Warranty covers defects in materials/workmanship. Not covered: Normal wear, misuse, improper maintenance. For warranty claims, contact Murray customer service at 1-800-800-7310 or visit www.murray.com. Keep original receipt as proof of purchase.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No fuel/spark	Check fuel level; ensure spark plug wire connected; prime engine.
Poor cutting performance	Dull blade	Sharpen or replace blade; check cutting height.
Engine runs rough	Dirty air filter	Clean or replace air filter; check fuel quality.
Vibration	Loose blade	Tighten blade bolt; check for bent blade.
Bag not filling	Clogged deck	Clean underside of deck; check grass height.

Service: For repairs, contact authorized service center. Use only genuine Murray parts.

Support: 1-800-800-7310; www.murray.com