Murray 405001x78B Lawn Mower Manual

The Murray 405001x78B is a 21-inch push lawn mower featuring a 190cc Briggs & Stratton engine, 3-in-1 mulching/bagging/side discharge capability, single-lever height adjustment (1.5-4 inches), durable steel deck, easy-start system, washout port for cleaning, and large rear wheels for maneuverability. This manual covers safety instructions, assembly, operation, maintenance, troubleshooting, and storage guidelines for optimal performance and longevity.

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. Storage Guidelines 9. Warranty Information 10. Parts Diagram 11. Troubleshooting

Features at a Glance

Key components: 190cc Briggs & Stratton engine, 21-inch steel cutting deck, 3-in-1 function, single-lever height adjustment, washout port, rear-wheel drive.

Feature	Description
Engine	190cc Briggs & Stratton 4-cycle engine
Cutting Width	21-inch steel deck
Cutting Options	Mulch, Bag, Side Discharge (3-in-1)
Height Adjustment	Single-lever, 6 positions (1.5-4 inches)
Drive System	Rear-wheel drive with large wheels
Starting System	Recoil easy-start
Deck Wash Port	Connect garden hose for easy cleaning
Fuel Tank	0.95-gallon capacity
Grass Bag	2.1 bushel capacity
Warranty	2-year limited warranty

Assembly Instructions

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

Attach handle: Insert lower handle into deck brackets, secure with 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 (if not mulching): Snap into place on right side.
Add engine oil: Use SAE 30 detergent oil (20 oz. capacity).
Add gasoline: Use fresh unleaded gasoline (87 octane minimum).

WARNING! Do not add gasoline during assembly. Keep away from sparks or flames.

Safety Precautions

Always follow safety guidelines to prevent injury or damage.

Read manual thoroughly before operation.
Clear mowing area of stones, toys, and debris.
Wear sturdy shoes, long pants, and eye protection.
Never mow wet grass or in poor visibility.
Keep children and pets away from mowing area.
Disconnect spark plug before performing maintenance.
Never leave mower unattended while engine is running.
Use extreme caution on slopes; mow across, not up and down.

DANGER! Rotating blade can cause severe injury. Keep hands and feet away.

Specifications

Model: Murray 405001x78B
Engine: 190cc Briggs & Stratton 4-cycle
Cutting Width: 21 inches
Cutting Height: 1.5 to 4 inches (6 positions)
Deck Material: Powder-coated steel
Wheels: 8-inch rear, 7-inch front
Fuel Capacity: 0.95 gallons
Oil Capacity: 20 oz. SAE 30
Weight: 65 lbs (approx.)
Warranty: 2-year limited

Controls and Operation

Handle Controls: Drive control bar (must be held to move), height adjustment lever, engine control (stop/start).

Starting Engine: 1. Push primer bulb 3 times (cold engine). 2. Set throttle to FAST position. 3. Pull recoil starter firmly.

Stopping Engine: Release drive control bar, move throttle to STOP position.

Operating: Hold drive control bar to engage drive wheels. Release to stop movement. Adjust speed with throttle.

Cutting Height Adjustment

Single-lever adjustment for all four wheels simultaneously.

Stop engine and wait for blade to stop completely.
Pull height adjustment lever outward.
Move lever to desired position (1-6, lowest to highest).
Release lever to lock in position.
Test mower stability on flat surface before mowing.

Tip: For first mow of season, set to highest position. Gradually lower for subsequent mows.

Maintenance Schedule

Regular maintenance ensures optimal performance and extends mower life.

Maintenance Task	Frequency
Check engine oil level	Before each use
Clean under deck	After each use
Check blade sharpness	Every 25 hours
Replace air filter	Every season or 50 hours
Change engine oil	First 5 hours, then every 50 hours
Replace spark plug	Every 100 hours
Lubricate wheels	Every season
Check drive belt	Every 50 hours

Note: Always disconnect spark plug before performing maintenance.

Storage Guidelines

Proper storage prevents fuel system issues and corrosion.

Run engine to use remaining fuel, or add fuel stabilizer.
Change engine oil at end of season.
Clean entire mower thoroughly, especially under deck.
Remove spark plug, add 1 oz. oil to cylinder, pull starter slowly.
Store in clean, dry place, protected from elements.
Cover mower to prevent dust accumulation.

CAUTION! Never store mower with gasoline in tank indoors or near open flame.

Warranty Information

Murray 405001x78B comes with 2-year limited warranty covering defects in materials/workmanship. Warranty does not cover normal wear, misuse, improper maintenance, or commercial use. Keep original receipt as proof of purchase. For warranty service, contact authorized Murray service center at 1-800-800-7310 or visit www.murray.com.

Parts Diagram

Refer to diagram for replacement parts identification and ordering.

Key Parts: 1. Cutting blade, 2. Drive belt, 3. Air filter, 4. Spark plug, 5. Wheels, 6. Height adjustment lever, 7. Grass bag, 8. Side discharge chute, 9. Primer bulb, 10. Recoil starter.

Ordering: Use model number 405001x78B when ordering parts. Genuine Murray parts ensure proper fit and performance.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No fuel, old gasoline, clogged air filter	Add fresh gasoline; clean/replace air filter; check spark plug.
Engine runs poorly	Dirty air filter, old gasoline	Replace air filter; drain and refill with fresh gasoline.
Uneven cutting	Dull blade, uneven tire pressure	Sharpen or replace blade; check tire pressure.
Mower vibrates excessively	Loose blade, damaged blade	Tighten blade bolt; replace damaged blade.
Won't drive	Drive belt worn or broken	Inspect and replace drive belt if necessary.
Grass not discharging	Wet grass, clogged deck	Clean under deck; mow when grass is dry.

Service: For technical support, call 1-800-800-7310 or visit www.murray.com.