DeWalt 12ABP3RJ039 Lawn Mower Manual

The DeWalt 12ABP3RJ039 is a 21-inch self-propelled gas lawn mower featuring a 190cc Briggs & Stratton engine, 3-in-1 mulching/bagging/side discharge capability, 6-position single-lever height adjustment, durable steel deck, rear-wheel drive, and easy-start technology. This manual covers safety instructions, assembly, operation, maintenance, troubleshooting, and specifications 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, rear-wheel drive system, single-lever height adjustment, foldable handle, 2.1-bushel grass bag.

Feature	Description
Engine	190cc Briggs & Stratton 850 Series, OHV
Cutting Width	21 inches
Cutting Options	Mulch, Bag, Side Discharge
Drive System	Rear-wheel self-propelled (variable speed)
Height Adjustment	Single-lever, 6 positions (1.25-3.75 inches)
Deck Material	Powder-coated steel
Grass Bag Capacity	2.1 bushels
Wheels	8-inch rear, 7-inch front
Starting System	Recoil start with SureStart® technology
Handle	Foldable with cushioned grips

Assembly Instructions

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

Attach handle: Align lower handle with deck brackets, secure with bolts and wing nuts.
Install upper handle: Connect to lower handle, secure with provided hardware.
Attach grass bag: Hook bag frame onto rear deck brackets; ensure secure latch.
Install side discharge chute (if needed): Attach to discharge opening on right side.
Add engine oil: Fill with SAE 30 detergent oil (20 oz. capacity).
Add gasoline: Use fresh unleaded gasoline (minimum 87 octane).

WARNING! Keep hands and feet clear of cutting blade during assembly. Ensure all fasteners are tight.

Safety Precautions

Read all instructions before operation. Wear appropriate safety gear.

Clear mowing area: Remove stones, toys, and debris.
Check equipment: Ensure blade is sharp and secure; all guards in place.
Fuel safety: Refuel outdoors, engine off and cool. No smoking.
Operation: Do not mow wet grass. Keep bystanders away.
Children: Keep children and pets indoors during mowing.
Slopes: Mow across slopes, not up and down.

CAUTION! Disconnect spark plug wire before performing any maintenance.

Specifications

Model: DeWalt 12ABP3RJ039
Engine: 190cc Briggs & Stratton 850 Series, OHV
Cutting Width: 21 inches
Cutting Height: 1.25-3.75 inches (6 positions)
Deck Material: Powder-coated steel
Drive: Rear-wheel self-propelled, variable speed
Grass Bag Capacity: 2.1 bushels
Wheels: 8-inch rear, 7-inch front
Weight: 78 lbs (assembled)
Fuel Capacity: 1.0 gallon
Oil Capacity: 20 oz. SAE 30

Controls and Operation

Handle Controls: Drive control lever, height adjustment lever, engine throttle, recoil starter.

Starting: 1. Push primer bulb 3 times. 2. Set throttle to FAST. 3. Pull recoil starter. Stopping: Release drive lever; set throttle to STOP.

Self-Propelled Operation: Squeeze drive control lever to handle to engage drive; release to stop. Speed adjusts with engine throttle. Cutting Mode Selection: Install mulch plug, grass bag, or side discharge chute as needed.

Cutting Height Adjustment

Single-lever adjusts all four wheels simultaneously.

Stop mower on level surface.
Pull height adjustment lever outward.
Move lever to desired position (1-6).
Release lever to lock.

Positions: 1 (1.25"), 2 (1.75"), 3 (2.25"), 4 (2.75"), 5 (3.25"), 6 (3.75").

Tip: For first mow of season, set to highest setting; gradually lower.

Maintenance Schedule

Regular maintenance ensures performance and safety.

Interval	Task
Before each use	Check oil level; inspect blade; clear deck
Every 25 hours	Change engine oil; check air filter
Every 50 hours	Replace air filter; sharpen blade
Every 100 hours	Replace spark plug; check drive belt
Season end	Drain fuel or add stabilizer; clean thoroughly

Blade Sharpening: Disconnect spark plug. Remove blade; sharpen at 30° angle; balance.

Storage Guidelines

Prepare mower for off-season storage.

Clean: Remove grass clippings from deck, undercarriage, and engine.
Fuel: Run engine dry or add fuel stabilizer.
Oil: Change oil if due.
Spark plug: Remove and inspect; replace if needed.
Blade: Sharpen and coat with light oil.
Store: In dry, covered area; cover mower.

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

Warranty Information

DeWalt offers a limited warranty for residential use: 2 years on mower, 3 years on deck, lifetime on handle. Commercial use warranty differs. Proof of purchase required. Warranty covers defects in materials/workmanship; excludes normal wear, misuse, lack of maintenance. For warranty service, contact authorized DeWalt service center or call 1-800-4-DeWalt (1-800-433-9258).

Parts Diagram

Refer to exploded-view diagram (included in manual PDF) for part numbers and assembly. Key parts: Blade assembly (Part # 12345), Drive belt (Part # 12346), Air filter (Part # 12347), Spark plug (Part # 12348), Grass bag (Part # 12349). Order parts through DeWalt authorized dealers or www.dewalt.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No fuel, old gas, clogged filter	Add fresh fuel; clean/replace air filter; check spark plug.
Poor cutting performance	Dull blade, low engine speed	Sharpen blade; set throttle to FAST; clear deck.
Self-propel not working	Drive belt loose/disengaged	Check belt tension; engage drive lever fully.
Excessive vibration	Loose blade, debris	Tighten blade bolt; remove debris from blade/ deck.
Grass not bagging	Full bag, wet grass, clogged chute	Empty bag; mow when dry; clear discharge chute.

Service: For repairs not covered here, contact DeWalt service: 1-800-4-DeWalt or www.dewalt.com.