MTD
Gas Walk-Behind Mower

Model #12AE999P099 Official MTD lawn mower

Here are the diagrams and repair parts for MTD 12AE999P099 lawn mower, as well as links to manuals and error code tables, if available.

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Owner’s manual

Showing 10 of 257 parts

Free Shipping Lawn Mower 21-in Deck Mulching Blade (replaces 01002810, 742-0741A, 942-04276, 942-0741)#34

Handle/deck/chute Diagram

In Stock
$20.68 | 
33% OFF 
MSRP: $31.00
Lawn & Garden Equipment Lock Nut, 5/16-18 (replaces 753-05591)

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Lawn & garden equipment lock nut, 5/16-18 (replaces 753-05591)

Part #712-04063
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$3.62 | 
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MSRP: $4.90
Lawn Mower Blade Support (replaces 936-0524A)#32

Handle/deck/chute Diagram

Lawn mower blade support (replaces 936-0524a)

Part #736-0524B
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Lawn & Garden Equipment Nut#66

Handle/deck/chute Diagram

Lawn & garden equipment nut

Part #712-04064
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$3.05 | 
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MSRP: $5.00
Lawn Mower Battery Charger (replaces 725-06121A)#73

Handle/deck/chute Diagram

Walk-behind lawn mower battery charger

Part #725-04329
Replaced by #725-06121B
?
Manufacturer substitution
This part replaces 725-04329. Substitute parts can look different from the original.
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$39.36 | 
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MSRP: $50.00
Lawn Tractor Screw, 1/4-20 x 5/8-in (replaces 910-1652)

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Lawn tractor screw, 1/4-20 x 5/8-in (replaces 910-1652)

Part #710-1652
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Lawn Mower Roller Wheel#60

Handle/deck/chute Diagram

Lawn mower roller wheel

Part #756-0625
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Lawn Mower Ground Drive Belt (replaces 754-0460)#37

Handle/deck/chute Diagram

Lawn mower ground drive belt (replaces 754-0460)

Part #954-0460
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Lawn & Garden Equipment Hex Cap Screw#14

Drive Diagram

Lawn & garden equipment hex cap screw

Part #710-0751
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Lawn & Garden Equipment Cotter Pin

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Lawn & garden equipment cotter pin

Part #914-0104
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Symptoms for gas walk-behind mowers

Choose a symptom to see related walk-behind mower repairs.

Main causes: uneven wheel height settings, damaged wheel, dull or damaged cutting blade
Main causes: damaged cutting blade, loose cutting blade, damaged flywheel key, engine needs tune up
Main causes: engine needs tune up, dirty or clogged carburetor, damaged flywheel key
Main causes: dirty carburetor, bad spark plug, clogged air filter, engine choke problems, clogged gas cap vent
Main causes: drive control cable failure, worn or broken drive belt, bad transmission, broken drive wheel
Main causes: stale gas, engine needs tune up, bad spark plug, dead battery, bad recoil starter, faulty safety switch, bad ignition coil

Repair guides for gas walk-behind mowers

These step-by-step repair guides will help you safely fix what’s broken on your walk-behind lawn mower.

How to replace a lawn mower spark plug

Take a few minutes to replace the spark plug during your lawn mower's annual tune-up or if the spark plug is burnt or cracked.

Repair difficulty
Time required
 15 minutes or less
How to replace a lawn mower blade

Check your lawn mower blade regularly and replaced it if it's bent or damaged.

Repair difficulty
Time required
 15 minutes or less
How to replace a lawn mower flywheel key on a flathead engine

When you hit a hard object with your mower, the flywheel can shear to protect more expensive components. Learn how to replace this tiny but essential part.

Repair difficulty
Time required
 45 minutes or less

Articles and videos common to all walk-behind mowers

Use the advice and tips in these articles and videos to get the most out of your walk-behind lawn mower.

February 11, 2023

Top 10 electric lawn and garden tools for 2023

Top 10 electric lawn and garden tools for 2023

Learn about the top 10 must-have electric lawn & garden tools for 2023

August 30, 2022

How to enjoy all the online benefits we offer on our Sears PartsDirect website

How to enjoy all the online benefits we offer on our Sears PartsDirect website

Learn about all the convenient features on our Sears PartsDirect website that make your parts purchases easier.