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MTD
Gas Walk-Behind Mower

Model # 12A-446M729 Official MTD lawn mower

Here are the diagrams and repair parts for Official MTD 12A-446M729 lawn mower, as well as links to manuals and error code tables, if available.

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  • In the search box below, enter all or part of the part number or the part’s name.

Not all parts are shown on the diagrams—those parts are labeled NI, for “not illustrated”.

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For DIY troubleshooting advice and repair guides, visit our repair help section.

Owner’s manual

Model diagram and schematic

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ALL PARTS
Showing 10 of 91 parts  |
Blade-21" Mu 742-0741
#62

Mower parts diagram

Blade-21" mu

Part #742-0741

Replaced by #942-0741A

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Manufacturer substitution
This part replaces 742-0741. Substitute parts can look different from the original.
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$29.10 | 
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Bell Support 736-0524A
#75

Mower parts diagram

Bell support

Part #736-0524A

Replaced by #736-0524B-1

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Manufacturer substitution
This part replaces 736-0524A. Substitute parts can look different from the original.
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$6.58 | 
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Knob Wing Nut 720-0284
#12

Mower parts diagram

Knob wing nut

Part #720-0284

Replaced by #720-04072A

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Manufacturer substitution
This part replaces 720-0284. Substitute parts can look different from the original.
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Wheel Asm-8 634-0190
#88C

Mower parts diagram

Wheel asm-8

Part #634-0190

Replaced by #634-0190A

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Manufacturer substitution
This part replaces 634-0190. Substitute parts can look different from the original.
$34.92 | 
15% OFF Phone Price : $40.92
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Lawn & Garden Equipment Carriage Bolt (replaces 1186069, 583108, 706-101080, 706-10602-12, 791-182213) 710-0703
#34

Mower parts diagram

Lawn & garden equipment carriage bolt (replaces 1186069, 583108, 706-101080, 706-10602-12, 791-182213)

Part #710-0703

This item is not returnable
$6.46 | 
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Yard Machines Lawn & Garden Equipment Wing Nut (replaces 01002925, 920-0279) 720-0279
#14

Mower parts diagram

Yard machines lawn & garden equipment wing nut (replaces 01002925, 920-0279)

Part #720-0279

This item is not returnable
$6.87 | 
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Yard Machines Lawn & Garden Equipment Guide Bolt 710-1205
#15

Mower parts diagram

Yard machines lawn & garden equipment guide bolt

Part #710-1205

This item is not returnable
$5.01 | 
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Complete Wheel 734-2042
#88H

Mower parts diagram

Complete wheel

Part #734-2042

Replaced by #734-2042A

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Manufacturer substitution
This part replaces 734-2042. Substitute parts can look different from the original.
$34.16 | 
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Yard Machines Lawn & Garden Equipment Screw 710-1017
#28

Mower parts diagram

Yard machines lawn & garden equipment screw

Part #710-1017

This item is not returnable
$12.71 | 
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Nut 712-0431
#68

Mower parts diagram

Nut

Part #712-0431

Replaced by #912-0431

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Manufacturer substitution
This part replaces 712-0431. Substitute parts can look different from the original.
This item is not returnable
$7.57 | 
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Symptoms for gas walk-behind mowers

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

View all

Why won't my lawn mower move?

Main causes: drive control cable failure, worn or broken drive belt, bad transmission, broken drive wheel…

Read more

Why does my lawn mower run rough?

Main causes: engine needs tune up, dirty or clogged carburetor, damaged flywheel key…

Read more

Why does my lawn mower stall?

Main causes: dirty carburetor, bad spark plug, clogged air filter, engine choke problems, clogged gas cap vent…

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Why does my lawn mower vibrate a lot?

Main causes: damaged cutting blade, loose cutting blade, damaged flywheel key, engine needs tune up…

Read more

Why won't my lawn mower start?

Main causes: stale gas, engine needs tune up, bad spark plug, dead battery, bad recoil starter, faulty safety switch, ba…

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Why does my lawn mower cut unevenly?

Main causes: uneven wheel height settings, damaged wheel, dull or damaged cutting blade…

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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.

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How to replace a lawn mower spark plug

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 cr…

Read more
Repair difficulty
Time required
 15 minutes or less
How to replace a lawn mower drive cable

How to replace a lawn mower drive cable

The drive cable engages the transmission to spin the drive wheels and move the mower across the grass. Replace the drive…

Read more
Repair difficulty
Time required
 60 minutes or less
How to replace a lawn mower starter rope

How to replace a lawn mower starter rope

These step-by-step instructions show how to replace a broken starter pull rope on a walk-behind lawn mower.…

Read more
Repair difficulty
Time required
 30 minutes or less

Effective articles & videos to help repair your walk-behind mowers

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

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Tapping into a new feature in the Search Bar on Sears PartsDirect

Tapping into a new feature in the Search Bar on Sears PartsDirect

Learn about a new feature added to the Search Bar on Sears PartsDirect…

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Introducing new technical repair content that we’re developing for the Sears Technical Institute

Introducing new technical repair content that we’re developing for the Sears Technical Institute

Learn about Sears Technical Institute and the advanced technical content being developed for aspiring appliance techs.…

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Top questions about Sears and Sears PartsDirect

Top questions about Sears and Sears PartsDirect

Get answers to frequently asked questions about Sears and Sears PartsDirect.…

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