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MTD
Gas Walk-Behind Mower

Model # 12A-B2AQ799 Official MTD lawn mower

Here are the diagrams and repair parts for Official MTD 12A-B2AQ799 lawn mower, as well as links to manuals and error code tables, if available.

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

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Owner’s manual

Model diagram and schematic

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Troybilt Lawn Mower 21-in Deck Mulching Blade (replaces 01002810, 742-0741a, 942-04276, 942-0741) 942-0741A
#24

Lawn mower diagram

Troybilt lawn mower 21-in deck mulching blade (replaces 01002810, 742-0741a, 942-04276, 942-0741)

Part #942-0741A

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Lawn Mower Grass Bag 964-04154
#38

Lawn mower diagram

Lawn mower grass bag

Part #964-04154

Replaced by #964-04154B

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Manufacturer substitution
This part replaces 964-04154. Substitute parts can look different from the original.
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Lawn Mower Wheel, 8 X 2-in 634-05040
#17

Lawn mower diagram

Lawn mower wheel, 8 x 2-in

Part #634-05040

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Lawn Mower Rear Skirt 731-07203
#36

Lawn mower diagram

Lawn mower rear skirt

Part #731-07203

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Lawn Mower Grass Bag Frame (replaces 647-04271, 747-05226) 647-04271-0637
#39

Lawn mower diagram

Lawn mower grass bag frame (replaces 647-04271, 747-05226)

Part #647-04271-0637

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Yard Machines Lawn & Garden Equipment Nut 712-04064
#32

Lawn mower diagram

Yard machines lawn & garden equipment nut

Part #712-04064

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Lawn Mower Lower Handle Knob (replaces 720-05066) 720-05066A
#30

Lawn mower diagram

Lawn mower lower handle knob (replaces 720-05066)

Part #720-05066A

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Lawn Mower Zone Control Cable (replaces 946-1113) 946-1113A
#34

Lawn mower diagram

Lawn mower zone control cable (replaces 946-1113)

Part #946-1113A

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Yard Machines Lawn Mower Handle Knob (replaces 01000382, 113589, 720-04072, 720-04125) 720-04072A
#9

Lawn mower diagram

Yard machines lawn mower handle knob (replaces 01000382, 113589, 720-04072, 720-04125)

Part #720-04072A

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Lawn Tractor Screw 710-04998
#7

Lawn mower diagram

Lawn tractor screw

Part #710-04998

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Symptoms for gas walk-behind mowers

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

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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 cut unevenly?

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

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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…

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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 stall?

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

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Why won't my lawn mower move?

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

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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…

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

How to replace a lawn mower blade

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

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

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 re…

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Repair difficulty
Time required
 45 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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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.…

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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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