MTD
Gas Walk-Behind Mower

Model #12BVB1BB799 Official MTD lawn mower

Here are the diagrams and repair parts for MTD 12BVB1BB799 lawn mower, as well as links to manuals and error code tables, if available.

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  • Click a diagram to see the parts shown on that diagram.
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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

Showing 10 of 59 parts

Lawn Mower Wheel, 8 x 2-in#17

Lawn mower Diagram

Lawn mower wheel, 8 x 2-in

Part #634-05040
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Lawn Mower Blade Support#31

Lawn mower Diagram

Lawn mower blade support

Part #736-0524B
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Lawn Mower Zone Control Cable#34

Lawn mower Diagram

Lawn mower zone control cable

Part #946-04661A
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Lawn & Garden Equipment Hex Bolt, 3/8-24 x 1-1/2-in#25

Lawn mower Diagram

Lawn & garden equipment hex bolt, 3/8-24 x 1-1/2-in

Part #710-1044
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Lawn Mower 21-in Deck Mulching Blade#24

Lawn mower Diagram

Lawn mower 21-in deck xtreme mulching blade

Part #942-0741-X
Replaced by #742P0741-X
?
Manufacturer substitution
This part replaces 942-0741-X. Substitute parts can look different from the original.
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Lawn Mower Blade Adapter#23

Lawn mower Diagram

Lawn mower blade adapter

Part #687-02528
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Lawn Mower Screw#42

Lawn mower Diagram

Lawn mower screw

Part #710-04995A
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Lawn Mower Deck Water Nozzle#55

Lawn mower Diagram

Lawn mower deck water nozzle

Part #921-04041
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Lawn Mower Drive Pinion Gear, Left

Lawn mower drive pinion gear, left

Part #917-04802
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Lawn & Garden Equipment Wing Nut#5

Lawn mower Diagram

Lawn & garden equipment wing nut

Part #720-0279
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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: dirty carburetor, bad spark plug, clogged air filter, engine choke problems, clogged gas cap vent
Main causes: engine needs tune up, dirty or clogged carburetor, damaged flywheel key
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.

March 1, 2016
By Lyle Weischwill
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
March 1, 2016
By Lyle Weischwill
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

By Lyle Weischwill

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

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

By Lyle Weischwill

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

August 5, 2022

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

By Lyle Weischwill

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