MTD
Gas Walk-Behind Mower

Model #12AE999P099 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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For DIY troubleshooting advice and repair guides, visit our repair help section.

    Showing 10 of 257 parts

    Lawn Mower 21-in Deck Mulching Blade

    #34

    Handle/deck/chute Diagram

    $23.99

    In Stock

    Lawn & Garden Equipment Lock Nut, 5/16-18

    #52

    Drive Diagram

    Lawn & garden equipment lock nut, 5/16-18

    Part #712-04063
    This item is not returnable
    $3.59 | 
    10% OFF 
    MSRP: $4.00

    In Stock

    Lawn Mower Blade Support

    #32

    Handle/deck/chute Diagram

    Lawn mower blade support

    Part #736-0524B
    This item is not returnable
    $5.99

    In Stock

    Lawn & Garden Equipment Nut

    #66

    Handle/deck/chute Diagram

    Lawn & garden equipment nut

    Part #712-04064
    This item is not returnable
    $2.89 | 
    10% OFF 
    MSRP: $3.20

    In Stock

    Lawn Mower Handle Knob

    #13

    Handle/deck/chute Diagram

    Lawn mower handle knob

    Part #720-04072A
    This item is not returnable
    $4.99 | 
    33% OFF 
    MSRP: $7.50

    In Stock

    Lawn Tractor Screw, 1/4-20 x 5/8-in

    #2

    Drive Diagram

    Lawn tractor screw, 1/4-20 x 5/8-in

    Part #710-1652
    This item is not returnable
    $2.99 | 
    7% OFF 
    MSRP: $3.20

    In Stock

    Lawn & Garden Equipment Carriage Bolt

    #23

    Handle/deck/chute Diagram

    Lawn & garden equipment carriage bolt

    Part #710-0703
    This item is not returnable
    $2.89 | 
    12% OFF 
    MSRP: $3.30

    In Stock

    Lawn & Garden Equipment Wing Nut

    #22

    Handle/deck/chute Diagram

    Lawn & garden equipment wing nut

    Part #712-0397A
    This item is not returnable
    $2.89 | 
    10% OFF 
    MSRP: $3.20

    In Stock

    Lawn Mower Zone Control Cable

    #11

    Handle/deck/chute Diagram

    $17.99 | 
    5% OFF 
    MSRP: $19.00

    In Stock

    Lawn Mower Wheel, Rear

    #6

    Drive Diagram

    Lawn mower wheel, rear

    Part #734-2010B
    $36.46 | 
    7% OFF 
    MSRP: $39.00

    In Stock

    Symptoms for gas walk-behind mowers

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

    Main causes: drive control cable failure, worn or broken drive belt, bad transmission, broken drive wheel
    Main causes: uneven wheel height settings, damaged wheel, dull or damaged cutting blade
    Main causes: dirty carburetor, bad spark plug, clogged air filter, engine choke problems, clogged gas cap vent
    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: 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 flywheel key on an OHV engine

    The flywheel key couples the flywheel to the engine crankshaft. Replace the flywheel key if it's broken.

    Repair difficulty
    Time required
     60 minutes or less
    April 1, 2013
    By Lyle Weischwill
    How to replace a lawn mower wheel

    Learn how replace a damaged wheel on a walk-behind lawn mower—it's a quick, easy fix.

    Repair difficulty
    Time required
     15 minutes or less
    April 1, 2013
    By Lyle Weischwill
    How to replace a lawn mower safety switch

    The safety switch stops the engine when you release the lever on the handle. This repair guide explains how to replace it if it's not working correctly.

    Repair difficulty
    Time required
     30 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.

    October 1, 2019

    Types of walk-behind mower blades video

    By Sears PartsDirect staff

    Learn about the different kinds of mower blades and how to maintain them.