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Cub Cadet
Gas Walk-Behind Mower

Model # SC621 Official Cub Cadet gas lawn mower

Here are the diagrams and repair parts for Official Cub Cadet SC621 gas 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 158 parts  |
Blade-21" Mu 742-0741
#67

Deck/chute 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
#69

Deck/chute 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 Assembly 720-0241
#3

Handle/bag/cover diagram

Knob assembly

Part #720-0241

Replaced by #720-04072A

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Manufacturer substitution
This part replaces 720-0241. Substitute parts can look different from the original.
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Ball Bearing 741-0600
#7

Transmission assembly diagram

Ball bearing

Part #741-0600

Replaced by #941-0600

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Manufacturer substitution
This part replaces 741-0600. Substitute parts can look different from the original.
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Kill Switch 746-0912
#14

Handle/bag/cover diagram

Kill switch

Part #746-0912

Replaced by #946-1130

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Manufacturer substitution
This part replaces 746-0912. Substitute parts can look different from the original.
This item is not returnable
$14.49 | 
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Aircap Lawn Tractor Screw (replaces 150011, 910-0134) 710-0134
#1

Deck/chute diagram

Aircap lawn tractor screw (replaces 150011, 910-0134)

Part #710-0134

This item is not returnable
$6.55 | 
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Lawn & Garden Equipment Carriage Bolt (replaces 1186069, 583108, 706-101080, 706-10602-12, 791-182213) 710-0703
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
#6

Handle/bag/cover 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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Lawn & Garden Equipment Push Cap (replaces 1917798, 926-0214) 726-0214
#75

Deck/chute diagram

Lawn & garden equipment push cap (replaces 1917798, 926-0214)

Part #726-0214

This item is not returnable
$15.99 | 
11% OFF Phone Price : $17.99
In Stock
Sears Lawn & Garden Equipment Plastic Plug 721-0325
#25

Transmission assembly diagram

Sears lawn & garden equipment plastic plug

Part #721-0325

This item is not returnable
$6.75 | 
13% OFF Phone Price : $7.75
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Symptoms for gas walk-behind mowers

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

View all

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 does my lawn mower cut unevenly?

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

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 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 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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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 rebuild a lawn mower carburetor

How to rebuild a lawn mower carburetor

The carburetor mixes air with fuel to drive the piston. Rebuild the carburetor if it's clogged or leaks.…

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Repair difficulty
Time required
 60 minutes or less
How to replace a lawn mower recoil starter on an OHV engine

How to replace a lawn mower recoil starter on an OHV engine

Replace the recoil starter if it doesn't move when you pull the starter rope.…

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

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.…

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Repair difficulty
Time required
 15 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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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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Types of walk-behind mower blades video

Types of walk-behind mower blades video

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

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