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Craftsman
Riding Mowers & Tractors

Model # 3904 Official Craftsman lawn tractor

Here are the diagrams and repair parts for Official Craftsman 3904 lawn tractor, 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.

Model diagram and schematic

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ALL PARTS
Showing 10 of 758 parts  |
Piston Ring Assembly 12181-2109-0
#20A

Piston - crankshaft diagram

Piston ring assembly

Part #12181-2109-0

The manufacturer no longer makes this part, and there's no substitute part

Adjuster 66071-4287-0
#190

Brake pedal diagram

Adjuster

Part #66071-4287-0

The manufacturer no longer makes this part, and there's no substitute part

Washer 04011-5006-0
#130

Fender diagram

Washer

Part #04011-5006-0

The manufacturer no longer makes this part, and there's no substitute part

Carburetor 12181-4401-0
Carburetor

Part #12181-4401-0

The manufacturer no longer makes this part, and there's no substitute part

Guide, Lever 66082-5217-0
#100

Fender diagram

Guide, lever

Part #66082-5217-0

The manufacturer no longer makes this part, and there's no substitute part

Bolt 01754-5083-5
#30

Transmission case diagram

Bolt

Part #01754-5083-5

The manufacturer no longer makes this part, and there's no substitute part

Bolt 03024-5051-2
#220

Transmission case (hst) diagram

Bolt

Part #03024-5051-2

The manufacturer no longer makes this part, and there's no substitute part

Bolt 01350-1051-0
#170

Transmission case (hst) diagram

Bolt

Part #01350-1051-0

The manufacturer no longer makes this part, and there's no substitute part

V-belt 66082-4353-0
#200

Tension arm diagram

V-belt

Part #66082-4353-0

The manufacturer no longer makes this part, and there's no substitute part

Lift Rod 66071-5184-0
#140

Lift link diagram

Lift rod

Part #66071-5184-0

The manufacturer no longer makes this part, and there's no substitute part

Most common symptoms to help you fix your riding mowers & tractors

Choose a symptom to see related riding mower and lawn tractor repairs.

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Why is my riding mower not cutting evenly?

Main causes: unlevel mower deck, dull or damaged cutting blades, worn mandrel pulleys, bent mower deck, engine needs tun…

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Why won't my riding mower start?

Main causes: dead battery, stale fuel, bad starter solenoid, ignition system problem, bad ignition interlock switch, clo…

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Why is the steering loose on my riding mower?

Main causes: damaged tie rods, bent or worn wheel spindle, worn front axle, damaged sector gear assembly…

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How do I fix a flat tire on my riding mower?

Main causes: punctured tire or inner tube, leaky valve stem, damaged wheel rim…

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Why won't my riding mower cut grass?

Main causes: worn or broken blade belt, broken belt idler pulley, blade clutch cable failure, bad PTO switch, damaged ma…

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How do I charge a dead battery on my riding mower?

Main causes: faulty battery, bad alternator…

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Why does my riding mower deck vibrate?

Main causes: damaged cutting blade, worn deck pulley, damaged mandrel pulley, loose fasteners on mower deck components…

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Why does my riding mower creep in neutral?

Main causes: shift lever needs adjustment, neutral control needs adjustment…

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Why won't my riding mower move?

Main causes: worn or broken ground drive belt, bad seat switch, transaxle freewheel control engaged, transaxle failure, …

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Most common repair guides to help fix your riding mowers & tractors

These step-by-step repair guides will help you safely fix what’s broken on your riding mower or lawn tractor.

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How to replace the seat switch on a riding lawn mower

How to replace the seat switch on a riding lawn mower

Follow the steps in this guide to install a new riding mower seat switch in about 15 minutes.…

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Repair difficulty
Time required
 15 minutes or less
How to replace a riding lawn mower spark plug

How to replace a riding lawn mower spark plug

If the engine is hard to start or if the spark plug electrode is burnt or cracked, take 15 minutes to replace it.…

Read more
Repair difficulty
Time required
 15 minutes or less
How to replace a riding lawn mower rear tire

How to replace a riding lawn mower rear tire

Your mower can’t run on a damaged rear tire. Here’s how to install a new one.…

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Repair difficulty
Time required
 60 minutes or less

Effective articles & videos to help repair your riding mowers & tractors

Use the advice and tips in these articles and videos to get the most out of your riding mower or lawn tractor.

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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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Riding lawn mower engine clicks but doesn't turn over video

Riding lawn mower engine clicks but doesn't turn over video

Check the starter solenoid, starter motor, wiring, battery and engine.…

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