One of the most common maintenance tasks is replacing the spark plug. Using the correct spark plug socket size is crucial to avoid damaging the spark plug or the engine.
This guide provides a comprehensive lawn mower spark plug socket size chart to help you easily identify the correct size for your mower.
Lawn Mower Spark Plug Socket Size Chart
Most lawn mower spark plugs use standard hex sizes measuring 5/8-inch (16 mm) and 13/16-inch (21 mm). Some smaller engines use 3/8-inch (10 mm) sockets, especially for compact or older models.
Briggs & Stratton
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| 450E, 500E | 799728, 796596 | 5/8-inch (16 mm) | Deep |
| 675EXi, 825EXi | 494406, 796596 | 13/16-inch (21 mm) | Deep |
| 550EX Series | 796596 | 13/16-inch (21 mm) | Deep |
| 850EX Series | 494406 | 13/16-inch (21 mm) | Deep |
| Quantum Series | 398811 | 5/8-inch (16 mm) | Deep |
| 950 Series | 799728 | 5/8-inch (16 mm) | Deep |
| Sprint Series | 797003 | 13/16-inch (21 mm) | Deep |
Honda
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| GX160, GX200 | BPR6ES | 5/8-inch (16 mm) | Standard |
| GCV160, GCV190 | BPR5ES | 5/8-inch (16 mm) | Standard |
| GXV160, GXV190 | BPR6ES | 5/8-inch (16 mm) | Standard |
| GXV340, GXV390 | BPR6ES | 5/8-inch (16 mm) | Standard |
| HRX217, HRX537 | BPR5ES | 5/8-inch (16 mm) | Standard |
| GCV530 | BPR5ES | 5/8-inch (16 mm) | Standard |
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Kohler
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| XT650, CV740 | CHAMP RJ19LM | 5/8-inch (16 mm) | Deep |
| K241, K301 | CHAMP RJ20LM | 13/16-inch (21 mm) | Deep |
| Courage Series K341 | CHAMP RJ19LM | 5/8-inch (16 mm) | Deep |
| KT17, KT19 | CHAMP RJ20LM | 13/16-inch (21 mm) | Deep |
| CV22, CV23 | CHAMP RJ19LM | 5/8-inch (16 mm) | Deep |
| XT675, XT725 | CHAMP RJ20LM | 13/16-inch (21 mm) | Deep |
Tecumseh
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| TVS90, 100 | 640070A | 13/16-inch (21 mm) | Deep |
| H50, H60 | 640070A | 13/16-inch (21 mm) | Deep |
| OH195, OH200 | 640070A | 13/16-inch (21 mm) | Deep |
| LEV90, LEV100 | 640070A | 13/16-inch (21 mm) | Deep |
| TVM120 | 640070A | 13/16-inch (21 mm) | Deep |
Toro
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| 20332, 20632 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| Recycler 22 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| Super Recycler 21 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| TimeCutter 42 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| Personal Pace 22 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| Toro 20960 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
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John Deere
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| AM122565, MIA12210 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| D100, D110 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| E100, E120 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| X300, X320 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| L100, L120 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| GX215, GX225 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
Husqvarna
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| YTH1842, LT154 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| LGT2654 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| RZ5424 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| TS348XD | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| MZ61 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| HU700, HU725 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
Snapper
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| 2201051, 2201052 | CHAMP RJ19LM | 5/8-inch (16 mm) | Deep |
| XD21, XD23 | CHAMP RJ19LM | 5/8-inch (16 mm) | Deep |
| SP21, SP22 | CHAMP RJ19LM | 5/8-inch (16 mm) | Deep |
| SGM2100 | CHAMP RJ20LM | 13/16-inch (21 mm) | Deep |
| SP50 | CHAMP RJ20LM | 13/16-inch (21 mm) | Deep |
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MTD & Cub Cadet
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| 754-04193, 754-04194 (MTD) | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| 951-12252 (Cub Cadet) | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| 751-12252 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| 13A500, 13A600 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| XT1 Enduro | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
Ariens
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| 921063, 921064 | CHAMP RJ19LM | 13/16-inch (21 mm) | Deep |
| 920020, 920021 | CHAMP RJ19LM | 13/16-inch (21 mm) | Deep |
| 915065, 915066 | CHAMP RJ20LM | 13/16-inch (21 mm) | Deep |
| IKON Series | CHAMP RJ19LM | 13/16-inch (21 mm) | Deep |
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Troy-Bilt
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| TB300, TB400 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| XP Series | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| TB500 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
| TB42 | NGK BPR5ES | 5/8-inch (16 mm) | Standard |
Poulan / Poulan Pro
| Engine Model | Spark Plug Part Number | Socket Size | Socket Type |
|---|---|---|---|
| PP4218, PP5020 | CHAMP RJ19LM | 5/8-inch (16 mm) | Standard |
| 961350, 961351 | CHAMP RJ19LM | 5/8-inch (16 mm) | Standard |
| PP4624 | CHAMP RJ20LM | 13/16-inch (21 mm) | Deep |
| Poulan Pro PR5020 | CHAMP RJ19LM | 5/8-inch (16 mm) | Standard |
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How to Choose the Right Spark Plug Socket
- Check your spark plug’s hex size: Look at the spark plug specification in your mower’s manual. Common sizes are 5/8-inch and 13/16-inch.
- Consider the depth: If the spark plug is recessed deep in the engine, use a deep socket. Shallow sockets work for easily accessible plugs.
- Use a rubber insert or magnet: Many spark plug sockets have a rubber insert or magnetic end to hold the spark plug securely during removal or installation. This prevents the ceramic insulator from breaking.
- Keep it clean: Ensure the socket and spark plug are free of debris to prevent cross-threading or damaging the cylinder head.
Tips for Spark Plug Maintenance
- Replace regularly: Most manufacturers recommend replacing spark plugs every 25–50 hours of operation or at least once a season.
- Check the gap: Use a spark plug gap tool to ensure the correct gap for your engine model. An incorrect gap can lead to hard starting or poor engine performance.
- Inspect for damage: Cracked ceramic or burnt electrodes indicate a replacement is needed.
- Torque properly: Avoid over-tightening. Use a torque wrench if possible to match the manufacturer’s recommended torque.
Common Mistakes to Avoid
- Using the wrong socket size can strip the hex or break the spark plug.
- Not using a deep socket for recessed plugs can make removal very difficult.
- Forgetting to check the gap may lead to poor engine performance.
- Over-tightening can damage the engine cylinder head threads.
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FAQs
What is a standard spark plug socket size?
The most common standard size for lawn mower spark plugs is 5/8-inch (16 mm), though 13/16-inch (21 mm) is also widely used for larger engines.
How do I know what socket size I need?
Check your mower’s engine manual or inspect the spark plug. Most spark plugs will have a hex size indicated on the packaging or plug itself.
Can I use a regular socket instead of a spark plug socket?
It is possible, but not recommended. Regular sockets may not have the rubber insert or deep reach needed, increasing the risk of dropping or breaking the plug.
How deep should a spark plug socket be?
Use a deep socket for recessed spark plugs to ensure you can fully remove or install them without damaging the plug.
Is it necessary to torque spark plugs?
Yes, using the correct torque prevents over-tightening, which can damage the threads, or under-tightening, which can cause poor engine performance.
