When your lawn mower isn’t starting properly, misfiring, or running rough, the spark plug is often to blame. One overlooked detail in spark plug maintenance is the spark plug gap, a small but critical space that determines how effectively your engine ignites the fuel.
Using the correct spark plug gap is essential for proper engine combustion, fuel efficiency, and engine longevity.
In this post, we’ll cover everything you need to know about spark plug gaps for lawn mowers, and we’ll include a handy Spark Plug Gap Chart with settings for all popular mower brands and models.
Lawn Mower Spark Plug Gap Chart
Briggs & Stratton
| Model | Engine Type | Spark Plug Type | Gap (inches) |
|---|---|---|---|
| Quantum 625 | L-Head | Champion RJ19LM, Briggs 796112S | 0.030 |
| Intek 206 | OHV | Champion RC12YC, Briggs 491055S | 0.030 |
| 550EX Series | L-Head | Briggs 802592S, NGK BPR6ES | 0.030 |
| 725EXI Series | OHV | Champion QC12YC, Briggs 496018S | 0.030 |
| 875 Professional | OHV | Briggs 796112S, NGK BCPR5ES | 0.030 |
| 190cc Sprint | L-Head | Champion RJ19LM, Autolite 255 | 0.030 |
| Vanguard 18 HP | V-Twin | Champion RC12YC, NGK BPR5ES | 0.030 |
| 675 Series | L-Head | Briggs 5095K, Champion J19LM | 0.030 |
| 500E Series | L-Head | Champion RJ19LM, Briggs 802592S | 0.030 |
| 800 Series | OHV | Champion QC12YC, Briggs 496018S | 0.030 |
Honda
| Model | Engine Type | Spark Plug Type | Gap (inches) |
|---|---|---|---|
| GCV160 | OHV | NGK BPR5ES, Champion RN12YC | 0.030 |
| GCV190 | OHV | NGK BPR6ES, Champion RN9YC | 0.030 |
| HRX217 | GCV200 | NGK BPR5ES, Denso W16EPR-U | 0.030 |
| HRR216 | GCV160 | NGK BPR5ES, Champion RN12YC | 0.028 |
| HRC216 | GCV160 | NGK BPR6ES, Denso W20EPR-U | 0.030 |
| GX160 | OHV | NGK BPR6ES, Champion RN9YC | 0.030 |
| GX200 | OHV | NGK BPR5ES, Denso W16EPR-U | 0.030 |
| GC190 | OHV | NGK BPR6ES, Champion RN9YC | 0.028 |
| GXV160 | OHV | NGK BPR5ES, Champion RN12YC | 0.030 |
| HRN216 | GCV170 | NGK BPR5ES, Champion RN12YC | 0.030 |
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Toro
| Model | Engine Type | Spark Plug Type | Gap (inches) |
|---|---|---|---|
| Recycler 22 | Briggs 675EXi | Champion RJ19LM, Briggs 796112S | 0.030 |
| Super Recycler | Honda GCV170 | NGK BPR5ES, Champion RN12YC | 0.030 |
| TimeMaster 30 | Briggs 875 | Champion RC12YC, Briggs 491055S | 0.030 |
| 20332 | Kohler Courage | Champion RC12YC, NGK BCPR5ES | 0.030 |
| 20340 | Briggs 725EXi | Briggs 796112S, Champion QC12YC | 0.030 |
| 20041 | Tecumseh | Champion RJ19LM, Autolite 255 | 0.030 |
| 21332 | Briggs 625EX | Champion RJ19LM, NGK BPR6ES | 0.030 |
| 20371 | Honda GCV160 | NGK BPR5ES, Champion RN12YC | 0.028 |
| 20381 | Kohler 7000 | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
| 20350 | Briggs 650EXi | Champion RJ19LM, Briggs 796112S | 0.030 |
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Craftsman
| Model | Engine Type | Spark Plug Type | Gap (inches) |
|---|---|---|---|
| M110 | Briggs 550EX | Champion RJ19LM, Briggs 802592S | 0.030 |
| M250 | Briggs 725EXi | Champion QC12YC, Briggs 496018S | 0.030 |
| M270 | Honda GCV170 | NGK BPR5ES, Champion RN12YC | 0.030 |
| M140 | Briggs 625EX | Champion RJ19LM, NGK BPR6ES | 0.030 |
| M230 | Briggs 675EXi | Champion RJ19LM, Briggs 796112S | 0.030 |
| CMXGMAM1125500 | Kohler Courage | Champion RC12YC, NGK BCPR5ES | 0.030 |
| M310 | Briggs 875 | Champion RC12YC, Briggs 491055S | 0.030 |
| M105 | Briggs 500EX | Champion RJ19LM, Autolite 255 | 0.030 |
| M215 | Briggs 675EXi | Champion RJ19LM, Briggs 796112S | 0.030 |
| M320 | Honda GCV190 | NGK BPR6ES, Champion RN9YC | 0.030 |
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Husqvarna
| Model | Engine Type | Spark Plug Type | Gap (inches) |
|---|---|---|---|
| HU800AWD | Honda GCV190 | NGK BPR6ES, Champion RN9YC | 0.030 |
| LC221A | Briggs 625EX | Champion RJ19LM, Briggs 796112S | 0.030 |
| HU700F | Honda GCV160 | NGK BPR5ES, Champion RN12YC | 0.028 |
| HU725AWD | Briggs 725EXi | Champion QC12YC, Briggs 496018S | 0.030 |
| LC121P | Briggs 550EX | Champion RJ19LM, Briggs 802592S | 0.030 |
| HU675AWD | Kohler Courage | Champion RC12YC, NGK BCPR5ES | 0.030 |
| W526 | Briggs 675EXi | Champion RJ19LM, NGK BPR6ES | 0.030 |
| HU550FH | Briggs 550EX | Champion RJ19LM, Autolite 255 | 0.030 |
| YTH22V46 | Briggs V-Twin | Champion RC12YC, Briggs 491055S | 0.030 |
| TS138 | Briggs 650EXi | Champion RJ19LM, Briggs 796112S | 0.030 |
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John Deere
| Model | Engine Type | Spark Plug Type | Gap (inches) |
|---|---|---|---|
| JS36 | Briggs 625EX | Champion RJ19LM, Briggs 796112S | 0.030 |
| Z335E | Briggs V-Twin | Champion RC12YC, Briggs 491055S | 0.030 |
| LA105 | Briggs 675EXi | Champion RJ19LM, NGK BPR6ES | 0.030 |
| D110 | Briggs 725EXi | Champion QC12YC, Briggs 496018S | 0.030 |
| X300 | Kawasaki | NGK BPR4ES, Champion RN12YC | 0.030 |
| JS26 | Briggs 550EX | Champion RJ19LM, Briggs 802592S | 0.030 |
| E120 | Briggs 675EXi | Champion RJ19LM, Autolite 255 | 0.030 |
| Z425 | Briggs V-Twin | Champion RC12YC, NGK BCPR5ES | 0.030 |
| D140 | Briggs 725EXi | Champion QC12YC, Briggs 496018S | 0.030 |
| X350 | Kawasaki | NGK BPR4ES, Champion RN12YC | 0.030 |
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Kohler
| Model | Engine Type | Spark Plug Type | Gap (inches) |
|---|---|---|---|
| Courage XT-7 | OHV | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
| Command CV15 | OHV | Champion RC12YC, NGK BCPR5ES | 0.030 |
| KT725 | V-Twin | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
| Courage SV600 | OHV | Champion RC12YC, NGK BCPR5ES | 0.030 |
| 7000 Series | V-Twin | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
| XT675 | OHV | Champion RC12YC, NGK BCPR5ES | 0.030 |
| SV540 | OHV | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
| KT745 | V-Twin | Champion RC12YC, NGK BCPR5ES | 0.030 |
| Courage SV590 | OHV | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
| KT715 | V-Twin | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
Cub Cadet
| Model | Engine Type | Spark Plug Type | Gap (inches) |
|---|---|---|---|
| CC30H | Briggs 675EXi | Champion RJ19LM, Briggs 796112S | 0.030 |
| XT1 LT42 | Kohler Courage | Champion RC12YC, NGK BCPR5ES | 0.030 |
| SC100 | Briggs 550EX | Champion RJ19LM, Briggs 802592S | 0.030 |
| ZT1 50 | Kohler 7000 | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
| CC800 | Briggs 725EXi | Champion QC12YC, Briggs 496018S | 0.030 |
| XT2 LX46 | Briggs V-Twin | Champion RC12YC, Briggs 491055S | 0.030 |
| SC300 | Briggs 625EX | Champion RJ19LM, NGK BPR6ES | 0.030 |
| LTX1040 | Kohler Courage | Champion RC12YC, NGK BCPR5ES | 0.030 |
| ZT1 42 | Kohler 7000 | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
| XT1 GT50 | Kohler Command | Champion RC12YC, NGK BCPR5ES | 0.030 |
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Ariens
| Model | Engine Type | Spark Plug Type | Gap (inches) |
|---|---|---|---|
| IKON XD 52 | Kohler 7000 | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
| Edge 34 | Briggs 550EX | Champion RJ19LM, Briggs 802592S | 0.030 |
| Apex 60 | Kohler 7000 | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
| Zoom 42 | Briggs 725EXi | Champion QC12YC, Briggs 496018S | 0.030 |
| Edge 52 | Briggs 675EXi | Champion RJ19LM, Briggs 796112S | 0.030 |
| IKON XL 60 | Kawasaki | NGK BPR4ES, Champion RN12YC | 0.030 |
| Compact 24 | Briggs 650EXi | Champion RJ19LM, NGK BPR6ES | 0.030 |
| Zoom 50 | Kohler Courage | Champion RC12YC, NGK BCPR5ES | 0.030 |
Troy-Bilt
| Model | Engine Type | Spark Plug Type | Gap (inches) |
|---|---|---|---|
| TB110 | Briggs 550EX | Champion RJ19LM, Briggs 802592S | 0.030 |
| TB230 | Briggs 675EXi | Champion RJ19LM, Briggs 796112S | 0.030 |
| TBWC33 | Briggs 725EXi | Champion QC12YC, Briggs 496018S | 0.030 |
| Pony 42 | Briggs V-Twin | Champion RC12YC, Briggs 491055S | 0.030 |
| Bronco 46 | Kohler Courage | Champion RC12YC, NGK BCPR5ES | 0.030 |
| TB30 | Briggs 625EX | Champion RJ19LM, NGK BPR6ES | 0.030 |
| Mustang 50 | Kohler 7000 | Champion RC12YC, Kohler 25 132 12-S | 0.030 |
| TBWC28 | Honda GCV160 | NGK BPR5ES, Champion RN12YC | 0.028 |
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How to Measure and Adjust Spark Plug Gap
You’ll need a feeler gauge or spark plug gap tool to measure the gap. Here’s how:
- Remove the spark plug.
- Insert the appropriate feeler gauge between the electrodes.
- If the gauge fits snugly with slight resistance, the gap is correct.
- To adjust, gently bend the ground electrode using the tool until it matches the recommended gap.
Tips for Spark Plug Maintenance
- Check the gap every season or after 25 hours of use.
- Replace spark plugs every 100 hours of use or annually.
- Use OEM-recommended spark plugs for optimal performance.
- Avoid using worn or dirty plugs — they reduce fuel efficiency.
- Apply a small amount of anti-seize compound to the threads before reinstalling.
- Use a torque wrench when installing to avoid overtightening.
Symptoms of Incorrect Spark Plug Gap
If your lawn mower isn’t performing well, an incorrect spark plug gap might be the cause. Watch out for these symptoms:
- Hard to start
- Engine misfires
- Poor acceleration or rough idle
- Excessive fuel consumption
- Weak or no spark
Cross-Reference: Spark Plug Compatibility by Brand
| Plug Brand | Equivalent Types |
|---|---|
| Champion | RJ19LM, RC12YC |
| NGK | BPR5ES, BPR6ES, BPMR7A, BPR4ES |
| Bosch | WR9E, WR7DC+ |
| Autolite | 458, 446, 64 |
FAQs
What is the correct spark plug gap for a lawn mower?
The typical spark plug gap for a lawn mower is 0.030 inches (0.76 mm). However, always check your lawn mower’s user manual, as some engines (especially Honda, John Deere, or specific Briggs & Stratton models) may recommend a gap between 0.028 and 0.031 inches.
What happens if spark plugs are gapped too small?
If the spark plug gap is too small, it can cause:
- Weak or inconsistent spark
- Hard starts or no start
- Poor fuel combustion
- Reduced engine power and performance
- Higher emissions
A smaller gap may also lead to incomplete combustion, resulting in carbon buildup and fouled plugs over time.
How to know if a spark plug is bad?
Here are signs your spark plug may be bad:
- Engine misfires or runs rough
- Hard to start or won’t start at all
- Poor fuel economy
- Black, oily, or sooty plug tip
- Visible damage (cracked ceramic, worn electrodes)
- No spark when tested with a spark tester
Routine inspection and replacement (every 100 hours or annually) can prevent issues.
What is the spark plug gap for a petrol strimmer?
Most petrol strimmers (string trimmers) require a spark plug gap of around 0.020 to 0.030 inches.
For example:
- Stihl: 0.020 in
- Husqvarna: 0.025 in
- Echo: 0.024–0.026 in
What should the gap be on an NGK spark plug?
The default factory gap on NGK spark plugs is often set to 0.028 to 0.032 inches, depending on the type and intended use.
For small engine/lawn mower applications, NGK plugs like BPR5ES or BPR6ES typically use a gap of 0.030 inches.
Does spark plug gap affect performance?
Yes, spark plug gap directly affects performance by:
- Influencing spark strength and ignition timing
- Affecting fuel combustion quality
- Impacting engine starting, idling, and power delivery
- Causing engine misfires or detonation if improperly gapped
Both too wide and too narrow gaps can reduce performance and damage the engine.
What is the rule of thumb for spark plug gap?
The general rule of thumb for small engines (like lawn mowers, trimmers, chainsaws) is:
0.030 inches (0.76 mm)
This applies to most 4-stroke and 2-stroke engines unless specified otherwise.
