Incorrect spark plug gaps can lead to misfiring, poor fuel efficiency, or even engine damage. Briggs & Stratton emphasizes using the correct spark plug and gap, warning that while some plugs may fit, only the recommended type ensures peak performance.
In this detailed post guide, we’ll cover everything you need to know, including a complete Briggs and Stratton spark plug gap chart, maintenance tips, tools, and troubleshooting advice.
Briggs and Stratton Spark Plug Gap Chart
625EX / 675EX / 725EXi Series
| Model Number | Displacement | Spark Plug | Gap Size (inches) |
|---|---|---|---|
| 126T02 | 150cc | RJ19LM | 0.030″ |
| 128M02 | 163cc | RJ19LM | 0.030″ |
| 09J902 | 163cc | RJ19LM | 0.030″ |
EXi Series
| Model Number | Displacement | Spark Plug | Gap Size (inches) |
|---|---|---|---|
| 123K02 | 163cc | RJ19LMC | 0.030″ |
| 104M02 | 163cc | RJ19LMC | 0.030″ |
Quantum Series
| Model Number | Displacement | Spark Plug | Gap Size (inches) |
|---|---|---|---|
| 12H802 | 163cc | RJ19LM | 0.030″ |
| 12T802 | 190cc | RJ19LM | 0.030″ |
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Classic Series
| Model Number | Displacement | Spark Plug | Gap Size (inches) |
|---|---|---|---|
| 12S902 | 148cc | RJ19LM | 0.030″ |
Intek Series (Single-Cylinder)
| Model Number | Displacement | Spark Plug | Gap Size (inches) |
|---|---|---|---|
| 31C707 | 500cc | RC12YC | 0.030″ |
| 31H777 | 540cc | RC12YC | 0.030″ |
| 31R907 | 500cc | RC12YC | 0.030″ |
Vanguard V-Twin Series
| Model Number | Displacement | Spark Plug | Gap Size (inches) |
|---|---|---|---|
| 356447 | 570cc | RC14YC | 0.030″–0.035″ |
| 386447 | 627cc | RC12YC | 0.030″–0.035″ |
| 543477 | 993cc | RC14YC | 0.030″–0.035″ |
Related John Deere Spark Plug Gap Chart(For All Models)
Snow Series Engines
| Model Number | Displacement | Spark Plug | Gap Size (inches) |
|---|---|---|---|
| 20H114 | 250cc | 796112S | 0.030″ |
| 21M314 | 305cc | 491055S | 0.030″ |
PowerBuilt OHV Series
| Model Number | Displacement | Spark Plug | Gap Size (inches) |
|---|---|---|---|
| 31R907 | 500cc | RC12YC | 0.030″ |
| 31S977 | 540cc | RC12YC | 0.030″ |
Related Briggs and Stratton Head Gasket Chart(For All Models)
Industrial Plus / DOV Series
| Model Number | Displacement | Spark Plug | Gap Size (inches) |
|---|---|---|---|
| 12F802 | 206cc | RC12YC | 0.030″ |
| 12F702 | 206cc | RC12YC | 0.030″ |
Recommended Tools for Measuring Spark Plug Gaps
- Spark plug gap gauge (coin or wire type)
- Feeler gauge
- Needle-nose pliers (for adjusting)
- Anti-seize compound (optional but recommended)
Related Briggs and Stratton Belt Size Chart(For All Models)
Tips for Gapping and Replacing Spark Plugs
- Use the Right Tools: A wire-style gap tool is ideal for precise adjustments. Avoid bending electrodes more than 0.008 inches to prevent misalignment.
- Check Condition: Inspect the spark plug for wear, fouling, or damage. Replace if the electrodes are worn or the plug is over two years old.
- Torque Correctly: Tighten to the recommended torque (e.g., 15 lb-ft for RJ19LM).
- Troubleshooting: If your engine misfires or won’t start, verify the gap and check the ignition coil or kill wire.
- Maintenance Schedule: Replace spark plugs annually or every 100 hours of operation for optimal performance.
Common Issues and Solutions
- Engine Won’t Start: A misgapped plug or faulty ignition coil may be the culprit. Test for spark and adjust the gap as needed.
- Backfiring: This can result from an incorrect plug or gap, or issues with the carburetor or governor settings.
- Poor Performance: Ensure the plug matches the engine’s specifications. For example, using a short-thread plug in an OHV engine can cause piston contact.
Related Briggs & Stratton Valve Clearance Chart(For All Models)
FAQs
What is the standard spark plug gap for Briggs and Stratton?
The standard gap is 0.030″ for most models, but always confirm using your model number.
What happens if the spark plug gap is wrong?
It can lead to misfires, poor performance, starting issues, and increased fuel consumption.
Can I use any spark plug for my mower engine?
No. Use the specified plug type and gap for your model to avoid engine damage.
How often should I check the spark plug gap?
Every 25–50 hours of use or at the start of every mowing season.
How do I know if my spark plug needs replacing?
Look for burnt electrodes, carbon build-up, cracks, or engine issues like hard starting or rough idling.
Are pre-gapped spark plugs accurate?
Sometimes, but they can shift during shipping. Always double-check before installation.
Final words
The spark plug gap may be small, but it plays a big role in your Briggs and Stratton engine’s health. Keeping the correct gap ensures smooth performance, easy starting, and longer engine life. Use the chart above, follow the tips, and you’ll never be left pulling the starter rope in frustration.
