Incorrect valve clearance can lead to issues such as reduced power, increased fuel consumption, misfiring, or even severe engine damage. This blog post provides a detailed overview of Briggs & Stratton valve clearance, its importance, and a comprehensive chart covering valve clearance specifications for various engine models, presented in an easy-to-read table format.
Briggs & Stratton Valve Clearance Chart
L-Head Aluminum/Cast Sleeve Single Cylinder Engines
| Model Series | Intake Valve Clearance (inches) | Exhaust Valve Clearance (inches) |
|---|---|---|
| 60000 | 0.005 – 0.007 | 0.007 – 0.009 |
| 80000 | 0.005 – 0.007 | 0.007 – 0.009 |
| 90000 | 0.005 – 0.007 | 0.007 – 0.009 |
| 10A000–10M000 | 0.005 – 0.007 | 0.007 – 0.009 |
| 110000 | 0.005 – 0.007 | 0.007 – 0.009 |
| 120000 | 0.005 – 0.007 | 0.007 – 0.009 |
| 130000 | 0.005 – 0.007 | 0.009 – 0.011 |
| 170000 | 0.005 – 0.007 | 0.009 – 0.011 |
| 171700 | 0.005 – 0.007 | 0.009 – 0.011 |
| 190000 | 0.005 – 0.007 | 0.009 – 0.011 |
| 191700 | 0.005 – 0.007 | 0.009 – 0.011 |
| 220000 | 0.005 – 0.007 | 0.009 – 0.011 |
| 250000 | 0.005 – 0.007 | 0.009 – 0.011 |
| 280000 | 0.005 – 0.007 | 0.009 – 0.011 |
L-Head Cast Iron Single Cylinder Engines
| Model Series | Intake Valve Clearance (inches) | Exhaust Valve Clearance (inches) |
|---|---|---|
| 230000 | 0.007 – 0.009 | 0.017 – 0.019 |
| 240000 | 0.007 – 0.009 | 0.017 – 0.019 |
| 320000 | 0.007 – 0.009 | 0.017 – 0.019 |
L-Head Opposed Twin Cylinder Engines
| Model Series | Intake Valve Clearance (inches) | Exhaust Valve Clearance (inches) |
|---|---|---|
| 400000 | 0.004 – 0.006 | 0.007 – 0.009 |
| 420000 | 0.004 – 0.006 | 0.007 – 0.009 |
| 460000 | 0.004 – 0.006 | 0.007 – 0.009 |
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Overhead Valve (OHV) Single Cylinder Engines
| Model Series | Intake Valve Clearance (inches) | Exhaust Valve Clearance (inches) |
|---|---|---|
| 50000 | 0.004 – 0.008 | 0.004 – 0.008 |
| 85400 | 0.002 – 0.004 | 0.002 – 0.004 |
| 97700, 99700 | 0.005 – 0.007 | 0.005 – 0.007 |
| 115400, 117400, 118400 | 0.002 – 0.004 | 0.002 – 0.004 |
| 120000 (Horizontal Shaft) | 0.004 – 0.006 | 0.009 – 0.011 |
| 120000 (Vertical Shaft) | 0.004 – 0.006 | 0.004 – 0.006 |
| 138400 | 0.002 – 0.004 | 0.002 – 0.004 |
| 185400 | 0.002 – 0.004 | 0.002 – 0.004 |
| 200000 | 0.004 – 0.006 | 0.004 – 0.006 |
| 210000 (Horizontal Shaft) | 0.004 – 0.006 | 0.004 – 0.006 |
| 210000 (Vertical Shaft) | 0.004 – 0.006 | 0.004 – 0.006 |
| 235400, 245400 | 0.004 – 0.006 | 0.004 – 0.006 |
| 280000 | 0.003 – 0.005 | 0.005 – 0.007 |
| 310000 | 0.003 – 0.005 | 0.005 – 0.007 |
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What is Valve Clearance and Why is it Important?
Valve clearance refers to the small gap between the valve stem and the rocker arm or tappet in an internal combustion engine.
This gap ensures that the valves can fully open and close at the right time during the engine’s cycle, allowing for proper air and fuel intake and exhaust expulsion.
Briggs & Stratton engines, whether single-cylinder, V-twin, overhead valve (OHV), or L-head (side valve), require periodic valve clearance checks and adjustments to maintain optimal performance.
Incorrect valve clearance can cause several problems:
- Too tight: Valves may not close fully, leading to compression loss, overheating, or burnt valves.
- Too loose: Excessive clearance can cause noisy operation, reduced power, and accelerated wear on valve components.
- Neglecting adjustments: Over time, valve clearances can change due to wear, leading to poor engine performance or failure.
Regular valve clearance maintenance, guided by the correct specifications for your engine model, ensures smooth operation, fuel efficiency, and a longer engine lifespan.
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How to Adjust Valve Clearance
1. Prepare the Engine: Ensure the engine is cold, as valve clearances are typically measured with a cold engine to account for thermal expansion. Remove the spark plug and secure the spark plug lead away from it to prevent accidental starting.
2. Access the Valves: Remove the valve cover using a socket wrench or nut driver. You may need to remove other components, such as the air cleaner assembly or muffler, depending on the engine model.
3. Set Piston Position: Rotate the crankshaft until the piston is at the top dead center (TDC) on the compression stroke. For some models, Briggs & Stratton recommends setting the piston 1/4 inch (6 mm) past TDC to avoid interference from the compression release mechanism.
4. Measure Clearance: Use a feeler gauge to measure the gap between the valve stem and the rocker arm. Compare the measurement to the specifications for your engine model.
5. Adjust Clearance: If the clearance is outside the recommended range, loosen the lock nut on the rocker’s arm and turn the adjustment screw to achieve the correct gap. Tighten the lock nut while holding the screw in place, then recheck the clearance.
6. Reassemble and Test: Reinstall the valve cover with a new gasket if needed, reassemble any removed components, and test the engine to ensure smooth operation.
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Common Issues and Troubleshooting
If valve clearance is not within the specified range, you may encounter:
- Hard Starting: Excessive clearance can reduce compression, making the engine difficult to start, especially when hot.
- Backfiring or Smoke: Incorrect clearance may cause blow-by or improper combustion, leading to backfiring through the carburetor or smoke from the crankcase.
- Overheating or Wear: Tight clearances can prevent valves from closing fully, causing overheating or accelerated wear on valve seats and guides
Final words
Proper valve clearance is essential for the efficient operation of Briggs & Stratton engines. By adhering to the specified clearances for your engine model, you can ensure longevity and optimal performance.
Regular maintenance and adjustments, as outlined above, will help prevent common engine issues and maintain the reliability that Briggs & Stratton engines are known for.
