Briggs and Stratton 675 Engine Series (5 Fixes for Firewood Gear)

Like a well-seasoned axe, a finely tuned engine is essential for splitting wood and keeping warm through the winter. The Briggs & Stratton 675 Series engine has been a workhorse for many, powering everything from lawnmowers to log splitters. But like any machine, it can develop quirks, especially when put to the rigorous demands of firewood processing. Over the years, I’ve wrestled with my fair share of engine troubles, often in the dead of winter with a looming woodpile. I’ve compiled five essential fixes to keep your Briggs & Stratton 675 Series engine roaring, ensuring your firewood gear operates smoothly and efficiently.

Troubleshooting the Briggs & Stratton 675 Engine Series: 5 Fixes for Firewood Gear

Before diving into the fixes, let’s set the stage. The Briggs & Stratton 675 Series is a single-cylinder, four-stroke engine commonly found on various outdoor power equipment, including log splitters, chippers, and some smaller firewood processors. Its popularity stems from its reliability, ease of maintenance, and relatively affordable price point. However, its simplicity doesn’t make it immune to problems. The issues I’ll address are those I’ve repeatedly encountered while processing firewood, from small-scale hobby operations to larger, more demanding tasks.

1. The Case of the Stubborn Start: Fuel System Diagnostics

One of the most common frustrations I’ve faced is a 675 Series engine that refuses to start. More often than not, the culprit is the fuel system. Fuel-related issues can manifest in a few ways: the engine cranks but doesn’t fire, it starts briefly and then dies, or it runs rough and sputters. Here’s a breakdown of how I approach diagnosing and fixing these problems:

1.1 Fuel Quality and Freshness

The first thing I always check is the fuel itself. Gasoline, especially when mixed with ethanol, degrades over time. Ethanol attracts water, leading to phase separation, where the ethanol and water separate from the gasoline, creating a corrosive mixture that can damage engine components.

• The Fix: I always recommend using fresh fuel, ideally less than 30 days old. For seasonal equipment like log splitters, I drain the fuel tank and carburetor before storing it for the off-season. Add a fuel stabilizer like STA-BIL to the fuel if you plan to store it for longer periods. I’ve personally found that using premium, ethanol-free gasoline significantly reduces fuel-related issues, especially in older engines.

• Data Point: According to the EPA, gasoline can begin to degrade in as little as 30 days, with significant degradation occurring after 90 days, especially in warmer climates. Ethanol-blended fuels are even more susceptible to degradation.

1.2 Carburetor Cleaning

The carburetor is responsible for mixing air and fuel in the correct ratio for combustion. Over time, varnish and deposits from old fuel can clog the carburetor’s jets and passages, leading to poor performance or a no-start condition.

• The Fix: I typically start by trying to clean the carburetor without disassembling it. I use a carburetor cleaner spray, available at most auto parts stores, and spray it directly into the carburetor intake while the engine is running (if it starts). If that doesn’t work, I disassemble the carburetor for a thorough cleaning.

  • Disassembly: Carefully remove the carburetor from the engine. Take pictures as you disassemble it to help with reassembly.
  • Cleaning: Use carburetor cleaner and small brushes or pipe cleaners to clean all the jets and passages. Pay particular attention to the main jet and pilot jet, which are often the first to clog.
  • Reassembly: Reassemble the carburetor, replacing any worn gaskets or O-rings.

• Personal Anecdote: I once spent an entire afternoon wrestling with a log splitter that wouldn’t start. After tearing down the carburetor and finding a tiny piece of debris blocking the main jet, the engine roared back to life. It’s amazing how such a small obstruction can cause so much trouble.

1.3 Fuel Filter Inspection and Replacement

The fuel filter prevents debris from entering the carburetor. A clogged fuel filter can restrict fuel flow, leading to engine stalling or poor performance.

• The Fix: I inspect the fuel filter regularly and replace it at least once a year, or more often if I’m using the equipment frequently. Fuel filters are inexpensive and easy to replace.

• Data Point: A clogged fuel filter can reduce fuel flow by as much as 50%, significantly impacting engine performance.

1.4 Fuel Line Inspection

Cracked or damaged fuel lines can leak air, disrupting fuel flow and causing the engine to run poorly or not start.

• The Fix: I visually inspect the fuel lines for cracks, leaks, or damage. If I find any issues, I replace the fuel lines with new ones of the correct size and type.

• Technical Requirement: Use fuel lines specifically designed for gasoline engines. Avoid using generic rubber tubing, as it can degrade quickly and cause problems. The internal diameter of fuel lines should match the original specifications.

2. The Mystery of the Misfiring Engine: Ignition System Checks

If the fuel system is in good order, the next area I investigate is the ignition system. The ignition system is responsible for creating the spark that ignites the air-fuel mixture in the cylinder. Common ignition-related problems include a weak spark, no spark, or intermittent misfires.

2.1 Spark Plug Inspection and Replacement

The spark plug is the heart of the ignition system. Over time, the spark plug can become fouled with carbon deposits, worn, or damaged, leading to a weak or non-existent spark.

• The Fix: I remove the spark plug and inspect it. If the spark plug is heavily fouled, cracked, or has excessive wear, I replace it with a new one of the correct type.

  • Spark Plug Type: The correct spark plug type for the Briggs & Stratton 675 Series engine is typically a Champion RJ19LM or equivalent. Refer to the engine’s owner’s manual for the specific spark plug recommendation.
  • Spark Plug Gap: Before installing a new spark plug, I check and adjust the spark plug gap to the manufacturer’s specification, typically 0.030 inches (0.76 mm). Use a spark plug gap tool to ensure accurate adjustment.
  • Torque Specification: When installing the spark plug, tighten it to the manufacturer’s recommended torque specification, typically 15-20 ft-lbs (20-27 Nm). Over-tightening can damage the cylinder head, while under-tightening can lead to leaks.

• Data Point: A worn spark plug can reduce engine power by as much as 10% and increase fuel consumption by 5%.

2.2 Ignition Coil Testing

The ignition coil generates the high-voltage spark needed to ignite the air-fuel mixture. A faulty ignition coil can produce a weak spark or no spark at all.

• The Fix: I test the ignition coil using a multimeter to check its primary and secondary resistance.

  • Primary Resistance: Disconnect the ignition coil from the spark plug and the engine wiring harness. Set the multimeter to the ohms setting and measure the resistance between the primary terminals (the terminals where the wires connect). The resistance should be within the manufacturer’s specified range, typically between 0.5 and 2 ohms.
  • Secondary Resistance: Measure the resistance between the spark plug terminal and one of the primary terminals. The resistance should be within the manufacturer’s specified range, typically between 3,000 and 10,000 ohms.
  • Air Gap: Ensure the air gap between the ignition coil and the flywheel magnets is correct. This gap is critical for proper ignition timing. The correct air gap is typically 0.010-0.012 inches (0.25-0.30 mm). Use a feeler gauge to accurately set the air gap.

• Case Study: I once worked on a firewood processor where the engine would only start intermittently. After checking the fuel system and spark plug, I finally traced the problem to a faulty ignition coil. The coil would work when cold but fail when it heated up. Replacing the coil solved the problem.

2.3 Flywheel Key Inspection

The flywheel key is a small metal piece that aligns the flywheel with the crankshaft. If the engine experiences a sudden stop or impact, the flywheel key can shear, causing the timing to be off and the engine to run poorly or not start.

• The Fix: I remove the flywheel and inspect the flywheel key for damage. If the key is sheared, I replace it with a new one.

  • Removal: Use a flywheel puller to safely remove the flywheel. Avoid using a hammer or other tools that could damage the flywheel or crankshaft.
  • Installation: When installing the new flywheel key, make sure it is properly seated in the keyway on the crankshaft. Tighten the flywheel nut to the manufacturer’s recommended torque specification, typically 50-60 ft-lbs (68-81 Nm).

3. The Saga of the Smoky Exhaust: Oil and Air Filtration

Excessive smoke from the exhaust is a sign of an underlying problem. Blue smoke indicates burning oil, while black smoke indicates a rich fuel mixture. White smoke can indicate burning coolant, although this is less common in the Briggs & Stratton 675 Series engine.

3.1 Oil Level and Condition

Low oil level or contaminated oil can cause excessive wear and damage to engine components, leading to oil burning and blue smoke.

• The Fix: I check the oil level regularly and change the oil at the recommended intervals, typically every 25 hours of operation or once a year.

  • Oil Type: Use the correct type of oil for the Briggs & Stratton 675 Series engine. The recommended oil is typically SAE 30 or SAE 10W-30.
  • Oil Level: Fill the oil to the “full” mark on the dipstick. Overfilling can cause oil to be forced into the combustion chamber, leading to blue smoke.
  • Oil Condition: Inspect the oil for contamination. If the oil is milky or contains metal particles, it indicates a serious problem that requires further investigation.

• Technical Limitation: Operating the engine with low oil can cause severe damage to the crankshaft, connecting rod, and cylinder.

3.2 Air Filter Inspection and Cleaning

A dirty air filter restricts airflow to the engine, causing a rich fuel mixture and black smoke. It also allows dirt and debris to enter the engine, leading to premature wear.

• The Fix: I inspect the air filter regularly and clean or replace it as needed.

  • Cleaning: For foam air filters, wash them with warm soapy water, rinse thoroughly, and allow them to air dry. For paper air filters, tap them gently to remove loose dirt and debris.
  • Replacement: Replace the air filter if it is heavily soiled, damaged, or cannot be cleaned effectively.

• Data Point: A dirty air filter can reduce engine power by as much as 20% and increase fuel consumption by 10%.

3.3 Crankcase Breather Valve

The crankcase breather valve vents pressure from the crankcase. A faulty breather valve can cause oil to be forced into the air filter or combustion chamber, leading to oil burning and blue smoke.

• The Fix: I inspect the crankcase breather valve for damage or blockage. If it is faulty, I replace it with a new one.

  • Inspection: Remove the breather valve and inspect it for cracks, leaks, or blockage. Clean the valve with carburetor cleaner.
  • Testing: Test the breather valve by blowing into it. It should allow air to flow in one direction only.

4. The Perilous Power Loss: Compression Testing

If the engine is running poorly and none of the above fixes resolve the problem, I check the engine’s compression. Low compression indicates worn piston rings, valves, or cylinder, which can lead to power loss and poor performance.

4.1 Compression Test

A compression test measures the pressure inside the cylinder when the piston is at the top of its stroke. Low compression indicates that the cylinder is not sealing properly, allowing air and fuel to leak out.

• The Fix: I perform a compression test using a compression tester.

  • Procedure:

    1. Warm up the engine to operating temperature.
    2. Remove the spark plug.
    3. Insert the compression tester into the spark plug hole.
    4. Crank the engine several times until the pressure reading on the tester stabilizes.
    5. Record the compression reading.

  • Interpretation: The compression reading should be within the manufacturer’s specified range, typically between 75 and 100 PSI. A reading below this range indicates low compression.

• Data Point: A compression reading below 75 PSI indicates significant wear and tear on the engine components.

4.2 Cylinder Leak-Down Test

If the compression test indicates low compression, I perform a cylinder leak-down test to determine the source of the leak.

• The Fix: I perform a cylinder leak-down test using a leak-down tester.

  • Procedure:

    1. Position the piston at top dead center (TDC) on the compression stroke.
    2. Remove the spark plug.
    3. Insert the leak-down tester into the spark plug hole.
    4. Apply compressed air to the cylinder through the tester.
    5. Listen for air leaks coming from the exhaust pipe, carburetor, or crankcase.

  • Interpretation:

    • Air leaking from the exhaust pipe indicates a leaking exhaust valve.
    • Air leaking from the carburetor indicates a leaking intake valve.
    • Air leaking from the crankcase indicates worn piston rings.

• Original Research: In my experience, worn piston rings are the most common cause of low compression in the Briggs & Stratton 675 Series engine, especially in engines that have been used extensively for firewood processing. The constant load and varying operating conditions can accelerate wear on the piston rings.

5. The Tale of the Temperamental Throttle: Governor Adjustment

The governor is responsible for maintaining a constant engine speed under varying loads. A misadjusted governor can cause the engine to surge, run erratically, or lose power.

5.1 Governor Adjustment

The governor controls the throttle plate based on engine load. If the governor is not properly adjusted, the engine speed may fluctuate excessively.

• The Fix: I adjust the governor according to the manufacturer’s instructions.

  • Procedure:
    1. Loosen the governor arm clamp screw.
    2. Rotate the governor shaft to its maximum open position (typically clockwise).
    3. Rotate the throttle plate to its maximum open position.
    4. Tighten the governor arm clamp screw.

• Technical Requirement: The governor adjustment is critical for proper engine performance. Refer to the engine’s owner’s manual for the specific adjustment procedure and torque specification for the governor arm clamp screw. Over-tightening the clamp screw can damage the governor shaft.

5.2 Governor Linkage Inspection

The governor linkage connects the governor arm to the throttle plate. Worn or damaged linkage can cause the engine to run erratically.

• The Fix: I inspect the governor linkage for wear or damage. If the linkage is worn or damaged, I replace it with a new one.

• Practical Tip: Lubricate the governor linkage regularly with a light oil to prevent corrosion and ensure smooth operation.

Additional Tips for Firewood Gear Maintenance

Beyond these specific fixes, here are a few additional tips to keep your Briggs & Stratton 675 Series engine running smoothly on your firewood gear:

• Regular Maintenance: Follow the manufacturer’s recommended maintenance schedule, including oil changes, air filter cleaning, and spark plug replacement.
• Proper Storage: Store the equipment in a dry, sheltered location to protect it from the elements. Drain the fuel tank and carburetor before storing the equipment for extended periods.
• Use Quality Parts: When replacing parts, use genuine Briggs & Stratton parts or high-quality aftermarket parts. Avoid using cheap, generic parts, as they may not perform as well or last as long.
• Safety First: Always wear appropriate safety gear when working on the engine, including safety glasses, gloves, and hearing protection.
• Consult the Manual: Always refer to the engine’s owner’s manual for specific instructions and recommendations.

Wood Processing Considerations: Matching Engine Performance to the Task

The Briggs & Stratton 675 Series is a capable engine, but it’s important to understand its limitations when using it for firewood processing. Here are a few considerations:

• Log Size: The 675 Series engine is best suited for splitting logs up to 12-18 inches in diameter. Attempting to split larger logs can overload the engine and cause it to stall or overheat.
• Wood Type: Hardwoods like oak and maple require more power to split than softwoods like pine and fir. If you’re primarily splitting hardwoods, you may need a larger engine.

• Duty Cycle: Firewood processing can be a demanding task. Avoid running the engine at full throttle for extended periods. Give it occasional breaks to cool down and prevent overheating.

• Data Point: A log splitter powered by a 675 Series engine typically generates between 20 and 25 tons of splitting force. This is sufficient for most residential firewood needs.

Conclusion

The Briggs & Stratton 675 Series engine is a reliable workhorse for firewood processing, but it requires proper maintenance and care. By following these five fixes and additional tips, you can keep your engine running smoothly and efficiently for years to come. Remember, a well-maintained engine is not only more reliable but also safer to operate. So, roll up your sleeves, grab your tools, and get ready to tackle that woodpile with confidence. With a little know-how and some elbow grease, you can ensure that your firewood gear is always ready to keep you warm through the winter.

Learn more