Bolens BL125 Leaf Blower Repair Tips (7 Expert Spark Fixes)

The crisp autumn air, the satisfying crackle of a wood-burning stove, the independence of providing your own heat – these are the things that draw many of us to firewood. But before you can bask in the warmth, there’s the often-overlooked task of leaf removal. That’s where leaf blowers come in, and when they fail, especially right at the start of leaf season, it can be incredibly frustrating. I remember one year, my own trusty leaf blower sputtered and died just as the maples were beginning to shed their vibrant leaves. It was a Bolens, not a BL125, but the principle is the same – a non-starting engine is a problem you need to solve quickly. That experience, and many since, has taught me a thing or two about diagnosing and fixing small engine problems, particularly those related to the spark system. This guide focuses on getting your Bolens BL125 leaf blower back in action, specifically targeting spark-related issues. We’ll go through expert fixes, step-by-step, and I’ll share some personal anecdotes and insights along the way. This isn’t just about fixing a leaf blower; it’s about understanding small engines and gaining the confidence to tackle similar problems in your other outdoor power equipment.

Bolens BL125 Leaf Blower Repair Tips: 7 Expert Spark Fixes

A leaf blower that won’t start is a common problem, and the spark system is often the culprit. A healthy spark is essential for igniting the fuel-air mixture in the engine. Without it, you’re just pulling the starter cord in vain. I’ll walk you through seven expert fixes that address the most common spark-related issues in the Bolens BL125. I’ll explain the “why” behind each step and share some troubleshooting tips based on my years of experience working with small engines.

1. The Spark Plug: Inspect, Clean, or Replace

The spark plug is the heart of the ignition system. It creates the spark that ignites the fuel-air mixture. Over time, spark plugs can become fouled with carbon deposits, oil, or fuel, which can prevent them from sparking properly.

Why this is important: A fouled spark plug is the most common reason for a no-start condition in small engines. It’s the first thing I check.
Step-by-step guide:
1. Safety first: Disconnect the spark plug wire from the spark plug. Never work on the ignition system with the wire connected, as you could get a shock.
2. Locate the spark plug: On the Bolens BL125, the spark plug is typically located on the side of the engine, near the cylinder head.
3. Remove the spark plug: Use a spark plug wrench (usually 13/16 inch or 5/8 inch, depending on the plug) to carefully unscrew the spark plug. Turn it counterclockwise.
4. Inspect the spark plug: Examine the electrode (the tip of the spark plug) for signs of fouling. Look for carbon buildup (black and sooty), oil (wet and greasy), or fuel (wet and smelling of gasoline). Also, check for any cracks or damage to the porcelain insulator.
5. Clean the spark plug (if applicable): If the spark plug is only lightly fouled with carbon, you can try cleaning it. Use a wire brush or a spark plug cleaner to remove the deposits. Be careful not to damage the electrode or the porcelain.
6. Check the spark plug gap: The spark plug gap is the distance between the electrode and the ground electrode. This gap is crucial for proper spark formation. The correct gap for the Bolens BL125 is typically around 0.030 inches (0.76 mm). Use a spark plug gap tool to measure and adjust the gap if necessary.
7. Replace the spark plug (if necessary): If the spark plug is heavily fouled, damaged, or if cleaning doesn’t improve its condition, it’s best to replace it. Use the correct spark plug for the Bolens BL125 (refer to your owner’s manual). A common replacement is Champion RJ19LM or equivalent.
8. Install the spark plug: Carefully screw the spark plug back into the engine, turning it clockwise. Tighten it snugly, but don’t overtighten it. The recommended torque is usually around 15-20 ft-lbs (20-27 Nm), but refer to your owner’s manual for the exact specification.
9. Reconnect the spark plug wire: Push the spark plug wire back onto the spark plug until it clicks into place.
Tools needed: Spark plug wrench, spark plug gap tool, wire brush or spark plug cleaner (optional).
Measurements: Spark plug gap: 0.030 inches (0.76 mm)
Personal story: I once spent hours trying to diagnose a starting problem on a chainsaw, only to discover it was a heavily fouled spark plug. A new spark plug solved the problem instantly. Now, I always check the spark plug first.
Strategic advantage: Regularly inspecting and replacing your spark plug can prevent many starting problems and ensure optimal engine performance.
Cost: Spark plugs are relatively inexpensive, typically costing between $5 and $10.
Skill level: Beginner

2. The Spark Plug Wire and Boot: Check for Continuity and Damage

The spark plug wire and boot connect the ignition coil to the spark plug. They carry the high-voltage electricity needed to create the spark. If the wire or boot is damaged, corroded, or loose, it can prevent the spark from reaching the spark plug.

Why this is important: A faulty spark plug wire or boot can interrupt the flow of electricity, resulting in a weak or nonexistent spark.
Step-by-step guide:
1. Safety first: Disconnect the spark plug wire from the spark plug.
2. Inspect the wire: Examine the spark plug wire for any signs of damage, such as cracks, cuts, or burns.
3. Inspect the boot: Check the spark plug boot for any cracks, tears, or looseness. Make sure it’s securely attached to both the spark plug and the spark plug wire.
4. Check for corrosion: Look for corrosion on the terminals of the spark plug wire and boot. Clean any corrosion with a wire brush or sandpaper.
5. Test for continuity: Use a multimeter to test the continuity of the spark plug wire. Set the multimeter to the “continuity” setting (usually indicated by a diode symbol or a speaker icon). Touch one probe of the multimeter to one end of the spark plug wire and the other probe to the other end. If the multimeter shows continuity (a beep or a low resistance reading), the wire is good. If it shows no continuity (no beep or a high resistance reading), the wire is broken and needs to be replaced.
6. Replace the wire or boot (if necessary): If the spark plug wire or boot is damaged, corroded, or fails the continuity test, replace it. You can purchase a new spark plug wire and boot assembly from an auto parts store or online retailer.
7. Install the new wire and boot: Connect the new spark plug wire to the ignition coil and the spark plug. Make sure the boot is securely attached to both ends.
Tools needed: Multimeter, wire brush or sandpaper (optional).
Measurements: Continuity test: should show a low resistance reading (near 0 ohms) for a good wire.
Personal story: I once had a leaf blower that would only start intermittently. After much troubleshooting, I discovered a tiny crack in the spark plug boot that was causing the spark to jump to ground. Replacing the boot solved the problem.
Strategic advantage: Regularly inspecting your spark plug wire and boot can prevent intermittent starting problems and ensure a strong, consistent spark.
Cost: Spark plug wires and boots are relatively inexpensive, typically costing between $10 and $20.
Skill level: Intermediate

3. The Ignition Coil: Test for Resistance and Output

The ignition coil is responsible for generating the high-voltage electricity needed to create the spark. It transforms the low-voltage electricity from the engine’s magneto into a high-voltage pulse that is sent to the spark plug. If the ignition coil is faulty, it may not be able to generate enough voltage to create a spark.

Why this is important: A faulty ignition coil is a common cause of no-start conditions in small engines. Testing the coil is crucial for determining if it’s the source of the problem.
Step-by-step guide:
1. Safety first: Disconnect the spark plug wire from the spark plug.
2. Locate the ignition coil: The ignition coil is typically located near the flywheel, under the engine cover. You may need to remove the engine cover to access it.
3. Disconnect the ignition coil wires: Disconnect the wires that connect the ignition coil to the engine.
4. Test for resistance: Use a multimeter to test the resistance of the ignition coil. You’ll need to consult your owner’s manual or a repair manual for the specific resistance values for the Bolens BL125. Typically, you’ll measure the primary resistance (between the coil’s terminals) and the secondary resistance (between one terminal and the spark plug wire connector).
5. Test for spark output: This test is a bit more involved and requires caution. Reconnect the spark plug wire to the ignition coil, but do not connect it to the spark plug. Hold the spark plug wire about 1/4 inch (6 mm) away from a metal part of the engine (ground). Pull the starter cord. You should see a strong, blue spark jumping from the spark plug wire to the engine. If you see a weak spark, a yellow spark, or no spark at all, the ignition coil is likely faulty.
6. Replace the ignition coil (if necessary): If the ignition coil fails the resistance test or the spark output test, replace it. You can purchase a new ignition coil from an auto parts store or online retailer.
7. Install the new ignition coil: Install the new ignition coil in the same location as the old one. Connect the wires and the spark plug wire.
8. Adjust the air gap: The air gap between the ignition coil and the flywheel is crucial for proper spark generation. Use a business card or a feeler gauge to set the air gap to the correct specification (typically around 0.010-0.015 inches or 0.25-0.38 mm). Loosen the mounting screws of the ignition coil, insert the business card or feeler gauge between the coil and the flywheel, and then tighten the screws. Remove the business card or feeler gauge.
Tools needed: Multimeter, business card or feeler gauge, screwdriver.
Measurements: Ignition coil resistance values (refer to your owner’s manual or a repair manual), air gap: 0.010-0.015 inches (0.25-0.38 mm)
Personal story: I once had a snowblower that wouldn’t start after sitting idle all summer. After testing the ignition coil, I discovered that it had completely failed. Replacing the coil brought the snowblower back to life.
Strategic advantage: Properly testing and replacing a faulty ignition coil can restore spark and get your engine running smoothly again.
Cost: Ignition coils typically cost between $20 and $50.
Skill level: Advanced

4. The Flywheel Key: Check for Shearing

The flywheel key is a small metal piece that connects the flywheel to the crankshaft. It ensures that the flywheel rotates in sync with the crankshaft. If the flywheel key is sheared (broken), the flywheel can slip, which can throw off the engine’s timing and prevent it from starting.

Why this is important: A sheared flywheel key is a less common, but still possible, cause of no-spark or weak-spark conditions. It’s often caused by a sudden stop or impact, such as hitting a rock with the leaf blower’s impeller.
Step-by-step guide:
1. Safety first: Disconnect the spark plug wire from the spark plug.
2. Remove the engine cover: You’ll need to remove the engine cover to access the flywheel.
3. Remove the flywheel nut: Use a socket wrench to remove the nut that holds the flywheel onto the crankshaft.
4. Remove the flywheel: You may need a flywheel puller to remove the flywheel. A flywheel puller is a tool that helps you remove the flywheel without damaging it.
5. Inspect the flywheel key: Once the flywheel is removed, inspect the flywheel key for signs of shearing. The key should be intact and fit snugly into the keyway on both the crankshaft and the flywheel. If the key is broken or damaged, it needs to be replaced.
6. Replace the flywheel key (if necessary): If the flywheel key is sheared, replace it with a new one. Make sure to use the correct flywheel key for the Bolens BL125.
7. Install the flywheel: Install the flywheel back onto the crankshaft, aligning the keyway on the flywheel with the keyway on the crankshaft.
8. Install the flywheel nut: Install the flywheel nut and tighten it to the correct torque specification (refer to your owner’s manual or a repair manual).
9. Reinstall the engine cover: Reinstall the engine cover.
Tools needed: Socket wrench, flywheel puller (optional), torque wrench.
Measurements: Flywheel nut torque specification (refer to your owner’s manual or a repair manual).
Personal story: I once spent hours troubleshooting a lawnmower that wouldn’t start. After checking everything else, I finally discovered that the flywheel key was sheared. Replacing the key solved the problem.
Strategic advantage: Checking and replacing a sheared flywheel key can restore proper engine timing and get your engine running smoothly again.
Cost: Flywheel keys are very inexpensive, typically costing only a few dollars. Flywheel pullers can range from $20-$50.
Skill level: Advanced

5. The Kill Switch: Check for Proper Function

The kill switch is a safety device that allows you to quickly stop the engine in an emergency. It works by grounding the ignition system, which prevents the spark plug from firing. If the kill switch is faulty or stuck in the “off” position, it can prevent the engine from starting.

Why this is important: A faulty kill switch can be a simple but easily overlooked cause of a no-start condition.
Step-by-step guide:
1. Safety first: Disconnect the spark plug wire from the spark plug.
2. Locate the kill switch: The kill switch is typically located on the handle of the leaf blower.
3. Inspect the kill switch: Examine the kill switch for any signs of damage or looseness.
4. Test the kill switch: Use a multimeter to test the kill switch. Set the multimeter to the “continuity” setting. With the kill switch in the “on” (run) position, the multimeter should show no continuity (no beep or a high resistance reading). With the kill switch in the “off” (stop) position, the multimeter should show continuity (a beep or a low resistance reading).
5. Disconnect the kill switch (for testing): If the kill switch is showing continuity in the “on” position, disconnect the wires from the kill switch. This will isolate the kill switch from the ignition system.
6. Try starting the engine: With the kill switch disconnected, try starting the engine. If the engine starts, the kill switch is faulty and needs to be replaced.
7. Replace the kill switch (if necessary): If the kill switch is faulty, replace it with a new one.
8. Reconnect the kill switch: Reconnect the wires to the new kill switch.
Tools needed: Multimeter.
Measurements: Continuity test: No continuity in the “on” position, continuity in the “off” position.
Personal story: I once spent hours troubleshooting a generator that wouldn’t start. After checking everything else, I finally discovered that the kill switch was stuck in the “off” position. A simple adjustment to the kill switch solved the problem.
Strategic advantage: Checking and replacing a faulty kill switch can quickly resolve a no-start condition.
Cost: Kill switches are relatively inexpensive, typically costing between $5 and $15.
Skill level: Intermediate

6. The Low Oil Sensor: Check for Proper Function (If Equipped)

Some Bolens BL125 leaf blowers are equipped with a low oil sensor. This sensor is designed to prevent the engine from running if the oil level is too low, which can damage the engine. If the low oil sensor is faulty, it can prevent the engine from starting, even if the oil level is actually adequate.

Why this is important: A faulty low oil sensor can be a source of frustration, as it can prevent the engine from starting even when everything else seems to be in order.
Step-by-step guide:
1. Safety first: Disconnect the spark plug wire from the spark plug.
2. Check the oil level: Make sure the oil level is at the correct level, according to your owner’s manual.
3. Locate the low oil sensor: The low oil sensor is typically located on the engine block, near the oil fill cap.
4. Disconnect the low oil sensor: Disconnect the wires from the low oil sensor.
5. Try starting the engine: With the low oil sensor disconnected, try starting the engine. If the engine starts, the low oil sensor is faulty and needs to be replaced.
6. Replace the low oil sensor (if necessary): If the low oil sensor is faulty, replace it with a new one.
7. Reconnect the low oil sensor: Reconnect the wires to the new low oil sensor.
Tools needed: None (unless you need to add oil).
Measurements: Oil level (refer to your owner’s manual).
Personal story: I once had a pressure washer that wouldn’t start. After checking everything else, I discovered that the low oil sensor was faulty. Disconnecting the sensor allowed the engine to start, and replacing the sensor solved the problem permanently.
Strategic advantage: Checking and replacing a faulty low oil sensor can resolve a no-start condition caused by a false low oil reading.
Cost: Low oil sensors typically cost between $10 and $25.
Skill level: Intermediate

7. The Wiring Harness: Inspect for Damage and Loose Connections

The wiring harness connects all of the electrical components in the engine, including the ignition coil, kill switch, and low oil sensor (if equipped). If the wiring harness is damaged or has loose connections, it can prevent the spark plug from firing.

Why this is important: A damaged wiring harness can interrupt the flow of electricity to the spark plug, resulting in a weak or nonexistent spark.
Step-by-step guide:
1. Safety first: Disconnect the spark plug wire from the spark plug.
2. Inspect the wiring harness: Examine the wiring harness for any signs of damage, such as cracks, cuts, or burns.
3. Check for loose connections: Check all of the connections in the wiring harness to make sure they are secure.
4. Clean any corroded connections: Clean any corroded connections with a wire brush or sandpaper.
5. Repair or replace the wiring harness (if necessary): If the wiring harness is damaged, you may be able to repair it by splicing the wires together. However, if the damage is extensive, it’s best to replace the entire wiring harness.
6. Reconnect the wiring harness: Reconnect all of the connections in the wiring harness.
Tools needed: Wire brush or sandpaper, wire strippers, wire connectors (if repairing).
Measurements: None.
Personal story: I once had a leaf blower that would only start intermittently. After much troubleshooting, I discovered a loose connection in the wiring harness. Tightening the connection solved the problem.
Strategic advantage: Inspecting and repairing or replacing a damaged wiring harness can restore proper electrical connections and get your engine running smoothly again.
Cost: The cost of repairing or replacing a wiring harness can vary depending on the extent of the damage and the availability of replacement parts. A new wiring harness can cost between $20 and $50.
Skill level: Advanced

These seven fixes cover the most common spark-related issues you’ll encounter with your Bolens BL125 leaf blower. Remember to always prioritize safety, consult your owner’s manual, and don’t be afraid to seek help from a qualified mechanic if you’re unsure about any of the steps. With a little patience and persistence, you can get your leaf blower back in action and tackle those autumn leaves with ease.

Beyond these specific fixes, there are a few general tips I can offer based on my experience:

Use fresh fuel: Old fuel can become stale and lose its ability to ignite properly. Always use fresh fuel that is less than 30 days old.
Use the correct fuel-oil mixture: The Bolens BL125 is a two-stroke engine, which means it requires a mixture of gasoline and oil. Use the correct fuel-oil mixture ratio, as specified in your owner’s manual. Typically, this is a 50:1 ratio (50 parts gasoline to 1 part oil).
Clean the air filter: A dirty air filter can restrict airflow to the engine, which can make it difficult to start. Clean the air filter regularly, according to your owner’s manual.
Store your leaf blower properly: When storing your leaf blower for extended periods, drain the fuel tank and carburetor to prevent fuel from gumming up the engine.

By following these tips and the expert fixes outlined above, you can keep your Bolens BL125 leaf blower running smoothly for years to come. Good luck, and happy leaf blowing!

Bolens BL125 Leaf Blower Repair Tips (7 Expert Spark Fixes)