Bolens Bl100 17 Cut 31Cc

I still remember the day I brought home my first Bolens BL100 string trimmer. After years of struggling with an underpowered electric model that couldn’t handle my unruly yard, I decided it was time for an upgrade. That was five years ago, and since then, my 17-inch cut, 31cc Bolens has become one of my most trusted yard tools. Through trial and error, countless maintenance sessions, and more than a few frustrating moments, I’ve learned everything there is to know about this reliable machine.

Whether you’re considering purchasing one, just brought it home, or are troubleshooting issues with your existing trimmer, I’m sharing my complete, hands-on experience with the Bolens BL100. From basic operation to advanced maintenance, this guide covers it all.

First Impressions and Assembly: Getting Started with Your Bolens BL100

When I first unboxed my Bolens BL100, I was immediately impressed by its sturdy construction. It definitely had more heft than my previous electric trimmer, but not so much that it felt unwieldy. The packaging was minimal but effective, and all parts were accounted for.

Assembly was straightforward, though I did have to reference the manual a couple of times. The main shaft components connect with a simple click-lock system, and attaching the guard shield was intuitive. The handle required a bit of adjustment to find the perfect balance point for my height (I’m 5’10”), but the process was painless with the included Allen wrench.

One thing to note: don’t throw away the manual after assembly! Unlike some tools where you can figure things out as you go, certain aspects of the Bolens BL100—particularly the fuel mixture and starting procedure—require specific knowledge that you’ll want to reference later.

The most important thing to remember when assembling your Bolens BL100 is to ensure the safety guard is properly installed before operation. This isn’t just a recommendation—it’s essential for preventing debris from flying toward you during use.

Understanding the Specs: What Makes the Bolens BL100 Tick

Before diving into operation, let’s talk specs. The Bolens BL100 is a gas-powered string trimmer featuring a 31cc 2-cycle engine. The “17-inch cut” in its name refers to its cutting swath—the diameter of the circle it cuts when in operation. This is a standard size that offers a good balance between efficiency (covering more ground with each pass) and maneuverability (not too unwieldy in tight spaces).

The trimmer weighs approximately 10 pounds when fully assembled and fueled, which is average for its class. I’ve found this weight to be manageable for sessions up to about an hour, though I definitely feel it in my arms after a full afternoon of yard work. The curved shaft design helps distribute this weight and makes it easier to navigate around obstacles like fence posts and garden beds.

One specification that isn’t immediately obvious but has proven crucial in my experience is the line diameter. The Bolens BL100 uses 0.095-inch diameter line, which strikes a nice balance between durability and cutting power. I’ve experimented with different line types over the years (more on that later), but understanding this baseline spec is important when purchasing replacements.

Fueling Up: The Right Mix for Optimal Performance

One of the first hurdles for new gas trimmer owners is getting the fuel mixture right. The Bolens BL100 uses a specific fuel-to-oil ratio that’s essential for proper operation and longevity of the engine.

The correct mixture is 40:1—that’s 40 parts gasoline to 1 part 2-cycle engine oil. In practical terms, this means adding 3.2 ounces of oil to each gallon of gasoline. I learned the hard way that this ratio isn’t just a suggestion; using incorrect mixtures can lead to poor performance, excessive smoke, or even engine damage.

I recommend using fresh, unleaded gasoline with an octane rating of 87 or higher. For the oil component, stick with quality 2-cycle oil specifically formulated for air-cooled engines. During my first year of ownership, I tried to save a few dollars by using generic oil, and the difference in performance was noticeable—more smoke, harder starting, and less power.

Pro tip: I mix my fuel in small batches (typically 1 gallon at a time) and store it in a dedicated gas can clearly marked “Trimmer Fuel Mix.” This prevents mix-ups and ensures the fuel doesn’t sit for too long, as gas-oil mixtures can degrade over time. I never use fuel that’s more than 30 days old, as it can lead to starting issues and gummed-up carburetors.

Starting Your Bolens BL100: The Right Sequence Makes All the Difference

Starting a gas trimmer like the Bolens BL100 follows a specific sequence, and knowing this process can save you a lot of frustration. I’ve refined my starting technique over the years, and here’s what works consistently:

1. Place the trimmer on flat ground
2. Set the on/off switch to the “ON” position
3. Press the primer bulb 7-10 times until you see fuel in the clear return line
4. Set the choke to the fully closed position (usually marked “CHOKE”)
5. Hold the throttle trigger and lock it in the start position
6. Pull the starter cord firmly until you hear the engine attempt to start (usually 3-5 pulls)
7. Once it attempts to start, move the choke to the half-open position
8. Pull the starter cord again until the engine runs
9. Allow the engine to warm up for 30-60 seconds
10. Move the choke to the “RUN” position and release the throttle lock

This sequence works about 95% of the time for my trimmer, even after winter storage. The most common mistake I made when I first got my Bolens was not priming it enough—those 7-10 pumps of the primer bulb are critical for getting fuel into the carburetor.

If you’re having trouble starting your Bolens BL100, don’t immediately assume something is wrong with the machine. Nine times out of ten, starting issues are related to improper fuel mixture, old fuel, or not following the starting sequence correctly. I’ve had many moments of frustration only to realize I simply forgot to turn the switch to “ON” or didn’t prime it enough.

Operating Your Trimmer: Techniques for Efficient Cutting

Once your Bolens BL100 is running, operating it effectively takes some practice. Over the years, I’ve developed techniques that maximize cutting efficiency while minimizing fatigue.

For standard grass trimming, I hold the trimmer so that the cutting head is slightly tilted toward the area being cut. The optimal cutting zone is at the tip of the line, not the full diameter. Using just the tip provides cleaner cuts and extends line life. I typically operate the trimmer at about 3/4 throttle for regular grass, which balances cutting power with fuel efficiency and noise.

For edging along sidewalks or driveways, I rotate the trimmer so that the cutting head is vertical, with the guard shield facing me. This creates a clean, defined edge. For this operation, I typically use full throttle for maximum cutting power.

When tackling tall weeds or brush, I use a scything motion—sweeping the trimmer from right to left, then back—and let the cutting line do the work rather than forcing it through tough vegetation. This prevents bogging down the engine and reduces line breakage.

A technique I wish I’d learned earlier is “tapering” around obstacles like trees. By gradually reducing throttle as you approach the tree trunk and holding the trimmer at a slight angle, you can trim very close to the bark without damaging it. This eliminates the need for follow-up work with hand trimmers.

Line Replacement and Management: The Ongoing Maintenance Task

If there’s one task you’ll perform more than any other with your Bolens BL100, it’s replacing the cutting line. The bump-feed system on this trimmer is fairly standard but has a few quirks worth noting.

To replace the string on a Bolens BL100:

1. Turn off the trimmer and disconnect the spark plug for safety
2. Press in the tabs on the sides of the trimmer head and remove the cover
3. Remove any remaining line from the spool
4. Prepare approximately 15-20 feet of 0.095″ diameter line
5. Find the midpoint of your new line and hook it into the notch in the center divider of the spool
6. Wind each half of the line in opposite directions, following the arrows on the spool
7. Keep the line taut as you wind to prevent tangling
8. When about 6 inches of line remains on each end, snap them into the holding slots on the spool
9. Feed the line ends through the eyelets in the trimmer head
10. Replace the spool into the housing and reattach the cover, ensuring the tabs click into place

I’ve found that the quality of line makes a tremendous difference in performance. After experimenting with various brands and types, I’ve settled on a commercial-grade twisted line that offers excellent durability without being so thick that it strains the engine. While the Bolens is designed for 0.095″ line, I’ve successfully used 0.105″ in particularly tough areas, though I wouldn’t recommend going thicker than that.

The bump-feed system on the Bolens works by tapping the trimmer head against the ground while the engine is running at full throttle. This releases a small amount of line. It took me some practice to get the right “bump” technique—too gentle and the line won’t advance, too hard and you risk damaging the head. A firm tap on grass or soft dirt works best.

One modification I’ve made to improve line management is pre-cutting several lengths of line and storing them in a small container attached to my trimmer with zip ties. This way, I always have replacement line on hand without carrying the entire spool.

Troubleshooting Common Issues: When Your Bolens BL100 Won’t Cooperate

Even the most reliable tools have their off days, and the Bolens BL100 is no exception. Over my years of ownership, I’ve encountered and resolved numerous issues. Here are the most common problems and their solutions:

Trimmer Won’t Start

This is the most common issue, and I follow a systematic approach to diagnosing it:

1. Check the fuel level and mixture ratio
2. Examine the spark plug for fouling or damage
3. Verify that the air filter is clean
4. Ensure the fuel filter in the tank isn’t clogged
5. Confirm that the spark arrestor screen isn’t blocked with carbon deposits

In about 80% of cases, starting issues are related to fuel problems—either old fuel, improper mixture, or water contamination. I now make it a habit to drain the fuel system completely if the trimmer will sit unused for more than a month.

Engine Starts But Stalls

If your Bolens starts but won’t keep running, the most likely culprits are:

1. Clogged air filter (I clean mine every 10 hours of operation)
2. Partially blocked fuel line or filter
3. Improperly adjusted carburetor
4. Exhaust port or muffler clogged with carbon deposits

I’ve found that cleaning the air filter and checking the fuel system solves this issue most of the time. For carburetor adjustments, consult the manual—improper adjustments can damage the engine.

Line Won’t Feed or Advance

Line feeding problems usually come down to:

1. Improperly wound spool (follow the directional arrows!)
2. Line tangled inside the spool
3. Dirt or debris preventing the bump mechanism from working
4. Worn bump knob or internal spring

I’ve learned to wind the spool meticulously, keeping tension on the line throughout the process. This prevents the frustrating tangles that can render your trimmer useless mid-job.

Engine Lacks Power

If your trimmer is running but seems underpowered:

1. Check for a partially clogged air filter
2. Examine the spark arrestor screen for blockage
3. Verify the fuel mixture is correct
4. Ensure the exhaust port isn’t restricted by carbon buildup

I once spent weeks wondering why my trimmer seemed to be losing power, only to discover that the spark arrestor screen was almost completely blocked. Cleaning it restored full power immediately.

Maintenance Schedule: Keeping Your Bolens BL100 in Prime Condition

Preventative maintenance is the key to longevity with any gas-powered tool. Based on my experience, here’s the maintenance schedule I follow for my Bolens BL100:

After Each Use:

• Clean debris from the cutting head and cooling fins
• Check for loose fasteners and tighten as needed
• Inspect the cutting line and replace if necessary
• Wipe down the entire unit, focusing on air intake areas

Every 10 Hours of Operation:

• Clean or replace the air filter
• Inspect and clean the spark plug
• Check the fuel filter for contamination
• Lubricate the gearbox with high-temperature grease

Every 25 Hours of Operation:

• Replace the spark plug
• Clean the exhaust port and spark arrestor screen
• Check the fuel lines for cracks or damage
• Inspect the starter mechanism and clean as needed

Seasonal Maintenance (Before Storage):

• Drain all fuel from the tank and run the engine until it stops
• Remove and clean the spark plug, then add a drop of oil to the cylinder
• Clean all external surfaces thoroughly
• Store in a dry, dust-free location

This maintenance schedule has kept my Bolens running reliably for years. The most critical aspects are keeping the air filter clean and properly managing the fuel system. I’ve learned that an hour of maintenance prevents days of frustration from breakdowns.

Replacement Parts: Where to Find Them and Which Ones Matter

Eventually, even with proper maintenance, parts wear out and need replacement. For the Bolens BL100, I’ve found several reliable sources for genuine and aftermarket parts.

Hardware stores like Home Depot and Lowe’s often carry common replacement parts such as air filters, spark plugs, and trimmer line. For more specific components, online retailers specializing in outdoor power equipment offer comprehensive inventories.

The most frequently replaced parts for my Bolens have been:

1. Air filter (about once per season)
2. Spark plug (annually)
3. Fuel filter (every other season)
4. Trimmer head or components (every 2-3 years, depending on use)
5. Starter rope (replaced once in five years)

When selecting replacement parts, I’ve learned that genuine parts are worth the extra cost for critical components like the carburetor or ignition module. For maintenance items like filters, quality aftermarket options work just as well at a lower price point.

One replacement part strategy I’ve adopted is purchasing certain consumables in bulk when they’re on sale. Items like air filters and spark plugs don’t degrade in storage, and having them on hand means I’m never caught without a critical part during trimming season.

Safety Considerations: Protecting Yourself and Others

Operating a gas-powered string trimmer involves certain risks, and safety should always be your priority. Here are the safety practices I’ve adopted after years of using my Bolens BL100:

Personal Protective Equipment:

• Safety glasses or a face shield (non-negotiable—I’ve had debris fly back at surprising speeds)
• Ear protection (the 31cc engine operates at around 96 decibels)
• Long pants and closed-toe shoes
• Gloves for better grip and vibration reduction

Operational Safety:

• Always inspect the work area for hidden objects like rocks, wire, or toys
• Maintain awareness of people and pets—I maintain at least a 50-foot safety zone
• Never operate in wet conditions or during thunderstorms
• Keep both hands on the handles during operation
• Turn off the engine when not actively trimming

Maintenance Safety:

• Always disconnect the spark plug before performing any maintenance
• Allow the engine to cool completely before refueling
• Perform maintenance in a well-ventilated area
• Properly dispose of used oil and fuel

I learned some of these safety practices the hard way. During my first month of ownership, I was trimming in shorts and caught a small stone that left a bruise on my calf for weeks. Since then, I’ve been religious about wearing appropriate protective gear.

Winter Storage: Preserving Your Investment During the Off-Season

Proper storage during the winter months is crucial for ensuring your Bolens BL100 starts up reliably when spring arrives. My end-of-season storage routine includes:

1. Running the engine until it’s completely out of fuel, or using a fuel stabilizer if you prefer to leave fuel in the tank
2. Removing and cleaning the spark plug, then adding a few drops of engine oil into the cylinder
3. Pulling the starter cord slowly to distribute the oil, then reinstalling the spark plug
4. Cleaning the entire unit thoroughly, paying special attention to cooling fins and air intakes
5. Removing the trimmer line from the head to prevent it from taking a set
6. Applying a light coat of oil to metal parts to prevent rust
7. Storing in a dry, climate-controlled space if possible

I made the mistake of skipping proper storage procedures my first year and paid for it with difficult starting and poor performance the following spring. Now, I treat end-of-season storage as seriously as any maintenance task.

Is the Bolens BL100 Right for Your Needs? Honest Assessment

After five years with my Bolens BL100, I can offer an honest assessment of its strengths and limitations.

Strengths:

• Reliable starting when properly maintained
• Adequate power for typical residential trimming tasks
• Reasonable fuel efficiency for a 31cc engine
• Durable construction that holds up to regular use
• Relatively lightweight compared to professional models

Limitations:

• Not ideal for heavy-duty brush clearing or very large properties
• Vibration can cause fatigue during extended use
• Louder than electric alternatives
• Requires more maintenance than battery-powered options
• Limited to 0.095″ line (though 0.105″ works in a pinch)

For typical suburban yards under an acre, the Bolens BL100 offers an excellent balance of power, weight, and cost. I’ve found it more than capable of handling my 3/4-acre property with mixed terrain.

However, if you have extensive heavy brush to clear or very precise edging requirements, you might consider either a more powerful brush cutter or a dedicated edging tool to complement the Bolens.

Final Thoughts: Why the Bolens BL100 Remains in My Tool Arsenal

After five years and countless hours of use, my Bolens BL100 continues to be a reliable workhorse in my lawn care arsenal. While I’ve added other specialized tools over the years, the Bolens remains my go-to for general trimming tasks.

What I appreciate most is its predictability—with proper maintenance and care, it starts reliably and performs consistently. The bump-feed system, while occasionally finicky, is simple enough that field repairs are straightforward. The curved shaft design reduces fatigue during extended use, and the 17-inch cutting swath strikes a perfect balance between efficiency and maneuverability.

If you’re in the market for a dependable gas string trimmer that won’t break the bank, the Bolens BL100 17-inch cut with its 31cc engine deserves serious consideration. It’s not the fanciest or most powerful trimmer on the market, but it delivers where it counts: reliable performance at a reasonable price point.

Remember that any gas-powered tool is only as good as the maintenance it receives. Commit to regular upkeep, use the correct fuel mixture, and your Bolens BL100 will likely provide years of trustworthy service, just as mine has.

Whether you’re tackling your first home’s yard care or looking to upgrade from an underpowered electric model, the Bolens BL100 offers a compelling combination of features that make it worth a spot in your shed. Just be prepared to develop a relationship with this tool—understand its quirks, maintain it properly, and it will serve you well through many seasons of growth.