If you own a Honda GCV160 engine—whether it’s powering your lawn mower, pressure washer, or generator—you already know how reliable and efficient this little workhorse can be. But when you start noticing gas leaking around the spark plug area, it’s not just a minor inconvenience. It’s a red flag that something is off, and more often than not, the culprit isn’t the spark plug itself, but rather a failing seal, worn gasket, or incorrect installation. However, replacing the spark plug during troubleshooting is a smart, proactive step—especially since a faulty or mismatched plug can exacerbate fuel system issues, poor combustion, and even contribute to fuel leaks over time.
This guide exists because too many homeowners and DIY mechanics jump straight to replacing parts without understanding the root cause or knowing what to look for in a quality replacement. The GCV160 is a precision-engineered engine, and using the wrong spark plug—or installing one improperly—can lead to poor performance, hard starts, reduced fuel efficiency, and yes, even fuel leakage due to improper sealing or combustion pressure imbalances. Our goal here is to cut through the confusion, eliminate guesswork, and give you the expert-level knowledge needed to choose the best possible spark plug for your GCV160—whether you’re fixing a gas leak, performing routine maintenance, or upgrading for better performance.
By the end of this comprehensive buying guide, you’ll understand exactly what makes a spark plug suitable (or unsuitable) for the Honda GCV160 engine. You’ll learn how to identify high-quality components, avoid common pitfalls, interpret technical specs like heat range and electrode design, and make a confident purchase decision—even if you’ve never touched a wrench before. We’ll also cover budget considerations, brand comparisons, installation tips, and how to differentiate between a true spark plug issue and other causes of gas leakage. Whether you’re a weekend warrior or a seasoned technician, this guide will equip you with everything needed to keep your GCV160 running smoothly, safely, and leak-free.
What to Look for When Buying Buying Guide
1. Correct Thread Size and Reach
One of the most critical—and often overlooked—factors when selecting a replacement spark plug for the Honda GCV160 is ensuring the thread size and reach (also called “reach length” or “seat length”) match OEM specifications exactly. The GCV160 uses a 14mm thread diameter with a 19mm reach and a 26.5mm hex size. Installing a plug with incorrect reach can cause serious problems: if it’s too short, the electrode won’t protrude far enough into the combustion chamber, leading to poor ignition and carbon buildup. If it’s too long, the electrode can physically contact the piston or valves, resulting in catastrophic engine damage.
Always verify these dimensions before purchasing. Many aftermarket plugs claim compatibility with Honda small engines, but subtle differences in reach can slip through. For example, some universal-fit plugs may list “fits Honda GCV160” but actually have a 12mm or 20mm reach—both of which are wrong. Always cross-reference the part number with Honda’s official service manual or trusted OEM cross-reference charts. When in doubt, measure your old plug or consult a certified Honda dealer.
2. Heat Range Compatibility
The heat range of a spark plug determines how well it dissipates heat from the combustion chamber to the engine head. The GCV160 is designed to operate optimally with a specific heat range—typically a “hot” plug for continuous light-duty use (like mowing) or a “cold” plug for high-load, high-RPM applications. Most OEM Honda GCV160 engines use a medium-to-hot heat range plug (often equivalent to NGK BPR6ES or BPR5ES, depending on model year and application).
Using a plug with the wrong heat range can lead to pre-ignition (if too cold), fouling (if too hot), or incomplete combustion—all of which increase fuel consumption and may contribute to vapor lock or fuel seepage near the plug well. For instance, a colder plug in a mower used for extended periods in hot weather might not get hot enough to burn off carbon deposits, leading to misfires and potential fuel dilution in the crankcase. Conversely, a hotter plug in a pressure washer running at high RPMs could overheat and cause detonation.
Always match the heat range specified in your owner’s manual. If you’ve modified your engine (e.g., added a performance air filter or exhaust), consider consulting a small engine specialist to determine if a different heat range is warranted.
3. Electrode Material and Design
Spark plug electrodes come in various materials—copper, nickel alloy, platinum, and iridium—each offering different levels of durability, conductivity, and cost. For the GCV160, which operates under moderate stress and doesn’t require extreme performance, a standard nickel-alloy or copper-core plug is usually sufficient. However, premium options like platinum or iridium can offer longer service life and more consistent spark delivery.
Copper-core plugs (like the NGK BPR6ES) are excellent conductors and provide strong sparks, making them ideal for older engines or those with weaker ignition systems. They’re also typically the most affordable. Platinum plugs (e.g., Denso PK20PR-P8) last longer and resist erosion better, while iridium plugs (such as NGK Iridium IX series) offer the longest lifespan and finest electrode tips for precise ignition—though they come at a higher price point.
For most GCV160 users, a quality copper or nickel plug will perform flawlessly and last 2–3 seasons with proper maintenance. Only consider platinum or iridium if you prioritize longevity over upfront cost or operate in harsh conditions (e.g., dusty environments, frequent starts/stops).
4. Gap Specification
The spark plug gap—the distance between the center and ground electrodes—must be set correctly for optimal combustion. The Honda GCV160 typically requires a gap of 0.028 inches (0.7mm), though some models may specify 0.030 inches (0.8mm). Always check your owner’s manual or the emissions label under the hood.
An incorrect gap can cause hard starting, misfires, rough idling, and increased fuel consumption. A gap that’s too narrow produces a weak spark, while one that’s too wide may exceed the ignition system’s capacity to fire consistently, especially as the coil ages. Never assume a new plug comes pre-gapped correctly—many aftermarket plugs ship with factory settings that may not match your engine’s requirements.
Use a wire-type gap tool (not a coin-style feeler gauge) to measure and adjust the gap. Coin gauges can bend the delicate ground electrode, altering the gap unpredictably. If you’re replacing multiple plugs or performing seasonal maintenance, it’s worth investing in a dedicated gap tool.
5. Sealing Washer and Gasket Integrity
Since your primary concern involves gas leaking around the spark plug, the sealing mechanism is paramount. The GCV160 uses a tapered seat design (not a gasketed seat), meaning the plug seals via metal-to-metal contact between the plug’s taper and the cylinder head. However, some aftermarket plugs include an integrated crush washer or reusable gasket, which can interfere with proper sealing if not designed correctly.
A compromised seal allows combustion gases—and sometimes fuel vapors—to escape, creating the appearance of a gas leak. In reality, it’s often pressurized vapor or oil mist being forced out, which can condense and look like liquid fuel. Always ensure the replacement plug has a clean, undamaged taper seat and that the cylinder head threads are free of debris or carbon buildup before installation.
Additionally, never reuse an old crush washer if your plug includes one. Always install with a new, properly sized washer to ensure a tight seal. Over-tightening can distort the washer or crack the cylinder head, while under-tightening leads to leaks.
6. Brand Reputation and OEM Compatibility
Not all spark plugs are created equal—even if they look identical. Stick with reputable brands known for small engine reliability: NGK, Denso, Champion, and Bosch are top-tier choices. Honda OEM plugs (often rebranded NGK or Denso units) are always a safe bet, but high-quality aftermarket equivalents can offer equal or better performance at a lower price.
Avoid no-name or ultra-cheap plugs from unknown manufacturers. These often use inferior materials, inconsistent tolerances, and poor-quality electrodes that erode quickly or fail to seal properly. A failing plug can cause misfires that increase crankcase pressure, potentially forcing fuel past seals and gaskets—exacerbating your original leak issue.
Cross-referencing is key. For example, the Honda 98079-56846 plug is equivalent to NGK BPR6ES or Denso W20EPR-U. Use trusted cross-reference tools from NGK or Denso’s websites to confirm compatibility.
7. Warranty and Support
While spark plugs are consumable items, reputable brands often back their products with limited warranties against manufacturing defects. NGK, for instance, offers a 1-year warranty on its automotive and small engine plugs. This won’t cover normal wear, but it protects against premature failure due to material flaws.
More importantly, consider the availability of customer support. If you install a plug and still experience leaks or performance issues, being able to contact the manufacturer for guidance can save time and money. Avoid sellers or brands with no return policy or customer service presence.
8. Ease of Installation and Tool Requirements
The GCV160’s spark plug is generally accessible, but tight engine compartments (especially on walk-behind mowers) can make removal tricky. Choose a plug that doesn’t require specialized tools beyond a standard spark plug socket (usually 13/16″ or 21mm) and ratchet.
Some premium plugs come with anti-seize coating or nickel-plated threads to prevent galling, which is helpful if you live in a humid or salty environment. However, avoid applying additional anti-seize unless specified by the manufacturer—it can alter torque specifications and lead to over-tightening.
Also, consider whether the plug comes with a built-in resistor. Most modern small engines, including the GCV160, use resistor-type plugs to suppress electromagnetic interference (EMI) that can affect onboard electronics or nearby radios. Non-resistor plugs may cause static or erratic behavior in sensitive equipment.
Different Types of Buying Guide
Common Buying Mistakes to Avoid
❌ Mistake: Assuming All “Honda-Compatible” Plugs Are Equal
Why it’s bad: Many retailers label generic plugs as “fits Honda GCV160,” but subtle differences in thread pitch, reach, or seat design can cause leaks, poor performance, or engine damage. A plug that looks identical may have a 0.5mm shorter reach, preventing proper combustion chamber penetration.
What to do instead: Always verify the exact part number against Honda’s official cross-reference list. Stick to NGK BPR6ES, Denso W20EPR-U, or Honda 98079-56846 equivalents. When in doubt, buy OEM or from a trusted small engine parts supplier.
❌ Mistake: Ignoring the Spark Plug Gap
Why it’s bad: A misgapped plug causes weak sparks, misfires, and increased fuel consumption. Over time, this can lead to unburned fuel washing down cylinder walls, diluting oil, and increasing crankcase pressure—potentially forcing fuel past seals and creating apparent leaks.
What to do instead: Always check and adjust the gap before installation. Use a wire gap tool and set to 0.028–0.030 inches as specified. Never assume pre-gapped plugs are correct.
❌ Mistake: Reusing Old Washers or Over-Tightening
Why it’s bad: Reusing a crush washer prevents proper sealing, while over-tightening can crack the cylinder head or strip threads—both leading to gas or vapor leaks around the plug base.
What to do instead: Always install with a new crush washer (if applicable) and torque to Honda’s specification (typically 13–17 ft-lbs). Use a torque wrench if possible. Hand-tighten first, then give a slight additional turn—never force it.
❌ Mistake: Choosing Based Solely on Price
Why it’s bad: Ultra-cheap plugs often use inferior materials that erode quickly, foul easily, or fail to seal. This leads to repeated replacements, poor engine performance, and can mask or worsen underlying issues like fuel leaks.
What to do instead: Invest in a quality plug from a reputable brand. The difference between a $2 and $8 plug is minimal compared to the cost of engine repair or downtime.
❌ Mistake: Confusing Fuel Leak Causes
Why it’s bad: Gas leaking near the spark plug isn’t always due to the plug itself. It could be a cracked plug well, degraded crankcase gasket, or carburetor overflow. Replacing the plug without diagnosing the root cause wastes time and money.
What to do instead: Inspect the area thoroughly. Wipe clean, run the engine, and observe. If fuel pools near the plug base, check for cracks in the cylinder head or worn valve seals. Address the underlying issue alongside plug replacement.
❌ Mistake: Using Automotive Spark Plugs
Why it’s bad: Car spark plugs are designed for higher compression, different heat ranges, and longer reach. Installing one in a GCV160 can cause piston contact, pre-ignition, or sealing failure.
What to do instead: Only use plugs specifically rated for small engines or lawn equipment. Verify compatibility with your exact engine model.
❌ Mistake: Skipping Routine Maintenance
Why it’s bad: A new spark plug won’t fix chronic issues caused by dirty air filters, old fuel, or clogged carburetors. These can lead to rich running conditions that flood the plug and increase leak risks.
What to do instead: Replace the plug as part of a full tune-up: clean or replace air filter, drain old fuel, inspect carburetor, and check valve clearance if applicable.
Budget Guidelines: How Much Should You Spend?
– Entry-Level ($1–$3): These are typically no-name or generic universal plugs. While they may work in a pinch, expect shorter lifespan (1 season or less), inconsistent gaps, and potential sealing issues. Best reserved for emergency field repairs or very infrequent use.
– Mid-Range ($4–$8): This is the sweet spot for most GCV160 owners. Brands like NGK (BPR6ES), Champion (RJ19LM), or Denso (W20EPR-U) offer reliable performance, correct specs, and 2–3 seasons of service. Excellent value for money and widely available at hardware stores or online.
– Premium ($9–$15): Includes platinum or iridium plugs from top brands (e.g., NGK Iridium IX, Denso Iridium Power). Ideal for users who want maximum longevity, consistent performance in varying conditions, and reduced maintenance frequency. Worth the investment if you use your equipment weekly or in dusty/hot environments.
– Luxury ($16+): High-end iridium or double-platinum plugs with advanced features like fine-wire electrodes or laser-welded tips. Overkill for most residential GCV160 applications but may appeal to collectors, restorers, or commercial users with fleets of equipment.
Expert Tips for Getting the Best Deal
– Shop During Off-Season: Late fall and winter are ideal times to buy small engine parts. Retailers often discount lawn care items before spring, so you can stock up on plugs, filters, and oil at lower prices.
– Compare Online vs. Local: Big-box stores (Home Depot, Lowe’s) often carry basic NGK or Champion plugs at competitive prices. However, online retailers (Amazon, Jack’s Small Engines, PartsTree) frequently offer better selection, user reviews, and bundle deals. Check shipping costs—sometimes local pickup is cheaper.
– Look for OEM Cross-Reference Tools: Use NGK’s or Denso’s official cross-reference databases to find exact equivalents. This ensures compatibility and often reveals cheaper alternatives to Honda genuine parts.
– Check Return Policies: Even if a plug is the right part number, manufacturing defects happen. Buy from sellers with hassle-free returns (e.g., Amazon, Walmart) so you can swap it out if needed.
– Inspect Before Installing: Open the package and visually inspect the plug. Look for cracks in the insulator, bent electrodes, or damaged threads. Don’t install a questionable plug—even if it’s new.
– Combine with Other Maintenance: Many online retailers offer discounts when you buy spark plugs, air filters, and oil together. This saves money and ensures you’re doing a complete tune-up.
– Join Loyalty Programs: Stores like Tractor Supply Co. or local lawn equipment dealers often have loyalty programs that offer member pricing or rebates on small engine parts.
– Read Recent Reviews: Product formulations can change. A plug that was great two years ago might have quality issues now. Check the most recent 10–20 reviews for consistency.
Frequently Asked Questions
Q: Can a bad spark plug cause gas to leak from the engine?
A: Not directly—but indirectly, yes. A misfiring or fouled plug can cause incomplete combustion, leading to fuel washing down cylinder walls and increasing crankcase pressure. This pressure can force fuel vapors past seals and gaskets, creating the appearance of a leak near the spark plug. Additionally, an improperly seated or damaged plug can allow combustion gases to escape, which may carry fuel vapor with it.
Q: How often should I replace the spark plug in my GCV160?
A: Honda recommends replacing the spark plug every 100 hours of operation or annually, whichever comes first. For typical homeowner use (10–20 hours per year), this means replacing it every 2–3 seasons. If you notice hard starting, rough idle, or reduced power, inspect the plug sooner.
Q: Is it safe to use a non-resistor spark plug in my GCV160?
A: Generally not recommended. The GCV160 uses a resistor-type plug to reduce electromagnetic interference, which can affect onboard electronics or nearby radios. Non-resistor plugs may cause static or erratic behavior in sensitive equipment. Always use a resistor plug unless specified otherwise.
Q: Can I clean and reuse an old spark plug?
A: You can clean a mildly fouled plug with a wire brush or plug cleaner, but it’s not advisable for long-term reliability. Electrodes erode over time, and the insulator can develop micro-cracks. For best performance and to avoid future issues, replace rather than reuse.
Q: Why is my new spark plug still leaking gas?
A: If gas continues to leak after plug replacement, the issue likely isn’t the plug. Check for: a cracked cylinder head around the plug well, a damaged crankcase gasket, carburetor float needle sticking open, or excessive crankcase pressure due to worn piston rings. A compression test can help diagnose internal engine issues.
Q: What’s the difference between BPR6ES and BPR5ES?
A: The number indicates the heat range: “6” is hotter than “5.” The GCV160 typically uses BPR6ES (hotter) for normal operation. Using BPR5ES (colder) may be appropriate only if the engine runs at very high loads or RPMs continuously, such as in commercial pressure washing. Stick with BPR6ES unless advised otherwise.
Q: Do I need to apply anti-seize to the spark plug threads?
A: Honda does not recommend anti-seize on spark plugs for the GCV160. The threads are designed to be installed dry. Anti-seize can alter torque values and lead to over-tightening, which risks damaging the aluminum cylinder head. If corrosion is a concern in your area, use a nickel-based anti-seize sparingly—but only if specified by the plug manufacturer.
Q: Can I use an automotive spark plug in my lawn mower?
A: No. Automotive plugs have different thread lengths, heat ranges, and seat designs. Installing one can cause piston contact, poor sealing, or incorrect combustion characteristics. Always use a small engine-specific plug.
Q: How do I know if my spark plug is the right heat range?
A: After running the engine under normal load for 10–15 minutes, remove the plug. The insulator tip should be light gray or tan. If it’s white or blistered, the plug is too hot. If it’s black and sooty, it’s too cold. A properly gapped, correct heat range plug will show moderate carbon buildup without glazing or melting.
Q: Where can I find the official Honda part number for my GCV160 spark plug?
A: Check your owner’s manual, the emissions label under the engine shroud, or visit Honda’s official parts website (partshouse.com) and enter your model and serial number. The OEM part number is typically 98079-56846.
Our Final Recommendations
– Best for Budget-Conscious Buyers: NGK BPR6ES – At around $4–$6, this copper-core plug offers OEM-level performance, correct specs, and reliable ignition. Widely available and trusted by professionals.
– Best Overall Value: Denso W20EPR-U – Slightly more durable than standard copper plugs with excellent heat dissipation. Priced under $8, it’s a great balance of cost, longevity, and performance.
– Best Premium Option: NGK Iridium IX BPR6EIX – Features a fine-wire iridium center electrode for ultra-precise spark and up to 4x longer life than copper. Ideal for frequent users or harsh conditions. Priced around $12–$15.
– Best for Beginners: Champion RJ19LM – Simple, affordable, and easy to find at most hardware stores. Comes pre-gapped and works flawlessly in unmodified GCV160 engines.
– Best for Advanced Users: Honda Genuine 98079-56846 – If you want absolute certainty and don’t mind paying a premium, the OEM plug guarantees perfect fit, finish, and performance. Great for restorations or warranty-sensitive applications.
Conclusion: Making the Right Choice
Choosing the right spark plug for your Honda GCV160 isn’t just about swapping out a worn part—it’s about ensuring your engine runs efficiently, safely, and without leaks. While a gas leak near the spark plug may point to other issues like gasket failure or carburetor problems, replacing the spark plug with a high-quality, correctly specified unit is a critical step in diagnosing and resolving the problem. By focusing on thread size, heat range, gap, sealing integrity, and brand reputation, you’ll avoid common pitfalls and extend the life of your equipment.
Remember, the cheapest option isn’t always the best value, and the most expensive plug isn’t necessary for every user. Assess your usage patterns, budget, and maintenance goals. Whether you’re a casual weekend mower or a commercial landscaper, there’s a spark plug that fits your needs perfectly. Use the guidance in this article to make an informed, confident decision—and don’t forget to address any underlying causes of fuel leakage beyond the plug itself.
Take action today: inspect your current plug, verify your engine’s specifications, and invest in a quality replacement. Your GCV160 will thank you with smoother starts, better fuel economy, and years of reliable service. And if you’ve been battling that mysterious gas leak, you might just find that the right spark plug—installed correctly—is the key to finally solving it.