If you own a Honda GCV160 engine—whether it’s powering your lawnmower, pressure washer, or generator—you know how frustrating it can be when the engine is hard to pull start. That stubborn resistance, the extra effort required just to get the engine turning over, often signals an underlying issue that many users overlook: the spark plug. While it may seem like a small, insignificant component, the spark plug plays a critical role in ignition efficiency, combustion consistency, and overall engine performance. A worn, fouled, or incorrect spark plug can directly contribute to hard starting, poor fuel economy, rough idling, and even engine stalling.
This comprehensive guide is designed to help you identify the best spark plug for your GCV160 engine, especially when you’re dealing with hard-to-pull symptoms. Whether you’re a homeowner maintaining your lawn equipment or a professional landscaper relying on consistent performance, choosing the right spark plug can make all the difference. In this article, you’ll learn not only which spark plugs are top performers for the GCV160, but also how to evaluate key factors like heat range, electrode design, material composition, and compatibility. We’ll walk you through common mistakes, budget considerations, expert tips, and real-world testing insights so you can make an informed decision—no guesswork required.
The market is flooded with spark plug options, from generic aftermarket brands to OEM (Original Equipment Manufacturer) parts and premium performance variants. While it might be tempting to grab the cheapest option or assume all spark plugs are interchangeable, the reality is that even small differences in design and materials can have a big impact on how your engine starts and runs. This guide cuts through the noise, offering expert-level analysis based on technical specifications, user feedback, and hands-on testing. By the end, you’ll know exactly what to look for, what to avoid, and which spark plug will deliver reliable, easy starts every time you pull the cord.
What to Look for When Buying Buying Guide
1. Heat Range Compatibility
The heat range of a spark plug determines how well it can dissipate heat from the combustion chamber. For the Honda GCV160, which operates under moderate to high load conditions in applications like mowing thick grass or running a pressure washer, selecting a spark plug with the correct heat range is essential. A plug that runs too hot can cause pre-ignition or detonation, while one that runs too cool may foul quickly due to incomplete combustion. The GCV160 typically uses a medium heat range plug—often labeled as “5” or “6” in some numbering systems—so it’s crucial to match this specification. Using a plug with an incorrect heat range is one of the leading causes of hard starting, especially in engines that have been running for extended periods.
When evaluating heat range, look for manufacturer specifications that align with Honda’s recommendations. OEM plugs like the Honda 98079-55846 or equivalents from reputable brands such as NGK or Denso are engineered to match the GCV160’s thermal requirements. Avoid universal or “fits-all” spark plugs that don’t specify heat range, as they may not perform optimally under real-world conditions.
2. Electrode Material and Design
The material and design of the spark plug’s electrodes directly influence spark strength, durability, and resistance to fouling. Traditional copper-core plugs are common and affordable, but they tend to wear out faster and may struggle with consistent spark delivery in high-compression or high-RPM applications. For the GCV160, which operates at relatively high speeds during normal use, a plug with a nickel-alloy or platinum-tipped electrode offers better longevity and more reliable ignition.
Platinum plugs, such as the NGK CR6HSA-P, feature a fine-wire center electrode that enhances spark efficiency while reducing voltage requirements. This means the ignition coil doesn’t have to work as hard, which can be especially beneficial in older engines where coil performance may be declining. Iridium plugs, while more expensive, offer even greater durability and finer electrode tips, resulting in a stronger, more focused spark. However, for most GCV160 applications, a high-quality platinum or nickel-alloy plug strikes the ideal balance between performance and cost.
3. Gap Specification
The spark plug gap—the distance between the center and ground electrodes—is a critical factor that affects ignition timing and spark intensity. The Honda GCV160 requires a specific gap, typically around 0.024 to 0.028 inches (0.6 to 0.7 mm), though this can vary slightly depending on the model year and application. A gap that’s too wide can prevent the spark from jumping reliably, especially if the ignition coil is weak, while a gap that’s too narrow may produce a weak spark that fails to ignite the air-fuel mixture efficiently.
Always check the gap before installation, even if the plug is labeled as “pre-gapped.” Manufacturing tolerances and shipping can alter the gap slightly. Use a quality gap tool to measure and adjust as needed. Never pry the ground electrode with a screwdriver, as this can damage the plug or create an uneven gap. A properly gapped plug ensures consistent combustion, reduces misfires, and makes starting easier—especially important when dealing with hard-to-pull engines.
4. OEM vs. Aftermarket Compatibility
Honda recommends specific spark plugs for the GCV160, such as the 98079-55846 (NGK CR6HSA) or 98079-56846 (Denso W16EX-U). These OEM-spec plugs are engineered to meet exact performance, heat range, and dimensional requirements. While aftermarket equivalents from brands like Autolite, Champion, or Bosch may claim compatibility, subtle differences in electrode design, thread length, or insulator shape can lead to poor performance or even engine damage.
For example, a plug with a shorter reach (thread length) might not seat properly, leading to compression leaks or overheating. Conversely, a plug with a longer reach could protrude into the combustion chamber and cause piston damage. Always verify thread size (usually 14mm), reach (typically 12.7mm), and hex size (16mm) against your engine’s specifications. When in doubt, stick with OEM or direct equivalents from trusted manufacturers.
5. Resistance to Fouling and Deposits
Carbon fouling—black, sooty deposits on the electrode—is a common issue in small engines like the GCV160, especially when using ethanol-blended fuels or running the engine rich. A fouled spark plug won’t produce a strong spark, leading to hard starting, misfires, and poor acceleration. Look for spark plugs with features that resist fouling, such as a projected nose design, which positions the electrode further into the combustion chamber for better exposure to the flame front.
Platinum and iridium plugs generally resist fouling better than standard copper plugs due to their superior heat tolerance and cleaner burn characteristics. Additionally, some plugs feature a tapered cut ground electrode or a V-groove center electrode, which improves flame kernel development and reduces the chance of deposit buildup. If your engine frequently experiences hard starts after short runs or in humid conditions, consider upgrading to a fouling-resistant plug.
6. Ease of Installation and Removal
While it may seem minor, the ease of installing and removing a spark plug can impact long-term maintenance. A plug that’s difficult to access or prone to seizing can turn a simple tune-up into a frustrating ordeal. The GCV160’s compact design means the spark plug is often tucked under a shroud or near other components, so using a plug with a standard 16mm hex size and a well-designed insulator tip can make a big difference.
Consider using a spark plug socket with a rubber insert to securely grip the plug during installation and removal. Anti-seize compound is generally not recommended for aluminum cylinder heads, as it can lead to over-torquing and thread damage. Instead, ensure the threads are clean and apply a small amount of dielectric grease to the boot to prevent moisture intrusion and make future removal easier.
7. Brand Reputation and Quality Control
Not all spark plugs are created equal, even if they look similar. Reputable brands like NGK, Denso, Bosch, and Champion invest heavily in quality control, materials science, and testing to ensure consistent performance. Generic or off-brand plugs may save you a few dollars upfront, but they often suffer from inconsistent gaps, poor electrode alignment, or substandard materials that lead to premature failure.
Look for brands with a proven track record in small engine applications. NGK, for example, is the OEM supplier for many Honda engines and is known for its precision manufacturing. Denso offers excellent heat range accuracy and durability, while Bosch provides reliable performance at a competitive price. Reading user reviews and checking for certifications (such as ISO 9001) can also help you identify trustworthy manufacturers.
8. Warranty and Support
While spark plugs are consumable items, some manufacturers offer limited warranties or satisfaction guarantees, especially on premium models. This can be a sign of confidence in their product’s quality and performance. Additionally, reputable brands often provide detailed technical support, compatibility charts, and troubleshooting guides—valuable resources when diagnosing hard-start issues.
Check the packaging or manufacturer website for warranty information. Some retailers also offer return policies for unopened or unused spark plugs, giving you peace of mind if you accidentally purchase the wrong type. While warranty shouldn’t be the primary deciding factor, it can tip the scales when comparing otherwise similar options.
Different Types of Buying Guide
Common Buying Mistakes to Avoid
❌ Mistake: Ignoring the Manufacturer’s Specifications
Why it’s bad: Using a spark plug that doesn’t match Honda’s recommended specifications—such as thread size, reach, or heat range—can lead to poor performance, hard starting, or even engine damage. For example, a plug with the wrong reach might not seal properly or could interfere with the piston.
What to do instead: Always consult your owner’s manual or a trusted parts diagram to confirm the correct spark plug model. Stick with OEM numbers like 98079-55846 or verified equivalents.
❌ Mistake: Choosing Based Solely on Price
Why it’s bad: The cheapest spark plug may save you a few dollars, but it could fail prematurely, foul quickly, or cause inconsistent ignition—leading to more frequent replacements and frustrating hard starts.
What to do instead: Invest in a quality plug from a reputable brand. A $10 platinum plug that lasts two seasons is better value than a $4 copper plug that fails after one.
❌ Mistake: Overlooking the Spark Plug Gap
Why it’s bad: A misgapped plug can cause weak sparks, misfires, or failure to start. Even pre-gapped plugs can shift during shipping or handling.
What to do instead: Always measure the gap with a proper tool before installation. Adjust gently using a gap gauge—never force the electrode.
❌ Mistake: Using Anti-Seize on Aluminum Heads
Why it’s bad: Anti-seize can increase torque readings, leading to over-tightening and thread damage in aluminum cylinder heads. It can also conduct electricity and interfere with grounding.
What to do instead: Install the plug dry or with a small amount of dielectric grease on the boot. Torque to manufacturer specs (typically 13-18 ft-lbs for small engines).
❌ Mistake: Reusing Old Spark Plugs
Why it’s bad: Even if an old plug looks clean, internal wear, electrode erosion, or micro-cracks can reduce performance. Reusing it may not solve hard-start issues.
What to do instead: Replace the spark plug annually or every 100 hours of operation, whichever comes first. Keep a spare on hand for emergencies.
❌ Mistake: Buying Generic “Universal Fit” Plugs
Why it’s bad: Universal plugs often compromise on heat range, electrode design, or materials. They may fit physically but perform poorly under load.
What to do instead: Choose a plug specifically designed for small engines or listed as a direct replacement for the GCV160.
❌ Mistake: Neglecting Other Hard-Start Causes
Why it’s bad: While a bad spark plug is a common cause of hard starting, it’s not the only one. Ignoring fuel system issues, air filter clogs, or carburetor problems can lead to repeated plug replacements without solving the root issue.
What to do instead: Perform a full tune-up: check the air filter, fuel quality, carburetor, and compression. Replace the spark plug as part of a comprehensive maintenance routine.
Budget Guidelines: How Much Should You Spend?
Entry-Level ($3 – $6): This range includes basic copper-core spark plugs from brands like Autolite or Champion. These are fine for occasional use or as temporary replacements, but they wear out faster and may struggle with consistent ignition in demanding conditions. Expect to replace them every season or sooner if the engine is hard to start.
Mid-Range ($6 – $12): This is the sweet spot for most GCV160 owners. Platinum-tipped plugs from NGK, Denso, or Bosch offer excellent durability, reliable spark, and resistance to fouling. They’re ideal for regular use and provide the best balance of performance and cost. Many users report easier starts and smoother operation after upgrading to this tier.
Premium ($12 – $18): Iridium-enhanced plugs represent the top tier for performance and longevity. With ultra-fine electrode tips and superior heat tolerance, they deliver the strongest, most consistent spark. While overkill for light-duty mowing, they’re worth considering for professionals or those operating in harsh conditions. These plugs can last multiple seasons with proper maintenance.
Luxury ($18+): At this price point, you’re likely looking at specialty or racing-grade plugs with advanced features like multiple ground electrodes or laser-welded tips. These are unnecessary for the GCV160 and offer diminishing returns. Stick with premium iridium unless you’re modifying the engine for high-performance applications.
Expert Tips for Getting the Best Deal
1. Buy During Off-Season Sales: Retailers often discount small engine parts in late fall or early winter, after the mowing season ends. Stock up during these sales to save 20-30% on quality plugs.
2. Purchase from Authorized Dealers: Buy from Honda dealers, reputable online retailers (like Amazon, eBay, or PartsTree), or local hardware stores with good return policies. Avoid unknown sellers offering “too good to be true” prices.
3. Check for Multi-Packs: Some brands offer value packs of 2-4 plugs at a discounted rate. Even if you only need one now, having spares ensures you’re never stranded with a fouled plug.
4. Read Recent User Reviews: Look for reviews from users with the same engine model (GCV160) and application (e.g., lawnmower, pressure washer). Real-world feedback is more reliable than marketing claims.
5. Verify Compatibility Before Buying: Use online compatibility tools or cross-reference part numbers. For example, NGK CR6HSA is equivalent to Honda 98079-55846—confirm this before purchasing.
6. Consider the Total Cost of Ownership: A cheaper plug may cost less upfront but require more frequent replacement. Factor in labor time and downtime when evaluating value.
7. Test the Old Plug Before Replacing: Remove the old plug and inspect it. If it’s wet with fuel, the issue may be a rich mixture or flooded engine—not the plug itself. Address the root cause to avoid repeating the problem.
8. Keep Records of Maintenance: Note the date and hours of operation when you replace the plug. This helps you track performance and schedule future replacements proactively.
Frequently Asked Questions
Q: Can a bad spark plug really cause hard starting on a GCV160?
A: Absolutely. A worn, fouled, or incorrect spark plug can fail to produce a strong enough spark to ignite the air-fuel mixture, especially when the engine is cold or under load. This results in weak or inconsistent combustion, making the engine harder to pull start.
Q: How often should I replace the spark plug in my GCV160?
A: Honda recommends replacing the spark plug annually or every 100 hours of operation, whichever comes first. If you notice hard starting, rough idling, or reduced power, inspect the plug sooner.
Q: Is it safe to use a different brand spark plug as long as the part number matches?
A: Yes, as long as the replacement is a direct equivalent (same thread size, reach, heat range, and gap). NGK, Denso, and Bosch all make high-quality replacements for Honda OEM plugs.
Q: Should I gap the spark plug before installing it?
A: Yes. Even if the plug is labeled as pre-gapped, always verify the gap with a proper tool. The correct gap for most GCV160 engines is 0.024–0.028 inches.
Q: Can I clean and reuse a fouled spark plug?
A: You can clean a mildly fouled plug with a wire brush or spark plug cleaner, but it’s not recommended for long-term reliability. Internal wear and electrode erosion can’t be seen, so replacement is the safest option.
Q: What’s the difference between platinum and iridium spark plugs?
A: Iridium has a higher melting point and greater hardness than platinum, allowing for finer electrode tips and longer life. However, for the GCV160, platinum offers nearly identical performance at a lower cost.
Q: Will a hotter or colder spark plug fix hard starting?
A: Not necessarily. Using a plug with the wrong heat range can make the problem worse. Stick with the manufacturer’s recommended heat range unless a mechanic advises otherwise based on engine modifications.
Q: Can I use a spark plug from a different small engine?
A: Only if it matches the exact specifications (14mm thread, 12.7mm reach, correct heat range). Even small differences can affect performance or cause damage.
Q: Does ethanol fuel affect spark plug life?
A: Yes. Ethanol can cause carbon buildup and reduce lubrication, leading to faster fouling. Use fresh, ethanol-free fuel when possible and replace the plug more frequently if using E10.
Q: How do I know if the spark plug is the real cause of hard starting?
A: Perform a spark test: remove the plug, reconnect it to the wire, ground it against the engine, and pull the starter. A strong blue spark indicates the plug and ignition system are working. No spark or a weak orange spark suggests a problem.
Our Final Recommendations
Best for Budget-Conscious Buyers: NGK CR6HSA (Copper) – At around $5, this is the OEM-spec copper plug that delivers reliable performance for light-duty use. It’s a great choice if you’re on a tight budget and maintain your equipment regularly.
Best Overall Value: NGK CR6HSA-P (Platinum) – For just a few dollars more, this platinum-tipped version offers longer life, better fouling resistance, and more consistent ignition. It’s the sweet spot for most GCV160 owners.
Best Premium Option: Denso IW16 (Iridium) – With a fine-wire iridium center electrode, this plug provides the strongest spark and longest lifespan. Ideal for professionals or those who want maximum reliability.
Best for Beginners: Champion RJ19LM (Copper) – Easy to find and install, this plug is a solid entry-level option. Just remember to check the gap and replace it annually.
Best for Advanced Users: Bosch WR7DC+ (Platinum) – Offers excellent heat dissipation and a durable design. Great for users who perform their own maintenance and want a plug that can handle variable conditions.
Conclusion: Making the Right Choice
Choosing the right spark plug for your Honda GCV160 isn’t just about fixing a hard-to-pull engine—it’s about ensuring reliable performance, extending engine life, and minimizing downtime. As we’ve explored, the spark plug is a small but mighty component that directly affects ignition efficiency, combustion quality, and overall engine behavior. By focusing on key factors like heat range, electrode material, gap specification, and brand reputation, you can make a confident, informed decision that delivers real-world results.
Remember, the cheapest option isn’t always the best value, and compatibility matters more than convenience. Whether you opt for an OEM-spec copper plug or upgrade to a premium iridium model, the goal is the same: a strong, consistent spark that makes starting effortless. Combine your new spark plug with regular maintenance—clean air filters, fresh fuel, and proper storage—and your GCV160 will reward you with years of dependable service.
Don’t let a stubborn pull cord keep you from enjoying your outdoor tasks. Take the time to select the right spark plug, install it correctly, and maintain it properly. Your engine—and your arms—will thank you. Now that you’re armed with expert knowledge, it’s time to take action. Replace that old plug, feel the difference, and get back to work with confidence.