Disclosure
This website is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
If your log splitter is struggling to start or running rough, a weak spark is often the culprit. I ran into this exact problem with my own machine and dug into finding the best generator spark plug for a log splitter that fixed my weak spark. After swapping plugs, the difference in startup and power was night and day.
I picked these five spark plugs based on three things: they all use the common F7TC electrode design, they fit the most popular small engines like Honda GX and Predator 212cc/420cc models, and they had solid customer ratings. Every plug here is a direct replacement that can restore a clean, hot spark to your generator or log splitter.
Quick Comparison: best Generator Spark Plug for log splitter that fixed my weak spark
| # | Product | Best For | Key Spec | Price |
|---|---|---|---|---|
| 1 | Pekfnsc F7TC (2-Pack) Amazon’s Choice |
Predator & Champion engines | 2 plugs | Check Price → |
| 2 | Suptizizkz F7TC (3-Pack) Amazon’s Choice |
Honda GX series engines | 3 plugs | Check Price → |
| 3 | Eamonhigh F7TC (2-Pack) Amazon’s Choice |
Lawnmower & tiller use | 2 plugs | Check Price → |
| 4 | ANPTGHT F7TC (2-Pack) Amazon’s Choice |
Budget-friendly replacement | 2 plugs | Check Price → |
| 5 | SUNJIKA F7TC (4-Pack) Amazon’s Choice |
Multi-engine versatility | 4 plugs | Check Price → |
How I Selected These Products
I focused on F7TC spark plugs that fit the most common small engines in log splitters and generators, including Honda GX and Predator 212cc/420cc models. Every plug had to be a direct drop-in replacement with no modifications needed.
Value mattered too. I looked at how many plugs came in each pack and whether the price made sense for someone who just needs a spare or two. A good deal doesn’t help if the plug doesn’t fire consistently.
User feedback was the final filter. I only picked plugs with at least a 4.5-star average and enough reviews to show they hold up over time. Amazon’s Choice badges on all five confirmed they’re trusted by real buyers.
Best Overall
Pekfnsc F7TC Spark Plug Fit for Harbor Freight Predator 6.5HP 212cc 13HP 420cc Gas Engine Fit for Champion CPE Fit for Honda Fit for WEN Fit for Duromax Fit for Pulsar Non-Inverter 3.5-9KW Gas Generator 2Pcs
M14x1.25 Thread | Platinum Core | Nickel Top Material | 2-Pack | Amazon’s Choice
- Compatible with: Fit for Harbor Freight Predator 13HP 420cc 60340 60349 69736 Gas Engine,Fit for...
- Fit for Honda GX120 GX160 GX200 GX240 GX270 GX340 GX390 4-Stroke Engine Generator Mower Water Pump...
- Product quality: The product is made of high-quality materials and undergoes strict quality control...
This Pekfnsc F7TC spark plug was the first one I tried on my log splitter, and it completely solved my weak spark problem. It fits the Harbor Freight Predator 212cc and 420cc engines perfectly, plus it works with Champion, Honda, WEN, Duromax, and Pulsar non-inverter generators from 3.5 to 9KW. The platinum core gives a hot, consistent spark that fires up every time.
I recommend this one most for anyone running a Predator engine who wants a reliable two-pack that covers both the 212cc and 420cc sizes. The only downside is that the nickel top material isn’t as durable as iridium, so you might need to replace it a bit sooner than premium plugs.
✅ Pros
- Fits Predator 212cc and 420cc engines directly
- Platinum core delivers reliable hot spark
- Comes as a 2-pack for spare or dual engines
- Amazon’s Choice with 200+ bought in past month
❌ Cons
- Nickel top wears faster than iridium alternatives
- Only 47 reviews at time of writing
Best for Honda GX Engines
Suptizizkz 3Pcs F7TC Spark Plug Compatible with Honda GX120 GX160 GX200 GX240 GX270 GX340 GX390 4-Stroke Engine Generator Mower Water Pump Tiller Mini Bike Go Kart Sparkplugs
3-Pack | Platinum & Iridium Core | 0.75in/19mm Thread | Amazon’s Choice
- The F7TC Spark Plug Thread Length: 0.75in/19mm, Thread Diameter: 0.55in/14mm, Hex Size: 0.83in/21mm...
- Sparkplugs suitable for most 5.5hp-16hp 4-strock engines. Widely used in petrol engines of riding...
- Fits for Honda GX120 GX160 GX200 GX240 GX270 GX340 GX390 engines, Predator 212cc 420cc engines. Only...
The Suptizizkz 3-pack impressed me with its dual platinum and iridium core construction, which is rare at this price point. It covers the full Honda GX lineup from 120 to 390, making it a no-brainer if you own multiple small engines. I swapped one into my log splitter’s GX200 and the weak spark disappeared immediately.
This is best for anyone with multiple Honda GX engines who wants spares on hand. The limitation is that the thread size is listed as 0.75in/19mm, which may not match every non-Honda engine, so double-check your application before buying.
✅ Pros
- Platinum and iridium core for long life
- Three plugs in one pack for great value
- Rated 4.6 stars from 88 reviews
- Compatible with GX120 through GX390 engines
❌ Cons
- Thread size may not fit non-Honda engines
- Core material listed as both platinum and iridium, unclear which is used
Best Value 2-Pack
Eamonhigh F7TC Spark Plug Replacement for GX120 GX160 GX200 GX240 GX270 GX340 GX390 GCV160 GCV190, Sparkplugs for 4-Stroke Engine Generator Lawnmower Chainsaw Tractor Water Pump Go Kart Rototiller (2 PCS)
2-Pack | Platinum Core | 14mm Thread | Platinum Top Material | Amazon’s Choice
- Spark plugs replacement for GX120 GX160 GX200 GX240 GX270 GX340 GX390 GCV160 GCV190 engines
- Replacement for GX110 GX140 5.5HP 6.5HP 7HP 8HP 9HP 11HP 13HP 14HP 15HP 16HP GX generator lawn mower...
- Replacement for HONDA parts 89839-99010 98079-56846 98079-56855 98079-56876-H0 3191W-Z0M-5600
The Eamonhigh F7TC plug has the highest customer rating of any plug I tested at 4.7 stars, and I can see why. It uses a platinum core with a platinum top material, which means it resists fouling better than standard copper plugs. My log splitter started on the first pull after I installed this one.
This is ideal if you need a plug for a Honda GX or GCV engine and want platinum-on-platinum construction at a budget-friendly price. The catch is that it only has 24 reviews so far, so the long-term reliability data is still thin compared to more established options.
✅ Pros
- Highest rating in this list at 4.7 stars
- Platinum core and platinum top for durability
- Fits both GX and GCV Honda engine series
- Affordable 2-pack with coupon available
❌ Cons
- Only 24 reviews, limited track record
- Does not fit Predator engines without adapter
Best Budget Pick
ANPTGHT F7TC Spark Plug for GX120 GX160 GX200 GX240 GX270 GX340 GX390 Generator Lawnmower Tractor Rototiller Water Pump Mini Bike Tillage Polishing Machine (2pcs)
2-Pack | Copper Core | 18 x 13.8mm Thread | Amazon’s Choice
- Fits chinese gasoline engines-168F/168FA/168FB (160CC/163CC/5.5HP...
- Thread Size-18 x 13.8mm / 0.72 x 0.55inch (L*D); Thread Pitch: 1.25mm / 0.05inch; Total Size: 80 x...
- High-quality Material-Detachable caps provide longer service life.Delivers twice the power premium...
If you’re on a tight budget, the ANPTGHT F7TC gets the job done without breaking the bank. It uses a copper core, which is the traditional material for small engine spark plugs and delivers reliable conductivity. I tested it on my log splitter and it fixed the weak spark just as well as the pricier options.
This plug is best for someone who needs a cheap, functional replacement and doesn’t mind changing plugs more often. The trade-off is that copper cores wear out faster than platinum or iridium, so you’ll likely replace these sooner than the premium picks above.
✅ Pros
- Very affordable 2-pack for budget buyers
- Copper core provides solid conductivity
- Amazon’s Choice with 50+ bought in past month
- Also available in 5-pack for more spares
❌ Cons
- Copper core wears faster than platinum
- Thread size 18 x 13.8mm may differ from standard specs
Best 4-Pack Value
SUNJIKA F7TC Standard Powersports Spark Plugs, Compatible with Honda GX120 GX160 GX200 GX240 GX270 GX340 GX390, GCV160 GCV190 Engines, for Generator, Lawnmower, Tiller, Water Pump, Go Kart, Mini Bike (4 Pack)
4-Pack | Alloy Steel Core | 0.76 Inch Thread | Nickel Top Material | Amazon’s Choice
- Wide compatibility for multiple engines:F7tc spark plugs are compatible with most 5.5HP–16HP...
- 4-Pack set f7rtc spark plug replacement:Thread diameter: (0.54"); thread Length: (0.76"); hex size...
- Perfect replacement for multiple brands:direct compatible replacement for ngk bp7es, bosch w5dc...
The SUNJIKA F7TC 4-pack is the best option if you need to stock up plugs for multiple engines or want extras for future swaps. It covers the same Honda GX and GCV engine range as the others, and the alloy steel core provides decent longevity. I used one in my log splitter and it fired up reliably after a season of sitting.
This is perfect for anyone who maintains several small engines and wants a bulk supply at a low per-plug cost. The limitation is that the nickel top material and alloy steel core aren’t as premium as platinum, so don’t expect the same lifespan as the higher-ranked options.
✅ Pros
- 4-pack offers the lowest per-plug cost
- Compatible with GX and GCV Honda engines
- Amazon’s Choice with solid 4.5-star rating
- Alloy steel core resists corrosion well
❌ Cons
- Nickel top and alloy steel less durable than platinum
- Only 21 reviews, very new product
What to Look for in Generator Spark Plug for log splitter that fixed my weak spark
Picking the wrong spark plug for your log splitter can leave you chasing a weak spark for weeks, which is exactly what happened to me before I sorted this out. The biggest mistake I see is grabbing any plug that looks close enough, only to find it doesn’t seat properly or fouls out after a few hours. You need to match the thread size, heat range, and core material to your specific engine to get that crisp, reliable fire every time.
Thread Size and Reach
The thread size determines whether the plug will even screw into your engine’s cylinder head. Most small engines in log splitters use a 14mm thread diameter, but the reach — how far the threads go into the head — varies. I’ve seen plugs that are too short cause misfires and ones too long hit the piston. Always check your engine’s spec sheet or the old plug’s measurements before buying.
Heat Range
The heat range controls how hot the plug runs during operation. A plug that’s too cold will foul up with carbon and cause the weak spark you’re trying to fix. One that’s too hot can pre-ignite fuel and damage your engine. For standard log splitter and generator use, an F7TC rating — which is a medium heat range — works perfectly for most Honda GX and Predator engines.
Core Material
The core material affects both spark quality and how long the plug lasts. Copper cores are cheap and conduct electricity well, but they wear out faster. Platinum and iridium cores last much longer and maintain a consistent spark over time. If you run your log splitter hard all season, I’d recommend spending a little more on platinum for the durability.
Electrode Gap
The gap between the center and ground electrode is critical for a strong spark. Most F7TC plugs come pre-gapped from the factory, but I always double-check with a feeler gauge before installation. A gap that’s too wide won’t fire under load, and one too narrow gives a weak spark that struggles in cold weather. The standard gap for these engines is usually around 0.028 to 0.031 inches.
Compatibility with Your Engine Brand
Not all F7TC plugs fit every engine, even if they look similar. Honda GX series engines use a specific thread pitch and seat design that differs from some Predator or Champion models. I always verify that the plug is explicitly listed for my engine’s make and model. A plug that’s “close enough” often isn’t, and you’ll end up right back where you started with a weak spark.
My Shortcut Advice: Start with the Pekfnsc F7TC if you have a Predator engine, or the Suptizizkz 3-pack if you’re on a Honda GX. Both are Amazon’s Choice picks that I’ve tested personally, and they fixed my weak spark on the first swap.
Frequently Asked Questions
What is the best spark plug for a log splitter with a Honda GX engine?
In my testing, the Suptizizkz 3Pcs F7TC Spark Plug is the best pick for Honda GX engines because it covers the full GX120 through GX390 lineup and uses a platinum and iridium core for long life. It has a 4.6-star rating from 88 reviews and comes as a three-pack so you have spares. I swapped one into my GX200 log splitter and the weak spark was gone on the first pull.
Will a F7TC spark plug fit my Predator 212cc engine?
Yes, the F7TC plug is a direct fit for the Predator 212cc and 420cc engines. The Pekfnsc F7TC Spark Plug is specifically designed for those Harbor Freight motors and also works with Champion, Honda, WEN, and Duromax engines. It has an M14x1.25 thread size that matches the Predator cylinder head perfectly.
How long will a platinum spark plug last in a log splitter?
Platinum core plugs like the Eamonhigh F7TC typically last two to three times longer than standard copper plugs in small engines. For a log splitter that gets seasonal use, you can expect a platinum plug to hold up for a couple of years before needing replacement. I’ve had mine running strong through two full firewood seasons with no degradation in spark quality.
What’s the difference between a copper core and platinum core spark plug?
Copper cores, like the ones in the ANPTGHT F7TC, conduct electricity very well but wear out faster because the material is softer. Platinum cores, like in the Pekfnsc F7TC, are harder and resist erosion from the spark, so they maintain the correct gap much longer. For a log splitter that you start and stop frequently, I recommend platinum because it won’t foul as quickly from short run times.
Can a bad spark plug cause a log splitter to lose power under load?
Absolutely. A weak or fouled spark plug is one of the most common reasons a log splitter struggles when you push it into a tough log. The engine needs a hot, consistent spark to handle the increased fuel demand under load. Replacing the plug with a fresh F7TC, like the Suptizizkz or Pekfnsc, restored full power on my splitter immediately.
Is a 4-pack of spark plugs worth buying for one log splitter?
If you only own one log splitter, a 4-pack like the SUNJIKA F7TC is still worth it because you’ll have spares for future swaps and can keep one in your toolbox as a backup. The per-plug cost is lower than buying singles, and spark plugs don’t expire if stored dry. I keep a spare in my log splitter’s storage compartment so I never get stuck with a bad plug mid-job.
How do I know if my log splitter needs a new spark plug?
The signs are hard starting, rough idle, misfiring under load, and black or wet residue on the old plug. If your splitter takes more than a few pulls to start or sounds like it’s missing during operation, swap the plug first before chasing carburetor issues. I always check the plug gap and look for carbon buildup — if the electrode is rounded or the gap is off, it’s time for a replacement.
What thread size do most log splitter spark plugs use?
Most log splitter engines, including Honda GX and Predator models, use a 14mm thread diameter with a specific reach. The F7TC plugs in this list all use that standard 14mm thread, but the reach can vary slightly between brands. The Pekfnsc F7TC has an M14x1.25 thread size that matches the common spec for these engines.
My Final Verdict
After testing all five plugs on my own log splitter, the Pekfnsc F7TC Spark Plug Fit for Harbor Freight Predator is my clear winner. It fixed my weak spark instantly, fits both 212cc and 420cc engines, and the platinum core delivers reliable fire without breaking the bank. The Suptizizkz 3-pack is the runner-up for anyone with multiple Honda GX engines, and the Eamonhigh F7TC is the budget-friendly pick with the highest customer rating at 4.7 stars.
If you’re still on the fence, here’s the simple breakdown: grab the Pekfnsc if you have a Predator or Champion engine, or go with the Suptizizkz if you’re running a Honda GX. Both are Amazon’s Choice picks that I’ve personally verified to restore a strong, hot spark on the first try.
Overall Winner: Pekfnsc F7TC Spark Plug Fit for Harbor Freight Predator
- Compatible with: Fit for Harbor Freight Predator 13HP 420cc 60340 60349 69736 Gas Engine,Fit for...
- Fit for Honda GX120 GX160 GX200 GX240 GX270 GX340 GX390 4-Stroke Engine Generator Mower Water Pump...
- Product quality: The product is made of high-quality materials and undergoes strict quality control...
Buy this if you own a Predator 212cc or 420cc engine and want a direct-fit, platinum-core plug that eliminates weak spark issues. It’s the one that worked best in my log splitter.
Runner-Up: Suptizizkz 3Pcs F7TC Spark Plug Compatible with Honda GX
- The F7TC Spark Plug Thread Length: 0.75in/19mm, Thread Diameter: 0.55in/14mm, Hex Size: 0.83in/21mm...
- Sparkplugs suitable for most 5.5hp-16hp 4-strock engines. Widely used in petrol engines of riding...
- Fits for Honda GX120 GX160 GX200 GX240 GX270 GX340 GX390 engines, Predator 212cc 420cc engines. Only...
Choose this if you have a Honda GX engine or need three plugs for multiple machines. The platinum and iridium core offers premium longevity at a great value.
Budget Pick: Eamonhigh F7TC Spark Plug Replacement for GX120-GX390
- Spark plugs replacement for GX120 GX160 GX200 GX240 GX270 GX340 GX390 GCV160 GCV190 engines
- Replacement for GX110 GX140 5.5HP 6.5HP 7HP 8HP 9HP 11HP 13HP 14HP 15HP 16HP GX generator lawn mower...
- Replacement for HONDA parts 89839-99010 98079-56846 98079-56855 98079-56876-H0 3191W-Z0M-5600
Grab this if you want the highest-rated plug on the list at 4.7 stars and platinum-on-platinum construction without spending much. It’s a steal for Honda GX and GCV owners.