Aftermarket Spark Plug Guide for the 2014-2021 Harley Tri Glide Ultra
Keep your Tri Glide's V-twin engine firing on all cylinders with the right set of new spark plugs.
- Symptoms of bad plugs include rough idle, misfires, hard starts, and poor fuel economy.
- Both Champion and NGK are trusted aftermarket brands; Champion is often the OEM supplier, while NGK offers popular iridium upgrades.
- Always verify the spark plug gap before installation; the spec is different for Twin Cam (2014-2016) and Milwaukee-Eight (2017-2021) engines.
- Replacement is a simple DIY task that can be done in under 30 minutes with basic tools.
Signs of Failing Spark Plugs
Worn or fouled spark plugs can cause a range of noticeable problems on your Tri Glide. You're not just losing performance; you could be risking damage to other engine components. Look out for these common symptoms:
- Rough Idling: The engine may shake or vibrate more than usual when stopped.
- Hard Starts: The engine takes longer to turn over or struggles to start, especially when cold.
- Engine Misfires: You might feel a hesitation or stumble during acceleration as a cylinder fails to fire correctly.
- Reduced Fuel Economy: Inefficient combustion means you'll be stopping for gas more often.
- Loss of Power: Your Trike may feel sluggish and less responsive to the throttle.
Don't Ignore Misfires
A persistent misfire can allow unburnt fuel to enter the exhaust system, potentially damaging the catalytic converter. If your check engine light is flashing, it's a sign of a serious misfire that needs immediate attention.
Choosing the Right Aftermarket Spark Plugs
When it comes to aftermarket spark plugs for your 2014-2021 Tri Glide Ultra, you have reliable options that meet or exceed OEM quality. Harley-Davidson's stock plugs are often made by Champion, so choosing an aftermarket Champion plug is a safe bet for OEM-equivalent performance. NGK is another top-tier brand widely trusted by Harley owners. Many riders find NGK plugs, especially their iridium models, offer long life and excellent performance.
Here’s a breakdown of your choices:
- Standard Copper (Good): Brands like Champion offer copper plugs that are very similar to the original factory plugs. They are affordable and provide reliable performance but have the shortest lifespan. They are a great choice if you stick to a regular maintenance schedule.
- Iridium (Better/Best): Brands like NGK offer iridium plugs, which are a significant upgrade. They have a fine-wire center electrode that requires less voltage to fire, which can improve starting and throttle response. Iridium plugs last much longer than copper plugs, making them a good value over time.
Always Check the Gap
Even if a spark plug is advertised as "pre-gapped," it's crucial to check the gap with a feeler gauge before installation. The correct gap ensures the most efficient spark. For 2014-2016 Twin Cam models, the gap is typically 0.038"-0.043". For 2017-2021 Milwaukee-Eight models, the gap is tighter, around 0.031"-0.035". Always confirm the spec in your owner's manual.
🎬 Watch how to properly gap and install your new plugs.Cost of New Aftermarket Spark Plugs
Replacing spark plugs is one of the more affordable maintenance tasks. Aftermarket plugs offer significant savings without sacrificing quality.
| Item | Price Range |
|---|---|
| New Aftermarket Spark Plugs (per plug) | $3.91 - $14.32 |
| New OEM Harley-Davidson Spark Plugs (per plug) | $7.00 - $12.00 |
| Shop Labor for Installation | $45 - $150 |
Frequently Asked Questions (FAQ)
How often should I replace the spark plugs on my Tri Glide?
Harley-Davidson typically recommends replacing spark plugs every 30,000 miles or every two years, whichever comes first. However, many owners replace them more frequently, such as with every other oil change, to maintain peak performance. Using long-life iridium plugs may extend this interval.
Is it difficult to replace the spark plugs myself?
No, this is a very straightforward job for a DIY mechanic. Access to the plugs on the Tri Glide's V-twin engine is excellent. You will need a 5/8" spark plug socket, a ratchet, and a torque wrench. The entire job can usually be completed in under 30 minutes.
🎬 See a step-by-step spark plug change on a Twin Cam Trike.Are expensive spark plugs worth it for my Harley?
For most riders with stock or lightly modified engines, standard copper plugs from Champion or NGK are perfectly fine. Upgrading to iridium plugs from NGK can provide benefits like longer service life, easier starting, and a smoother idle, which many riders feel is worth the extra cost.
Do I need to put anti-seize on the new spark plug threads?
This is a topic of debate. Some mechanics apply a very light coating of anti-seize to prevent the plugs from getting stuck in the aluminum cylinder heads. However, some plug manufacturers, including NGK, advise against it as their plugs have special plating to prevent seizing. The official Harley service manual often specifies installing plugs dry and clean. If you do use anti-seize, be sure to reduce the torque setting by about 10-15% to avoid over-tightening.
What are the OEM part numbers for my Tri Glide's spark plugs?
For the Twin Cam engines (2014-2016), the standard Harley-Davidson plug is part number 32362-04A, also known as the 6R12. For the Milwaukee-Eight engines (2017-2021), the OEM part number is 31600012. Aftermarket brands like Champion and NGK provide direct cross-references to these numbers.
Helpful Videos
Technical Specifications
OEM Part Numbers: 32362-04A 6R12 31600012
Engine Type: Twin-Cooled Twin Cam 103 (2014-2016), Twin-Cooled Milwaukee-Eight 114 (2017-2021). Spark Plug Socket Size: 5/8". Torque Spec: 12-18 ft-lbs. Twin Cam Gap: 0.038"-0.043". Milwaukee-Eight Gap: 0.031"-0.035".
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Harley Davidson FLHTCUTG Tri Glide Ultra: