Choosing Between Harley M8 107 and 114 Engines

Harley-Davidson riders talk a lot about the Milwaukee-Eight engines—especially the difference between the M8 107 and M8 114.
If you’re shopping for a new bike or thinking about upgrading, these two engines will come up fast.

This guide breaks down everything that actually matters: real dyno numbers, torque curves, fuel economy, and what each engine feels like on the road. You’ll also get source links and reference images so the comparison is easy to visualise.

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🔥 At a Glance: What Separates the 107 From the 114?

Both engines belong to the Milwaukee-Eight family, meaning they share:

• A 45° V-twin design
• 8 valves (4 per cylinder)
• Single camshaft
• Air/oil (and sometimes liquid) cooling
• Smooth counter-balancing

Where they differ is in displacement.
The 114 has a bigger bore and a longer stroke, meaning it pulls harder and produces more torque.

📌 Quick Specs

Spec	M8 107	M8 114
Displacement	~1,750 cc	~1,868 cc
Bore × Stroke	3.937” × 4.375”	4.000” × 4.500”
Compression	~10.0:1	~10.5:1
Architecture	Same M8 family	Same M8 family

Sources:

• Fuel Moto’s technical guide to M8 displacement: https://university.fuelmotousa.com/article/h-d-milwaukee-8-engine-big-bore-displacement-info/
• Harley-Davidson M8 overview (Wikipedia): https://en.wikipedia.org/wiki/Harley-Davidson_Milwaukee-Eight_engine

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⚡ Horsepower & Torque: Real Dyno Differences

Let’s get straight to the numbers.

📈 Factory Crank Ratings

Output	M8 107	M8 114
Horsepower	~86–87 hp	~94–100 hp
Torque	~111 lb-ft	~119–124 lb-ft

📉 Rear-Wheel Dyno Numbers

(What you actually feel at the tire)

Output	M8 107 (rear wheel)	M8 114 (rear wheel)
Horsepower	~80–82 hp	~84–86 hp
Torque	~100–102 lb-ft	~107–110 lb-ft

In short:
The 114 gives you +5–8 hp and +7–10 lb-ft everywhere in the usable RPM band.

Sources for power data:

• Harley M8 engine dyno summary: https://en.wikipedia.org/wiki/Harley-Davidson_Milwaukee-Eight_engine
• Fuel Moto dyno comparisons: https://university.fuelmotousa.com/article/h-d-milwaukee-8-engine-big-bore-displacement-info/

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🛣️ How Each Engine Feels on the Road

🧨 M8 107 — Smooth, Strong, and Efficient

The 107 is more than enough for:

• Solo riders
• Everyday riding
• Light touring
• Good MPG in the mid-40s

It makes a ton of torque early and stays strong up to around 4,500 rpm.

💪 M8 114 — Extra Muscle You Feel Instantly

The 114 gives:

• Stronger pull in every gear
• Faster roll-ons (perfect for highway passing)
• Better performance for heavy riders, luggage, or two-up touring

The torque curve is the same shape as the 107—just shifted upward.

Rider reports + factory data say mileage is similar, often mid-40s MPG for both.

Fuel economy source:

• Harley EPA data & rider averages: https://harley-davidsonforums.com/threads/107-vs-114.379780/

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🏍️ Visual Comparison: Bikes That Use the 107 vs 114

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Common Models Featuring the 107

• Street Glide (standard)
• Electra Glide Standard
• Road King (standard)
• Some Softail trims

Common Models Featuring the 114

• Street Glide Special
• Road Glide Special
• Fat Boy 114
• Heritage Classic 114
• Breakout 114
• Most premium Softails and touring upgrades

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🔍 Which One Should YOU Choose?

Choose the M8 107 if you want:

• Lower upfront bike cost
• Better fuel efficiency
• Smooth riding around town
• A solid base engine you plan to upgrade later

Choose the M8 114 if you want:

• Instant torque
• A stronger pull with a passenger
• Easier passing at highway speeds
• A bigger, more “muscular” feel

Bottom line: Both engines are excellent.
But the 114 gives you noticeably more grunt, especially where it matters from 2,500–4,000 RPM.

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📚 Sources Linked in This Article

1. Fuel Moto M8 displacement & bore/stroke reference
   https://university.fuelmotousa.com/article/h-d-milwaukee-8-engine-big-bore-displacement-info/
2. Harley-Davidson Milwaukee-Eight technical overview
   https://en.wikipedia.org/wiki/Harley-Davidson_Milwaukee-Eight_engine
3. Forum-based dyno & rider feedback resources
   • https://www.hdforums.com
   • https://www.harley-davidsonforums.com
   • https://www.roadglide.org