Harley-Davidson has introduced a new Stage IV Big Bore kit that promises to transform the performance of its V2 engines from 1,923 cc to an impressive 2,153 cc, all without needing to remove the motorcycle’s engine.
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With this upgrade, rear-wheel horsepower can exceed 131 hp, making it one of the most radical performance enhancements offered directly by the American brand.
More Displacement, More Power
Designed for Touring models with 117 cubic inch engines from the 2024 model year onward — including the new Road Glide and Street Glide with enhanced cylinder head cooling — the kit delivers a significant boost:
- Torque increases from 175 Nm to 189 Nm
- Horsepower rises from 108 hp to 131 hp
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Harley-Davidson is focusing not just on higher revs but on a classic sporty tuning approach, based on a greater air-fuel mixture in the combustion chamber and optimized gas exchange.
Engineering for Maximum Performance
The new kit includes:
- Cylinders with a 109.5 mm diameter (previously 103.5 mm)
- New pistons
- Sport camshaft
- Revised injection system
- New aluminum intake manifold
- Machined cylinder heads with more efficient flow channels
- New injectors with a 6.8 g/s flow capacity
The crankshaft and the 114.3 mm stroke remain unchanged. This setup forms the basis of the engine that powers the CVO Road Glide RR, currently Harley’s most powerful production motorcycle, priced at $110,000.
Cost of the Upgrade
In the United States, the 131 kit is offered for around $4,000, while in Europe, similar packages cost approximately €5,000. Additional expenses include installation, electronic tuning, and potential homologation processes — especially in Europe, where the registered version delivers around 125 hp and just over 180 Nm at the rear wheel.
An Upgrade for Those Seeking Extreme Power
The aim of the new Big Bore kit is clear: to deliver maximum performance without compromising the legendary robustness of Harley-Davidson engines. For enthusiasts eager to get the most out of their Touring models, this investment promises a radical transformation both in performance and riding sensation.
Source and images: Harley-Davidson. This content was created with the help of AI and reviewed by the editorial team.
