The new Big Bore V2 is now out under the firm’s performance label ‘Screamin’ Eagle’. The stage IV 131ci kit boosts size and power output over current motors in the range.

The official US Harley-Davidson shop is offering the Milwaukee-Eight Stage IV kit for the company’s 114 or 117ci engines.

The boost in power doesn’t come cheap though, reckon on this costing around $3,500. The good news is that kit, which is now the most powerful two-cylinder powerplant ever from Harley-Davidson official, should fit onto models from 2017 on.

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In the kit are CNC-milled cylinder heads witha a valve cross-section enlarged by one millimetre, new-shape combustion chambers, sharper camshafts, a 64mm throttle body and new intake and exhaust manifold parts.

Harley says that if the kit is installed by an authorised dealer within 60 days of purchase the the factory warranty on the bike will be retained. Harley itseld supplies the kit parts with a one-year warranty too.

Harley claims that the kit should deliver 123hp @ 5,500rpm at the rear wheel. Torque will peak at 178Nm @ 4000rpm.

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Tony Carter

Tony has been riding motorcycles for over 35 years and he's been a motorcycle writer for over 25 of those. He's ridden almost every motorcycle you can think of at most places around the world and he's partial to some racing, too. A Taurus, Tony doesn't believe in horoscopes (but then that's exactly what a Taurus would say!) but he does believe in Mandalorians and their right to earn a living.