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New Harley-Davidson Stage IV Kits Turn Softails into Meaner Screamin’ Eagles

By October 9, 2020General Posts

by Daniel Patrascu from

It was only at the end of August that Harley-Davidson announced the availability of “the biggest, most powerful street-compliant engine Harley-Davidson has ever created,” the crate Screamin’ Eagle 131. But since a complete engine swap might seem a bit extreme for some, here come some upgrade kits for a slightly smaller tuning job.

There are a number of them made available this week by the Milwaukee bike maker, dedicated to Softail bikes manufactured from 2018 and Touring motorcycles made from 2017.

The biggest and most extreme is the 114ci to 131ci upgrade, one that is described by the company as “the largest Harley-Davidson bolt-on engine upgrade to any Milwaukee-Eight motor.” Sporting things like CNC-ported heads with 1 mm bigger valves, high-lift SE8-517 cam, high compression pistons and a 64 mm throttle body and intake manifold, the kit gets the engine’s power all the way up to 124 hp and 135 ft-lb of torque – these levels are achieved when the upgrade kit is backed by the Screamin’ Eagle Street Cannon Mufflers.

Next up is the 107ci to 128ci upgrade, featuring, naturally, about the same changes. In this case, the output levels go to the same horsepower rating as with the larger kit, 124 hp, but torque output is somewhat lower, at 127 ft-lb of torque – Screamin’ Eagle Street Cannon Mufflers are needed here as well.

The 114ci/117ci to 122ci upgrade also brings increased power. Depending on the bike it is used on, there are up to 15 percent more horsepower and 13 percent more torque squeezed out of the engine. Last but not least is the 107ci to 119ci upgrade that adds 23 percent more horsepower and 17 percent more torque.

The new kits are already out, and you can find more information about them on the bike maker’s website. You should note that Harley offers 24-month vehicle limited warranty when the kits are dealer-installed within 60 days of vehicle purchase, or 12 month otherwise.