Added to H-D's Screamin' Eagle performance bolt-on upgrades for 2017 and later twin-cooled M-8 Touring models are these 107 to 128 ci and 114/117 to 131 ci Stage IV kits.
Features of the 128 ci kit include new CNC-ported heads with 1 mm bigger valves than the previous generation, and fully machined combustion chambers, high-lift SE8-517 cam, high compression pistons and a 64 mm throttle body and cast intake manifold - "this combination delivers 126 ft-lb of torque and 121 hp rear-wheel output when paired with SE Street Cannon mufflers."
Additional components include 128 Stage IV timer cover, forged high compression pistons, high performance cam bearing and tappets, 4.31" steel sleeve cylinders and high flow injectors (5.5 g/sec).
On the stock 114/117 ci M-8, this combination delivers a claimed 131 ft-lb of torque and 121 hp rear-wheel output.
Eligible for Custom Coverage under the motorcycle’s factory 24-month vehicle limited warranty when authorized H-D dealer-installed within 60 days of vehicle purchase; otherwise backed by a 12-month limited warranty. Both the 131 ci and 128 ci Stage IV kits comply with noise and emissions standards in all U.S. states other than California on 2017-later Touring models. Neither kits fit Trike models.
2017-’19 models require separate purchase of a high-capacity oil pump; 2017-’18 models require separate purchase of Screamin’ Eagle high-capacity clutch plate kit; all models require additional purchase of ECM recalibration with the Screamin’ Eagle Pro Street tuner.