Stop the press! The rumors are true. Harley-Davidson has indeed developed a new engine called the Milwaukee-Eight. The eight valve V-Twin comes in both a 107” version for Harley-Davidson Touring motorcycles and Trikes and a 114” variation for The Motor Company’s top-shelf CVO line. The new valvetrain design comes with an impressive list of proposed improvements – more power, better efficiency, lower idle, less heat, and less noise.
American Iron brass Buzz Kanter and Steve Lita got a chance to speak with Harley’s Product Planning Director Paul James and Chief Engineer, New Products Alex (Boz) Bozmoski about the Milwaukee-Eight for an exclusive American Iron Magazine first look article in Issue #341 that hits newsstands Sept. 13. Additionally, American Iron Editor Lita has already gotten a chance to sample 2017 Harleys with both the 107” and 114” versions of the Milwaukee-Eight, and his first ride review will run in American Iron Magazine Issue #342. Click here for some of editor Steve’s first ride impressions.
Until then, here’s a few of the Milwaukee-Eight’s key features gleaned from the American Iron Magazine article along with the engines’ specs. If you’d like to hear the new Milwaukee-Eight, be sure to check out American Iron’s YouTube channel.
• Because these are touring machines, design emphasis was placed on rider and passenger comfort (vibration), heat control (from engine and exhaust), and functionality (improved electrics and electronics). From what we were told, Harley met these goals.
• While the engine weighs just about the same as the Twin Cam it is replacing in 2017—at least on the touring and trike models—we were told the Milwaukee-Eight is a clean sheet design, going back to a single cam configuration, with pushrod-actuated four valves per head, hydraulic lifters, and dual sparkplugs per head.
• Harley said there are two versions in relation to engine cooling as well, as bikes without lowers will feature Precision Oil-Cooled engines, while bikes with lowers will employ the Precision Water Cooling system, with the radiators housed in the lowers a la RUSHMORE style. Before you get any bright ideas about retro-fitting a Milwaukee-Eight into an older bike, be aware that the engine mounting points have changed.
• The flywheel weight is the same as on the Twin Cam, but Harley has achieved 20% more rotational inertia with this engine. This aids in smoothing the driveline and producing a broad torque curve that pulls all the time. Redline is 5,500 rpm, slightly higher than a Twin Cam. A single internal engine counter-balancer is tuned at 75%, and the engine is rubber-mounted for less overall vibration to the rider and passenger.
• The heads have been treated to advanced combustion design and flow work, generating almost a 50% increase in flow. The intake and exhaust valve diameters are 40mm and 32mm respectively. Add the dual sparkplug (two per cylinder) design for a more complete burn, and you can see that this is not just a warmed-over Twin Cam design. There’s a new four-post-coil ignition with torque-based ECM with active knock sensors. There is independent control of the front and rear cylinder firing, with the front two coil outputs firing together and rear two firing together. Sequential Port Fuel injection is retained with a single throat inlet throttle body made of plastic. A bump up in compression ratio to 10:1 (107″) or 10.5:1 (114″) from the Twin Cam’s 9.7:1 means premium-grade fuel will be required.
• The single camshaft is utilized for its lower friction qualities, and it is chain driven. Thanks to a hydraulic lifter to pushrod connection from cam to rocker arm, you will never have to adjust the valvetrain from left to right, as they are now factory-set for life!
• It’s larger, more powerful, offers quicker acceleration, and produces 10% more torque. It should prove to be two to three bike lengths faster from 0-60 mph and one to two bike lengths faster from 60-80 mph in top gear.
2017 Milwaukee-Eight Engine Specs:
Engine: 107″ 114″ TC 103 rubber mount
Cylinder angle: 45 degree 45 degree 45 degree
Bore: 3.937″ 4.01″ 3.875″
Stroke: 4.375″ 4.5″ 4.374″
Compression: 10:1 10.5:1 9.7:1
Valvetrain: Four valves per cylinder Two valve per cylinder
Ignition: Four plug four coil Two plug one coil
Torque: 114 ft-lb. @ 3250 / 124 ft-lb. @ 3250 / 104.7 ft-lb. @ 3250
Starter: 1.6 kw 1.6 kw 1.2 kw
Charging system: 24-25 amps / 24-25 amps / 17 amps
Fuel system: ESPFI ESPFI ESPFI
Oil capacity: 4.5 quarts / 4.5 quarts / 4 quarts
Idle speed: 850 rpm / 850 rpm / 1050 rpm
Harley-Davidson’s Big Twins over the Years
F-Head (JD) 1914-1929
Twin Cam 1999-present