Frequently Asked Questions About Lumpheads

Here are the most frequent questions and answers about the new motor and how it’s different than the Twin Cam  engines in previous model year motorcycles.

Are all Harley-Davidsons going to have this new motor?

Not yet.  For this year, the New Milwaukee-Eight (aka the “Lumphead”) engines will power every 2017 Harley-Davidson Touring and Trike model. The eight-valve motor will be offered in two displacements and three variations:  Milwaukee-Eight 107 (107 CID, 1750cc) featuring precision oil-cooled cylinder heads for the Street Glide/Street Glide Special, Road Glide/Road Glide Special, Electra Glide Ultra Classic, Road King/Road King Classic and Freewheeler models. There’s also  a Twin-Cooled Milwaukee-Eight 107 (107 CID, 1750cc) which features liquid-cooled cylinder heads.  That motor will be found in the Ultra Limited/Ultra Limited Low, Road Glide Ultra and Tri Glide models. A Twin-Cooled Milwaukee-Eight 114 (114 CID,1870cc) which has liquid-cooled cylinder heads, will power the CVO Limited and CVO Street Glide models. Dyna and Softail models will keep the Twin Cam motor for 2017

Will we still enjoy the performance we have come to love from the Twin Cam?

Hopefully it will be even better!  Harley claims that the new 107-inch Milwaukee-Eight engine produces 10 percent more torque than the Twin Cam engine it replaced in the Touring models. In addition to increased displacement, the Lumphead features a higher compression ratio and four-valve cylinder heads (two intake valves, two exhaust valves per cylinder.) The new valve arrangement gives the  motor 50 percent more intake and exhaust flow capacity. The valve train requires no adjustment as the design of the rocker arms enables valve lash to be set at the factory for life. Which is factory-speak for “we’re still using the same hydraulic lifters that the Twin Cam’s had since 1999.” Dual spark plugs for each cylinder contribute to more-efficient combustion. A single chain-driven camshaft is lighter, mechanically less complex and creates less friction and noise.  “The Milwaukee-Eight retains the classic Harley-Davidson 45-degree V-Twin design,” said Alex Bozmoski, Harley-Davidson Chief Powertrain Engineer, who led the Lumphead development team. “It also retains the power characteristic that is the real legacy of the Harley-Davidson Big Twin: strong low-end torque with a broad, flat power curve through the mid-range that’s ideal for the Touring motorcycle rider.”

Will the Lumphead accelerate better than the Twin Cam?

The Lumphead weighs the same as the Twin Cam motor, so all of its extra power contributes directly to improved acceleration performance. The 107 inch Milwaukee-Eight  accelerates 11 percent quicker 0-60 mph and 11 percent quicker 60-80 mph in top gear than the Twin Cam High Output 103. The Milwaukee-Eight 114 accelerates 8 percent quicker 0-60 and 12 percent quicker 60-80 than the Twin Cam 110.

Will improved power mean a reduction in fuel economy?

The improvements to the Lumphead’s heads, including the use of four smaller valves and two spark plugs per cylinder, are said to deliver to up to 11 percent better fuel economy, depending on displacement and model, and a corresponding increase in range.

Hopefully the Lumphead will run cooler than the Twin Cam???

Harley-Davidson knew that the heat pouring off the Twin Cam motors was making riders and passengers unhappy. Interestingly, changes implemented in the Lumphead that make it more powerful also help it to run cooler. Step one to less heat; reduce the amount of heat that’s created in the first place. The Lumphead has a much flatter combustion chamber and lots more openings (thanks to the four valves) than the Twin Cam. A flatter chamber has less surface area to absorb combustion heat, and the 50% greater flow of the four valves lets more air move through the head, getting all that hot air out of the way more quickly. The new head design and dual plugs also allow the actual combustion (burn) time to be shorter, which creates less heat. (Hey, the quicker the fire’s out, the cooler it’s going to be, right?)

The second step to a cooler motor is getting rid of the heat that was created. The liquid cooling of many of the Lumpheads is an obvious way to remove heat. On the air-cooled versions, more effective oil circulation, a stock oil cooler, and larger cooling fins help keep radiant heat away from the rider. Finally, the exhaust system—yes, there’s still a cat, sorry—has been re-routed a bit to reduce the amount of exhaust heat felt by the rider and passenger

Have there been any changes that will make the Lumphead bikes friendlier to smaller riders?

A new, slimmer primary cover and the low-profile shape of the air cleaner cover provide an easier reach to the ground for many riders. All Milwaukee-Eight models are fitted with an Assist and Slip Clutch with increased capacity and new hydraulic actuation that reduces clutch lever effort by 7 percent.

What about taller riders who feel cramped on the current models?

The air cleaner has been redesigned with a low-profile shape that provides more legroom for taller riders.

Does the Lumphead use rubber mounting or counter balancing to control vibration?

Actually, it uses both! The rubber-mounted Milwaukee-Eight engine also features a single internal counter balancer that cancels 75 percent of primary vibration at idle for a more-refined feel and more-comfortable experience for rider and passengers while retaining the classic character of Harley V-Twin engines.

With the tightening EPA regulations, has the Lumphead exhaust  gotten even quieter?

Apparently  not. Many of the changes to the motor have resulted in less mechanical noise from the powertrain. Since the EPA measures ALL the noise coming from a motorcycle, not just the exhaust sound, a reduction in engine noise meant that the exhaust could be allowed to produce a little bit more volume. Not much—drag pipes it is not—but a little is better than nothing. Actually the factory is not claiming “louder’, just “richer.”

Have there been any changes to the charging system?

The Lumphead has a new alternator and regulator that are claimed to deliver 50 percent more output to the battery at idle to better support the power demands of Touring riders, including accessory lighting, performance audio, and heated gear and other accessories. The battery remains the same reliable AGM used since the late 90’s.

Will the Lumphead have the same service needs as the Twin Cam?

Looks pretty similar; the Lumphead has the same hydraulic valve train, which needs nothing in the way of service until something breaks. The liquid-cooled models will need the coolant changed periodically, and of course the brake fluid (Dot 4) that’s been in use since about 2005 should  be changed every two years. The one big change from the Twin Cam is that second pair of spark plugs.  The factory recommends changing the Lumphead’s spark plugs every two years or 30,000 miles, whichever comes first. Now THAT’s going to be pricey, since the second spark plugs are nestled into the cooling fins waaay up on the very top of the heads. The gas tank needs to come off to change the front plug, and access to the rear plug is probably complicated by the backbone of the frame.

How does the new engine look? Does it still look like a Harley motor?

As always when Harley rolls out a new engine, the visual changes to the Lumphead are subtle. Yes, the cam chest, primary cover and rocker boxes are different, but plop the motor next to a 1960’s Shovelhead and the lineage is immediately apparent. The important functional changes like liquid cooling, combustion chamber shaping and so on have left very few visual cues on the outside of the motor. They have been cleverly concealed—just like the second spark plug.

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