Harley-Davidson released its newest engine and motorcycle platform, the Milwaukee-Eight, and how it will be standard issue in all of its 2017 Touring family, Christmas came early to the office.

I hesitate to describe the new-generation powerplant as just a motor though. To hear H-D tell it, the Milwaukee-Eight sounds more like an internal combustion symphony conducted by throttle twisting. That’s because the overall goal wasn’t just improving motor performance. Harley looked long and hard at truly upgrading its touring experience, targeting noise reduction, heat reduction, as well as suspension comfort and performance, which we’ll delve deeper into soon. For now, we’re going to focus strictly on H-D’s new powertrain/drivetrain.

I sat down with Alex Bozmoski, Harley’s chief engineer of new products, and Paul James, Harley’s director of motorcycle product planning, to get the full story on the brand-new Milwaukee-Eight.

Talk about the genesis of Milwaukee-Eight.

The genesis was this: It was time. We had the Twin Cam for a long time. We really got as much out of it as we were going to. It’s a great performer, and we still have it in the lineup. When we were going for a new touring platform, we wanted something five steps ahead of the game, not one. When we committed to doing something new, we started with the customer and really did some soul searching. We had customers saying they wanted something like V-Rod. We looked for common ground between what our current customer base wanted and what new customers wanted and we found it. There were opportunities in the beginning for smaller displacement, higher-revving designs, but when you start thinking about Harley’s look, sound, and feel, developing all of that becomes challenging in an iconic touring platform. We started with listening to customers across the planet. We have a very strict methodology. We looked at what would really enhance the customer experience. Design reviews and cross-functional space holders representing service, marketing, manufacturing, and styling came into play. I didn’t even talk about all the features we put in to make Milwaukee-Eight more precise from a manufacturer’s point of view. It’s a short timeframe from when we say what we’re going to do to production. We have about 1.5 million miles on this product already. This is the most heavily analyzed and tested product we’ve ever done.

H-D Milwaukee Eight
The new Harley-Davidson Milwaukee Eight engine in a 2017 touring modelHarley-Davidson

When the program kicked off, we researched and talked with customers around the world. A thousand riders, in seven different global cities, about what they wanted to see in the next generation of Harley Big Twin. And as we compiled that information, we saw some themes emerge about wanting more power for a variety of reasons, including riding two-up, loaded down, back roads, passing power. In addition to that, they wanted a cooler riding experience with less heat. Then they talked about better fit for the rider—air cleaner, primary changes—to enable more fit for more customers. Global customers were coming to the US and renting US-spec Harley-Davidsons and noticing how much more power they had versus the global Harley-Davidsons in other countries. We wanted to address that. We were looking to deliver universal power around the world. Finally, and most importantly, customers wanted to maintain the look, sound, and feel of our bikes. In the end, we did all of those things and developed a powertrain that delivers more power, 10 percent more torque than Twin Cams, delivers quick acceleration, so it’s two to three bike lengths ahead of a Twin Cam at 60 miles per hour and one to two lengths at 80 miles per hour. We achieved better gas mileage, less heat on the rider and passenger, a smoother, more refined feel, less mechanical powertrain noise, created an internal counterbalancer that reduced vibration at idle, and improved output charging to 50 percent for touring riders. The kind of customer benefits we wanted.

Milwaukee Eight
A look inside the new H-D Milwaukee EightHarley-Davidson

What were the biggest engineering hurdles?

Hurdle-wise, working on the next Big Twin is like operating on the pope. There’s a lot of emotion. Most people here have a Harley-Davidson or ride one. Everyone has opinions on what to do. We had open, honest, productive talks all the time and worked as a team to make it happen. From a technical standpoint, thermal comfort was the biggest hurdle. There are so many sources that can go south and so many conditions to consider when dealing with heat in motorcycling, from being in traffic to in a parade, hot out, cold out, crosswinds, and more. Heads get hot, you have cylinder fin radiation, and so on. Wider or thinner tires in front give you different air movement. Shooting the gap with all these models to make sure each is a pleasant riding experience—it’s tough. We spent a lot of time in wind tunnels. We also had some stuff we didn’t put on the final models that was effective. Look at the P&A lineup and you’ll find these items, like the personal fan. We tested all these factors and determined we made so much improvement on the heat management. We didn’t need the fan for thermal comfort. But we still offer it as accessory for those riding in extreme conditions.

Will the Milwaukee-Eight work with ’16 and earlier models?

Milwaukee-Eight won’t work with earlier drivelines. It’s a new powertrain, tip to tail. No interchangeability.

Walk us through the upgrades and cool new stuff. Let’s start with the airbox

We minimized intake and mechanical noise while maximizing the exhaust note. We really were successful at that. It starts with the airbox that has no intake noise. Part of that has been due to its air volume. Also, getting that airbox tucked in closer to the bike gave us the right ergonomics we wanted. It’s a free-flowing, low-restriction airbox.

What’s new about the exhaust system?

It’s part of moving heat away from the rider. The pipes tucked down in a Vee and fall between the transmission and cam cover and then we pushed the catalytic farther back for high-flowing catalytic. So then continuing that path, you have a bigger throat throttle body, moved from 50 to 55 millimeters in diameter, to breathe better.

How did you reduce mechanical powertrain noise, and how are the cover designs “optimized”?

On the cam drive, the Twin Cam was exactly that: It had twin cams. I was part of that design team. Our entire design philosophy for Milwaukee-Eight was to be as minimal as we can. In a sense, we shrink-wrapped the cover around the part. And we tried to reduce the parasitic losses by removing the number of moving parts; we went to a single cam for lower parasitic losses. To make sure this thing was silent and without resonance, we went to a hydraulic tensioner for silence. And so with one cam, a precise chain, and that tensioner, we have a cam drive system that has lower friction, less moving parts, and that’s very silent.

Is that how you reduced powertrain noise?

Yes, that’s how we reduced powertrain noise, but there were other ways as well. We took all of these cases and made sure we analyzed them and made sure they had the lowest noise.

fin detail milwaukee eight
Fin detail on the new Milwaukee EightHarley-Davidson

How does the new head design translate to better fuel economy?

Sensing, for one thing. The Twin Cam used ion sensors. When getting into different riding positions and heat, you can get detonation conditions. Ion-sensing measures charge in the cylinder after combustion at the spark plugs. However, it has a lot of range to it, though. As you start to retard the motor to compensate for those riding conditions, you lose economy. Ion sensing is not as precise as measuring the knock through an accelerometer-based sensor. So we went to precision knock sensors on each cylinder. When we see one knock, we pull back and not pull too much. That helps with thermal management and fuel economy. You also get more output. It’s an important feature. Combined with the new torque-based ECM, you get smooth and responsive power delivery. Two spark plugs per cylinder were added to speed up the burn. This helps dramatically with combustion efficiency. All of it is designed to work together for the right swirl and atomization. The whole thing is designed so that when you get to the throttle grip, you get as much power as it can do because of great control over combustion. Then it goes to the primary delivering power to the transmission in a smoother, more efficient way. Also, the mechanical components were made for sound reduction. On the road, you get a precision sound and feel. Add that to that to the responsiveness of this design and combine it with best in class suspension, you get a riding experience that’s just a lot of fun. One of the interesting design features is the four-valve configuration. We have 50 percent more breathing capacity now. Live analysis was done to the airbox, ports, and so on at the molecular level. Getting the mixture charge in and out as efficiently as possible was a major goal. All of this makes for a more efficient combustion chamber. So now we have one pushrod activating two valves. If you look at the classic design that has this configuration, they put in adjusters. They usually have low adjustment intervals, which are the cost of ownership and a pain in the butt to go in and have stuff done. What we did is that the hydraulic lifters for each pushrod now account for thermal roll from the engine. We have no adjustment. It’s factory set for life. We came up with an arrangement to set for very low lash at the factory and maintain that for the life of the motor. Going a little deeper regarding valves, part of the motor’s ambience is that it sounds like a precision race engine. Part of that is because the low mass valves create less valve-train noise. With less valve-train noise and less cam noise, you get a different experience when you rev it up. It sounds more like a race engine.

New harley motor
New Harley-Davidson Milwaukee EightHarley-Davidson

How does this set-for-life aspect interact with aftermarket products?

We thought of that. If people decide to put in their own valves or seats, we have rocker arms with no adjustment in them for those people as an option. For most people using stage kits from P&A, they can use the kits without tampering with the adjustment.

Tell us about the oil- and water-cooled systems of Milwaukee-Eight

We added oil capacity; all of the engines are precision-cooled. Some models are oil-cooled, and some are water-cooled. The water coolers are very similar to what we have today, but on the oil-cooled it’s slightly different. We changed the design because we changed the heads. There’s a bigger oil pump; we drilled passages through our heads to adequately cool the exhaust valves. The principle behind the oil-cooled system was to avoid over-complicating the look of the bike with radiators and fans, et cetera. Also, the crankcases are the same but 25 percent stronger than its predecessor. We also improved venting; the cases can’t be overfilled with this motor, so you won’t get oil on the driveway. Lots of analysis was done on this aspect.

What improvements did you make to the driveline?

For starters, we retuned the primary. The compensator bearings were changed, and the ramps changed. This is another place where we analyzed the crap out of it. We completely correlated our models with many vehicles. The goal was smooth torque in all conditions. Complementing that, the clutch was changed to an Assist and Slip Clutch. As you apply load, it pulls the clutch together to minimize spring pressure. Less lever effort per foot-pound that way. Whenever you up performance, you need more spring in the clutch. We went with a hydraulic Brembo activation system across the board on the Touring models to offset that. It’s better at the lever ergonomically. Here’s another feature: In a trans-mission, you can get sound at a stop when it’s hot due to freewheeling gears and lash. We addressed that by adding an anti-backlash transmission gear. Now there’s another piece making the bike quiet.

Going to the balancer, that’s an interesting story. Our customers were in love with going to stop signs and revving their motors. That’s part of the Harley-Davidson heritage, but it’s also hard to explain to others coming to our brand that weren’t in love with that idea. People liked doing that because they were used to it. So we added a balancer, albeit with a lot of reservations. We still needed to make sure to have the characteristic Harley-Davidson feel. We started with a 100-percent balancer but that was too smooth. So we backed it down to 75 percent for that feel but not enough to be harsh. It’s enough feel to know you’re on a motorcycle. Also, the flywheel is completely redone. You’ll find we have a competitive advantage regarding parasitic losses. So what we did with the flywheel was to add 20 percent more flywheel inertia without adding an ounce of weight. Typically, our competition is 11 to 12 pounds heavier with an offset design and higher parasitic losses.

milwaukee eight
The new engine! Get used to it, change is good!Harley-Davidson

Tell us about the oil- and water-cooled systems of Milwaukee-Eight

We added oil capacity; all of the engines are precision-cooled. Some models are oil-cooled, and some are water-cooled. The water coolers are very similar to what we have today, but on the oil-cooled it’s slightly different. We changed the design because we changed the heads. There’s a bigger oil pump; we drilled passages through our heads to adequately cool the exhaust valves. The principle behind the oil-cooled system was to avoid over-complicating the look of the bike with radiators and fans, et cetera. Also, the crankcases are the same but 25 percent stronger than its predecessor. We also improved venting; the cases can’t be overfilled with this motor, so you won’t get oil on the driveway. Lots of analysis was done on this aspect.

What improvements did you make to the driveline?

For starters, we retuned the primary. The compensator bearings were changed, and the ramps changed. This is another place where we analyzed the crap out of it. We completely correlated our models with many vehicles. The goal was smooth torque in all conditions. Complementing that, the clutch was changed to an Assist and Slip Clutch. As you apply load, it pulls the clutch together to minimize spring pressure. Less lever effort per foot-pound that way. Whenever you up performance, you need more spring in the clutch. We went with a hydraulic Brembo activation system across the board on the Touring models to offset that. It’s better at the lever ergonomically. Here’s another feature: In a trans­mission, you can get sound at a stop when it’s hot due to freewheeling gears and lash. We addressed that by adding an anti-backlash transmission gear. Now there’s another piece making the bike quiet. Going to the balancer, that’s an interesting story. Our customers were in love with going to stop signs and revving their motors. That’s part of the Harley-Davidson heritage, but it’s also hard to explain to others coming to our brand that weren’t in love with that idea. People liked doing that because they were used to it. So we added a balancer, albeit with a lot of reservations. We still needed to make sure to have the characteristic Harley-Davidson feel. We started with a 100-percent balancer but that was too smooth. So we backed it down to 75 percent for that feel but not enough to be harsh. It’s enough feel to know you’re on a motorcycle. Also, the flywheel is completely redone. You’ll find we have a competitive advantage regarding parasitic losses. So what we did with the flywheel was to add 20 percent more flywheel inertia without adding an ounce of weight. Typically, our competition is 11 to 12 pounds heavier with an offset design and higher parasitic losses.

How did you achieve the improved charging?

For one thing, we increased starter output from 1.2 to 1.6 as product of larger displacement. One of my favorite features is the revamped charging and regulation system. With it, it allows us to make more power. Part of thermal management was to drop idle from 1,050 rpm to 850 rpm. The Twin Cam makes 17 amps at 1,050. The Milwaukee-Eight makes 24 to 25 amps at 850. At 1,050, it’s over 30 amps. What we have is a system that’s better for accessories that keeps you completely out of deficit charging ever, even stopped in traffic.

We changed the design to get the additional amps by changing to heavier windings and more in number and added cooling to the rotor. You can overheat windings with that much power. There are oiling marks all around the rotor that throw oil around the charging system. The new regulator pulls more heavily from the charging system to be more efficient.

How did you improve the covers?

On the primary cover, we drew it in tighter due to minimizing the size of the clutch. That gives us more comfort for a wider range of riders’ sizes. Part of it was also styling. That’s not a symmetrical airbox. It starts thin by the rider and shaped in tandem with the position of the rider’s leg on the bike.

When will this motor go into other production models?

We just introduced our most powerful line of cruisers ever. We’re not talking about future products or intent right now.