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Harley-Davidson just released it’s first all-new Big Twin engine in 17 years, the 8-valve Milwaukee Eight, last month. We heard great things about it, but we had to try it to see what all the fuss was about – and what better way to really see how it compares to the Twin Cam, than riding them both back-to-back!


201 harley davidson road glide milawukee eight engine A 2017 Harley-Davidson Road Glide with the all new 107ci Milwaukee Eight engine.


For Harley-Davidson to introduce a new engine is a very big deal.

There have actually only been nine engines in the Motor Company’s entire 114-year history. You already know the names; Knucklehead, Panhead, Shovelhead, and so on, each one not just an engine, but the very heart of entire generations of bikes from the most iconic motorcycle brand in the world. The next engine to carry the Harley name into the future? The newly introduced Milwaukee Eight.

This update comes at a critical point in the Motor Company’s history too. Harley-Davidson has been getting hammered on all sides lately; sliding sales, intense competition, and a slew of recalls and even government investigations have all been chipping away at the mighty motorcycle manufacturer’s reputation in recent years.

But more than anything else, Harley-Davidson has simply been needing to modernize. The Twin Cam, the predecessor to the Milwaukee Eight, had been powering Harleys for 17 model years – a long time by anyone’s standards. It’s not uncommon to hear Harley critics knocking the brand for being “stuck in the past,” but when even the guys with bar and shield tattoos are complaining about why there’s still no new engine out, you’ve got a problem.

That’s why Harley-Davidson really needed to knock it out of the park with the new engine. It had to be a big leap forward, while retaining the brand’s traditional character; modern enough to reestablish Harley-Davidson as a producer of well-engineered engines to a whole new generation of customers, but still unmistakably Harley enough to satisfy the Faithful. Doing one or the other would have been easy; doing both, however, was no small order.

But they delivered the goods. And I got the rare opportunity experience it by testing one of their most popular touring models, the Road Glide – first with the Twin Cam, and then with the new Milwaukee Eight, back to back – to see exactly what the changes felt like first hand.


How Is The Milwaukee Eight Different?

To understand what makes riding Milwaukee Eight-powered bikes such a different experience, let’s briefly dive into what actually makes the engine itself such a big leap forward.

The Twin Cam was introduced in 1999 as an 88ci model, but after powering Harleys for nearly two decades, it’s been showing its age. The upside of an engine in development for that long is that it is very refined; modern versions are either 103ci or 110ci, depending on the model they’re in, and are fine engines, especially after the sweeping Rushmore updates of 2014, still powering a dozen models in the Dyna and Softail line for 2017.


201 harley davidson road glide milawukee eight engine A close-up shot of the Milwaukee Eight engine. This engine is the tip of the spear in Harley-Davidson’s approach drive toward the future.


But the Milwaukee Eight makes massive changes to the Big Twin’s design; not just in its architecture, but in its brain. The main changes made were:

1) Twice as many valves (from two per cylinder to four; eight total.) This is the principal change to the Big Twin’s architecture, and where the “Eight” in Milwaukee Eight comes from.

2) Dramatic improvements in cooling. Engine designers were instructed to make massive improvements in the Big Twin’s cooling ability, which they accomplished by:

  • Eliminating air-cooling, and moving to either oil-cooling, or what they call Twin Cooling (combination oil- and water-cooling) on higher-end models
  • Changing the head design from a rounded, hemispherical design to a flat design, reducing the surface area through which heat can enter the head
  • Faster combustion from 2 spark plugs per cylinder
  • More advanced, more efficient EFI
  • A lower idle (from 1000 to 850)

3) More power, largely as a result of the improvements in cooling. The new design runs so cool, Harley’s engineers were able to crank compression as high as 10.5:1; add that to an 8-valve engine with a 55mm throttle body flowing 50% more air than the Twin Cam, and they were able to crank a lot more power out of the new engine.

4) A combination of counter-balancing and rubber-mounting. To settle the Big Twin’s big vibration, the Twin Cam was either counter-balanced or rubber-mounted depending on model; the new engine uses both, but retains a precisely engineered 25% of native vibration to retain the rumbley feel at a “just right” level.

Ok, now that’s the technical stuff; but now lets get to the good part.


What Does Riding the Milwaukee Eight Feel Like?

To really put the new Milwaukee Eight in perspective, the only accurate way to do it was to do a direct comparison to the engine it’s replacing. Luckily the fine folks over at Sweetwater Harley-Davidson in National City, CA, just outside of San Diego, agreed with me. They arranged for me to test ride two of their finest touring models, the Road Glide, for damn near as long as I wanted – first a 2016 with the 103ci Twin Cam, then a 2017 with the new 107ci Milwaukee Eight. They were so cool, in fact, they even gave both to me in my favorite color: black (insert sunglasses emoji here.)


2017 harley davidson road glide milawukee eight engine Back to back rides – the only way to really test a new engine compared to the previous one.


I started with the 2016. Here I have to immediately say that the riding experience on the high-end touring Harley, even with the “old” engine, was nothing short of spectacular. It’s been a while since I’ve hopped on a Harley; I’ve always had a fondness for the brand, but I have voted with my wallet for imports on my last 7 bikes, and haven’t owned a Harley since my Dyna Super Glide in 2005. I’ve ridden a few friends’ Harleys since, and they are nice for what they are, but have never made my way up the food chain to these top-tier baggers. I have to say though: it is an entirely different experience up here.

Harley has come a very long way in fit and finish in general, but moving up to the brand’s top-of-the-line touring models puts you in a whole new category of luxury. My Road Glide was loaded to the hilt, built like a tank, powerful, and surprisingly maneuverable, and riding it was an absolute joy. The Road Glide was relaxing and refreshing; I could see myself going out for a short ride to get breakfast, but end up rolling back into my driveway at 10pm “just because.” It’s that good.


2017 harley davidson road glide milawukee eight engine This is the 2016 Road Glide with the Twin Cam engine. This is a spectacular motorcycle and the entire bike, including the 103ci engine, is very refined. The new model with the Milwaukee Eight edges it out, but you certainly wouldn’t complain about taking this one home.


But before wandering off too far into the sunset, I had to remind myself that I was there to find out how the 2017 with the Milwaukee Eight stacked up to the Twin Cam. So I headed back to switch bikes, and then hit the road on the exact same route. Here’s what I thought.

First of all, torque all day. The Twin Cam 103 in the ’16 was powerful, but the 107 simply pulled harder, for longer. Thank the extra airflow and the much more advanced EFI system for this; there is torque on demand, wherever you are in the RPM range all the way up to redline, something the Twin Cam simply couldn’t pull off.


2017 harley davidson road glide milawukee eight engine About to head out on a ride – first on a 2016 with the outgoing Twin Cam engine, then on a 2017 with the all-new Milwaukee Eight.


But the stronger impression I got from the Milwaukee Eight was that it was simply much more refined. After 17 years of production, the current Twin Cam in the ‘16s is refined too; but the 107 feels even more so. It is more responsive, has a nice “clean” mechanical feeling, and is noticeably less noisy. The riding experience in the ‘17 Road Glide was equally regal, as much of the bike is unchanged; but the new engine, along with major improvements in the notoriously bad front suspension, made for a better ride all-around.


The Important Question: Should You Buy It

The main takeaway I got from riding both of these bikes back to back is that they are both spectacular machines, and far exceeded my expectations. Harley-Davidson has its critics, and most of their complaints about their bikes are valid ones (I often make them myself.) But one thing they really get right is delivering a world class “cruising experience” on their higher-end bikes. You feel like absolute royalty on one of these machines, and both the riding experience and the commanding presence you feel aboard one is simply unmatched.

Now off the lot, the riding experience of both is close. The current crop of tourers with the modern Twin Cam are surprisingly refined; the engine has come a very long way since the 88’s days, and against the all-new Milwaukee Eight, the Twin Cam wasn’t exactly light years back. The new engine is a better engine in a better bike, but not dramatically so. The 2016 was a nine, the 2017, a ten; one is better, but you would certainly not complain about going home with either.


2017 harley davidson road glide milawukee eight engine Harley-Davidson has it’s areas of needed improvement – but it’s top tier baggers aren’t one of them. Their top of the line touring bikes, like this Road Glide, are exceptional.


But that’s just riding off the lot; not big picture. In the big picture, Where Harley really nailed it with the new engine is in it’s upward potential.

The new engine has a riding experience that is pure, traditional Harley, and none of the Faithful will be put off by it. But look carefully under the hood, and what you’ll find is a truly advanced piece of engineering with a LOT of tuning potential, with a well-designed engine architecture, and an advanced computer system to manage it. The old guard might be put off by this, but like it or not, tapping into engine performance these days requires that you be as handy with a laptop as you are with a wrench, and the new Big Twin is no exception.

This is a good thing though, because this is where the younger generation that Harley needs to recruit will probably have the most fun – squeezing more power out of a well engineered engine, with equal parts installing hard parts and programming fuel maps. Harley-Davidson needed to modernize, we all knew it, and the new Milwaukee Eight is leading the way forward – and it absolutely does not disappoint. The Milwaukee Eight will take Harley-Davidson to the next level – and if you ask me, it’s not a moment too soon.


2017 harley davidson road glide milawukee eight engine You can’t complain about too much when your job is to ride cool motorcycles and talk about them. I had to get a photo with the thing since I couldn’t take it home!


What are your thoughts on Harley-Davidson’s new Big Twin: more of the same, or the beginning of a new era?

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