2018 KTM 390 Duke Long-term Review

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Approximately 9,000 miles’ worth of freeway, side streets, twisties, and even some…dirt roads? This 2018 KTM 390 Duke has proved to be dependable through it all. (Jeff Allen/)

Buying a personal motorcycle can be a tough decision, especially considering the 300-plus motorcycle models available on the market. You may consider price, power, style, reliability, or perhaps even a riding experience. While I was considering my options for my personal bike, the KTM 390 Duke hit the main criteria for me: low price, unintimidating, and fun. Riding the 390 for a charity ride a few years ago also helped seal the deal for me. The combination of freedom and supporting a good cause in two-wheeled fashion hit all the right feels, so I just had to buy one. After purchasing my 2018 KTM 390 Duke brand new from the dealer in March of 2019, the bike has accumulated nearly 9,000 miles’ worth of daily commutes and weekend rides.

If there’s one thing the 390 Duke loves, it’s corners. (Jeff Allen/)

Where Has It Been?

Since March 2019, these miles included primarily the daily commute of highway, freeway, and side street riding as well as weekend rides around the local twisties and even some dirt roads as part of Motorcyclist’s Alley Rally. No trackdays, no dragstrips, just the humble plebeian roads for this Duke. I measured this mixture of rides to produce an average of 52.04 mpg from the 3.6-gallon fuel tank.

Regardless of whether I was on the freeway or the canyon roads this small naked bike is comfortable, despite the lack of wind protection, and its ergos place you in an upright position to allow for many consecutive hours of riding. I agree with our test rider of the 2017 390 Duke in that at 6 feet tall I too feel right at home in position and shorter riders can easily reach the ground as well. Seat height is a Cycle World-measured 32.1 inches for an easy step down to pavement.

Say hello to new Dunlop buns. (Jeff Allen/)

A big feather in the Duke’s cap is its maneuverability. It has a short wheelbase (claimed 53.4 inches) that makes it a blast in the corners. Its CW-measured 362 pounds is incredibly tight-turn friendly and makes slow maneuvers a breeze. I am impressed by the long life of the stock Metzeler Sportec M5 tires—they did, however, need to be replaced at 8,730 miles. I swapped in some Dunlop GPR-300s (110/70R-17 front, 150/60R-17) to experience a different set of rubber, and although the front’s aspect ratio is smaller than the stock 110/90R-17′s this difference resulted in a quicker initial turn-in and more feedback from the front.

Has Thee Fared Well?

There are many components of the machine that have withstood the test of daily wear in the Duke’s 20-month life.

I have always been very confident in the bike’s ability to start right up at the push of the electric starter, and analyzing the 12-volt lead-acid battery now, it hasn’t discharged or corroded at the terminals and still buzzes to life in cold- or hot-weather conditions. Other electrical components powered by the voltage, such as the TFT display and LED lighting, also work well and have not needed any attention.

The sleek LED lighting has not had any issues. (Jeff Allen/)

The upright handlebars and grips are in good condition with only minor wear at the inner end of the grips. Both the pilot and passenger seats have maintained their form and provide hours of riding comfort. The only complaint I have is that the pillion can be a little uncooperative when reinstalling on the bike.

Seat cushion remains firm and comfortable. (Jeff Allen/)

The WP suspension is also a durable survivor that has made the twisty roads a blast and provided great comfort over even the dirt roads of the Alley Rally. The fork seals have held up well and are not leaking even after all this time.

The brake pads are also still kicking with only the front brake pad showing middle-aged signs of wear. Brake fluid is also clean.

Graphics and paint remain vibrant. (Jeff Allen/)

The plastics and decal graphics prevail with bright and vibrant colors—no fading or peeling despite being left in the sun during work hours. When not at the office it’s stored in a parking garage.

What Needs Some Attention?

While the KTM 390 Duke has seen great success in its 20 months of use, there are a few points that demand attention.

Within the first 515 miles, I had an issue with the engine temperature skyrocketing and warning lights illuminating while on a commute home from work. I was familiar with the overheating history of KTMs, but was still shocked that I had the issue so soon after my purchase. What it came down to was the radiator fan’s 10A fuse blew out and as a result the radiator fan was off-duty. After realizing the fuse was blown I spent around $6 for a multipack of 10A fuses and, since the replacement, have not had any issues and the engine has been running perfectly since.

The TFT dash is arguably one of the best in the biz—that doesn’t mean it lacks idiosyncrasies. (Jeff Allen/)

I have become pretty spoiled with the easily readable full-color TFT dash, however, a problem has surfaced with the clock. It starts to time travel incrementally back in time and has needed to be reset twice—I’ve gone back to the future with no flux-capacitor-equipped DeLorean needed, only a somewhat faulty TFT clock display. Another minor aggravation is the menus are confusing to navigate. Info, Motorcycle, Settings, and Preferences tabs all sound like they could potentially lead you to the same thing, so to this day it still takes me a couple of tries to get to the correct setting screen.

I love and hate living by the water. Despite the bike being covered and under the garage, the moisture in the air takes its toll on the sensitive metal parts. (Jeff Allen/)

Another one of the main complaints I have is regarding the amount of corrosion that has taken hold of a majority of the hardware and the front brake disc (oddly the rear brake disc is not compromised). And this comes down to storage. I live near the ocean, and even in an underground garage with a cover blanketing the Duke, the salty moisture has still wreaked havoc on many of the bits and bobs. I did take some Scotch-Brite to the front brake rotor about a quarter of the way through its current mileage. This removed the grittiness, but the corrosion has returned and is in need of another scrubbing.

Some corrosion on the lower end of the fork tubes was also noticed. The speckling was able to be cleaned a little bit, but corrosion remains. A handful of fasteners on various areas of the bike are also showing the signs of battling the coastal elements.

The corrosion on the front brake rotor makes me cringe. A Scotch-Brite pad has been used in the past and will be needed again in the near future. (Jeff Allen/)

Mechanical pieces like the shift lever and rear brake pedal are sturdy and bearings are unimpaired for smooth shifting and braking actions, however, the clutch lever and brake levers did have play at the perch and adjuster—the clutch’s being more noticeable now that the bushings have worn by countless squeezes. The clutch freeplay has also needed adjustment as the plates have worn, but there is no sign of chatter or slip.

It was time for a chain and sprockets replacement. The new kit was purchased for $156.60. (Jeff Allen/)

The chain has also had a nice long life spinning around sprockets. I have had to adjust the chain tension three times (at 2,400 miles, 7,086 miles, and 8,231 miles) and standard wear on the chain and sprockets now requires its first replacement at 8,730 miles. The chain had about 40mm of total lateral motion so I have replaced it with a D.I.D 520 X-ring chain. The new rear sprocket is 43 teeth and the engine sprocket 15 (stock was 45 teeth and 15 teeth, respectively). The two-teeth decrease on the rear sprocket makes the final drive ratio taller, causing the Duke to have a theoretical increase in top speed, but decrease in acceleration. The benefit in real-world riding is lower engine rpm at the quicker pace of freeway riding, for example, but slightly reduces acceleration getting off the line on city streets. The kit was purchased from Sprocket Center for a total of $156.60.

My 2018 KTM 390 Duke’s dyno chart. (Michael Gilbert/)

After its tires, chain, and sprockets were swapped, my Duke took a spin on our in-house dyno; 40.40 hp at 8,910 rpm and 25.39 pound-feet at 7,050 rpm were recorded. When Cycle World ran the 2019 press unit on the dyno it produced 40.53 hp at 8,850 rpm and 26.10 pound-feet at 6,920 rpm. That’s not much of a difference in performance after 9,000 miles.

The old air filter fins were bent and dirty. Now, a new air filter took its place. (Jeff Allen/)

The airbox was also in good shape and free of dirt. There was a small hint of oil but not enough to collect in the airbox drain. This amount of oil looks to be via crankcase venting. The air filter was blackened and the fins a bit deformed, so that part has also been replaced at 8,730 miles.

Aside from the regular oil changes, there were a couple of points when the oil needed to be topped off (one time in between the 515- and 4,359-mile services and again around 8,000 miles), and at 8,730 miles the coolant needed only a couple ounces to fill it up.

Related Content: The Importance of Working on Your Motorcycle

Regardless of the pros and cons, the 2018 KTM 390 Duke hasn’t stopped making me smile, but with a pride of ownership comes a cost of ownership and thankfully the Duke’s is a reasonable $6,933.95 thus far. At the time of writing, the 9,300-mile service is still needed and that will include things like replacing the spark plugs and changing the engine oil and oil filter—if the first two dealer services are any indication, it will be an additional $250–$270 charge approximately.

Cost of Ownership

Purchased new at dealership in March 2019	$6,000
Fuse   replacement (multipack)	Approx. $5.59
Break-in   service at dealership	$247.67
Second   service at dealership	$271.21
Dunlop   Sportmax GPR-300 (110/70R-17) front tire [WPS Catalog]	$94.95
Dunlop   Sportmax GPR-300 (150/60R-17 rear tire [WPS Catalog]	$133.95
Sprocket   Center chain and sprocket kit	$156.60
Air   filter	$23.98
Total:	$6,933.95

The 390 Duke is an affordable bike that has withstood miles of various riding scenarios and I anticipate many more. (Jeff Allen/)

2018 KTM 390 Duke Specifications

Purchased Price:	$6,000
Engine:	373cc, DOHC, liquid-cooled single-cylinder
Bore x Stroke:	89.0 x 60.0mm
Transmission/Final Drive:	6-speed/chain
Cycle World Measured Horsepower:	40.40 hp @ 8,910 rpm
Cycle World Measured Torque:	25.39 lb.-ft. @ 7,050 rpm
Clutch:	Slipper clutch in oil bath; mechanically operated
Fuel Delivery:	Electronic fuel injection
Frame:	Steel trellis
Front Suspension:	WP 43mm inverted fork; 5.6-in. travel
Rear Suspension:	WP suspension; 5.9-in. travel
Front Brake:	4-piston caliper, 320mm disc
Rear Brake:	1-piston floating caliper, 230mm disc
New Tires, Front/Rear:	Dunlop Sportmax GPR-300; 110/70R-17 / 150/60R-17
Wheelbase:	53.4 in.
Cycle World Measured Seat Height:	32.1 in.
Fuel Capacity:	3.6 gal.
Cycle World Measured Wet Weight:	362 lb.

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