KTM 790 Duke Road Test: Sharp as a Scalpel, Indisputedly Intuitive

KTM 790 Duke road test: sharp as a scalpel, indisputedly intuitive 1

First ride on the production 2018 KTM 790 Duke streetrod

KTM has made a key roll of the dice with the introduction of the 790 Duke, its first ever parallel-twin launched at last November’s EICMA Milan Show, and now in production at its Austrian base at Mattighofen powered by the all-new LC8c (standing for liquid-cooled eight-valve compact) engine. Its arrival marks the debut of an entirely new middleweight platform for Europe’s largest manufacturer, aimed at making it a contender in the global 501-900cc Roadster aka Naked Bike category. There, worldwide annual sales currently amount to 130,000 units, and are building all the time, with 70% of them in Europe, 19% in North America, and 11% in the rest of the world, where the biggest growth is expected to be – particularly in Asia and South America.


Previously, KTM had only its 690 Duke single-cylinder niche model to compete in that significant segment against the Yamaha MT-07/MT-09, Triumph’s Street Triple in its different manifestations, BMW’s F800R, the Kawasaki Z900 and suchlike. Now, with the 790 Duke twin – aka ‘The Scalpel’ on account of its focused design and pared-to-the-minimum weight and bulk – KTM has a mainstream contender for marketplace supremacy, making this a vastly important bike for the company that at Euro 9,790 in Germany including 19% local tax, is both competitively priced, and highly distinctive. What’s more, in transferring production of this and all other future middleweight KTM – and Husqvarna – models powered by the LC8c engine to China in 2020, KTM president Stefan Pierer will ensure that the 790 Duke, its forthcoming 790 Adventure due in a year’s time, and other later models will be all even more affordable, and well-priced.


With its typically sharp-edged styling by Kiska Design, and available in grey and black as well as the trademark orange, the 790 Duke fills the pretty big gap between the 690 Duke single and 1290 Super Duke V-twins in the Austrian firm’s streetbike range, and in doing so brings an entirely new level of electronic sophistication to the middleweight sector, with features that some Japanese one-litre sportbikes don’t even have. Delivering maximum power of 105 bhp/77kW at 9,000 rpm with a dry weight of just 169kg, it’s a typical KTM in terms of adding performance via reduced kilos. And in addition to a comprehensive and easily readable TFT dash and two-way quick-shifter as standard, it features electronics previously seen only on bigger bikes, including IMU-controlled traction control and cornering ABS.

All-new short dohc eight-valve engine has 75º crank throws with 435º  firing intervals and dual counterbalancers, one in cylinder head, the other off crank

KTM engineers began work on creating the LC8c motor back in 2012, since when the 250 people engaged with the project in the R&D department invested 111,111 man-hours (OK, several woman-hours, too), with 60 of them working full time on it, covering 604,800km of intensive dyno testing and over 900,000km on the open road. KTM doesn’t do things by halves, but even so, the fact that they invested so much time and money in getting this platform right is an indication of the importance of the project to the company’s future growth strategy. 


First, though, they spent two years considering whether to produce a downsized middleweight version of their larger capacity 75º V-twin family of engines, before settling on a dohc eight-valve parallel-twin. “We had to get this right, because it will be such an important platform for us for many years to come,” says Torsten Gaul, KTM’s Head of Engine Street, and the Austrian firm’s head of engine R&D. “But after spending a great deal of time assessing the two formats, it was pretty clear that the V-twin configuration would not work for us, because our main goal was to get the engine as compact as possible. With the V-twin you have limitations regarding the seat height, because the rear cylinder sticks up into the seating area, and the engine is also longer, which means you must have a shorter swingarm for the same wheelbase, whereas we wanted a longer one for better grip. Also, the height of the engine with the throttle bodies between the Vee also brings disadvantages for packaging reasons, so in 2015 we decided to go with the parallel-twin format.”


KTM’s first-ever horizontally-split engine is used as a fully-stressed chassis member, with special attention paid to keeping the 88 x 65.7 mm 799cc motor not only light, but also narrow to help maximise cornering clearance, as well as to suit riders of all heights. “We wanted to make a bike that’s intuitive to ride, that’s light and responsive with the extra performance of a twin, but without sacrificing the agility of a single,” says LC8c Product Marketing manager Adriaan Sinke. KTM was aware that many of their existing customers would be coming to the bike from a single-cylinder model, so wanted to make it look not so different to what they were already riding. Then to go with the firm’s Ready to Race philosophy they wanted to establish a visual link with their Motocross bikes, so all of this meant the parallel-twin concept won out. The fact that it also centralises the mass of the engine, which allowed its engineers to design a more compact, easier-handling motorcycle, was also a key factor.


The result is a compact, lightweight, liquid-cooled dohc eight-valve engine with its crankpins offset by 75º (versus the more common 180º crank throws) with 435º firing intervals to replicate the gritty sound of a KTM V-twin’s irregular firing order, fitted with twin counterbalancers to eliminate vibration as was previously done with the single-cylinder LC4 motor – one at the front of the engine and one in the cylinder head, between the camshafts. These allow the LC8c motor to be employed as a stressed member of the frame, which in KTM tradition is made from tubular steel, with a diecast aluminium rear subframe and an ‘inside-out’ swingarm operating the non-adjustable (except for spring preload, and then only via a C-spanner) direct-action cantilever WP shock giving a substantial 150mm of travel, matched up front by a 43mm upside-down WP fork that’s equally devoid of adjustment, but gives a rangy (by street standards) 140mm of wheel travel.

Six-speed gearbox matched to slipper clutch has wide-open powershifter and clutchless autoblipper for downshifts plus launch control and spin adjuster

The LC8c is tuned as much for midrange torque as top-end power, peaking with 86Nm at a relatively high 8,000 rpm for a parallel-twin, but there’s a broad spread throughout the rev range, with more than 80Nm available at 6,000rpm. There’s chain drive to the cams offset to the right of the cylinders, while the six-speed gearbox allows clutchless quickshifting both up and down the well-chosen ratios, and is matched to a PASC/Power Assisted Slipper oil-bath clutch which is cable-operated for ease of maintenance, and to save weight. The open deck Nikasil-lined cylinders (thus saving the weight of cast-iron liners) are integrated into the upper half of the high-pressure diecast aluminium crankcases, with the lightweight forged one-piece three-bearing crankshaft carrying forged pistons via a sophisticated cracked conrod design, which results in low piston weight and reduced reciprocating mass. KTM has also shortened the engine considerably by stacking the gearbox shafts vertically one atop another, and they’re surmounted by the shifter mechanism which is right under the 42mm Dell’Orto throttle bodies which are fed cool air from an airbox under the seat, itself breathing via twin intakes either side of your hips. The entire very compact engine weighs just 50kg without throttle bodies or oil (53kg with those included), says Torsten Gaul, compared to 41kg for the 690 Duke’s single-cylinder motor on the same basis.


That’s pretty amazing for an 800cc twin-cylinder engine, and you definitely feel the result when riding the bike. After being honoured with a brief getting-to-know-you ride last September on the prototype 790 Duke, the chance to spend a whole day on the grippy (because lava-tarmac’d) roads of Gran Canaria, including a couple of hours riding the island’s Maspalomas circuit allowed a more intensive evaluation. Just as first time around, though, the 790 Duke feels small, slim, short and sporty, with a close-coupled riding stance that has your chin seemingly over the front wheel. It’s a responsive, eager-revving bike that’s not only thoroughly practical but also hugely entertaining, and totally intuitive to ride. It’s one of those bikes where you feel a part of it from the very moment you hop aboard – this could make riding to work a lot of fun, though maybe not half as much as taking the long way home on it….

Action_KTM 790 DUKE MY2018_14

I started out using Street mode out of the four available, before switching to the slightly sharper but stil super controllable Sport map – there’s also a Rain mode with a smoother pickup and, reduced power, plus Track which is sharper still for racetrack use, though even that has a crisp but controlled pickup from a closed throttle that’s not at all snatchy. The LC8c motor pulls cleanly wide open from 3,000 rpm upwards, with a crisp throttle response in both Street and Sport – I ended up using Sport all day even in traffic and tight, twisting mountain roads. It pays to surf that flat torque curve, so short-shifting wide-open at 7,000 rpm rather than the 9,500 rpm redline gives you plenty of acceleration en route to 100 mph/160 km/h on the TFT dash, with the prominently marked gear selected reading always readily viewable at a quick glance. As on its low-cost 125/200/390 Dukes’ instruments, KTM’s dashboards are a model of readability to others. Vibration was never an issue at any revs en route to a top speed of about 140 mph/225 km/h, though Torsten Gaul admits his team deliberately left in just enough to give the engine some character – which it has aplenty. The two-way powershifter is superb, delivering light, positive wide-open gearshifts under acceleration, and equally positive downward clutchless shifts accompanied by a great-sounding autoblipper. I didn’t miss a single gear in a 140-mile/230km day of riding. Economy was excellent during that – I got better than 50mpg (UK) or 5.6lt/100km in a day of hard riding, giving a range of around 150mi/250km from the 14-litre fuel tank.


The 790 Duke’s steering geometry is pretty steep, with 24º of rake and 98mm of trail, delivering a 1475mm wheelbase and that’s probably the reason for KTM to fit a non-adjustable WP steering damper behind the lower tripleclamp. But the Duke’s agile, super-responsive handling is the payoff for that, coupled with total stability on fast third or fourth-gear turns – it feels planted to the tarmac, yet the great leverage from the wide, taper-section 760mm aluminium handlebar lets you carve corners and especially switch direction in fast chicanes like the one at Maspalomas really easily. Like I said, it’s intuitive. That handlebar can be adjusted almost infinitely in search of your preferred riding position – in addition to four different clamping positions offered by the upper tripleclamp’s design, you can also rotate the ‘bar through three different angles to get comfortable with it. Then as well as the stock 825mm seat height, there’s also a lower 805mm seat option available for the extensive KTM aftermarket catalogue, or you can reduce it still further to 780mm via a lowering kit. Thanks to the narrow seat where it meets the fuel tank at 5’10”/1.80m I could put both feet flat on the ground at rest. 


Even though KTM has obviously aimed to keep costs down with the non-adjustable WP suspension, the generous travel is well controlled in everyday use, and after a day spent trying my best to fault their choices, I must admit that KTM’s development team got their settings for it just right. It’s a pity there’s no remote preload adjuster for the shock, though, which would be useful when carrying an occasional pillion – and there’s surprisingly good passenger space on such a minimalist motorcycle.  I’d never ridden on Maxxis tyres before I tried out the 790 prototype, but the Taiwanese manufacturer whose products equip most of KTM’s offroad range have done a good job here with their Supermaxx SP street rubber especially designed to equip the 790 Duke equipping the lightweight 17-inch cast aluminium wheels. The 180/55ZR17 Maxxis rear tyre will be another factor in the nimble handling, too – KTM has resisted going large there, and heavying up the steering as a result.  

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Both the Maxxis tyres and the WP suspension allow the 790 Duke’s sharp, precise and frankly addictive handling to come to the fore in a way I didn’t really expect that they would, and even on the race circuit the front end seemed planted in turns. When the rear Maxxis started to slide it did so very progressively, though on the Track setting at Maspalomas which allows you to adjust the TC in nine increments (or switch it off altogether) I found dialling in level 3 (with level 9 the most intrusive) took care of that. Track mode also has a launch control function which is fun to use, and you can also disengage the TC’s anti-wheelie to make an attempt at emulating KTM’s own trick cyclists like GP ace Jeremy McWilliams in stunting aboard the 790. In my case, a poor copy (thanks for the kind words, Jezza!) – but I had fun trying, and that’s what riding this bike is all about.


The twin 300mm front discs are gripped by four-piston radial calipers from Spanish company J.Juan, whose products adorn World Superbike champion Johnny Rea’s Kawasaki, and these stop the bike well with lots of feel, without using the large 240mm rear disc very hard at all. The settings for the slipper clutch have just enough engine braking left dialled in to help you stop for a second-gear hairpin from high speed, without chattering the rear wheel on the overrun. Plus the settings for the clutchless autoblipper are so ideally chosen that you hardly have to use the brakes climbing a twisty mountain pass– just backshift a couple of times for a slow bend, and the residual engine braking invariably takes care of slowing the bike in normal use. OK, start going for it, and you need to work the lever, but not otherwise. The clutch action is super light and positive when you do have to use it, as I imagine you’d have to riding in town. This won’t cramp up your left hand riding the 790 Duke to work each morning.

2018 03 01 KTM Duke 790 48

Even braking hard at the end of the Maspalomas main straight after enjoying the extra performance of the street-legal Akrapovič silencer available as an option fitted to the bike I was riding there, the 790 Duke remained stable and well-controlled – and the Maxxis front tyre was hard to fault. The Bosch 9.1MP ABS did activate occasionally, but after proving to myself that it did cut in – though not too intrusively – I switched it off as you can do in Track mode only. The non-adjustable suspension didn’t misbehave too much, and you have plenty of warning when the tyres started to approach their limits. 

A very impressive real world ride that’s a true KTM, replete with the brand’s core values

KTM is planning a series of 790 Duke Power Cup one-make road racing series around the world, and I can’t think of a better bike for everyone from newbies to returnees and everyone in between to go and have a weekend of fun aboard, trading elbows on track and revving each other up in the bar at the end of the day. In 100% stock street mode the 790 Duke can be ridden pretty hard in something approaching anger without misbehaving, and it totally fulfils the expectations that something painted orange brings to the party – and at a relatively inexpensive price. Ready to Race, indeed. Chris Fillmore will ride a 790 Duke this year in attempting to double-up on his 2017 Pikes Peak victory gained on a 1290 Super Duke. Don’t bet against him nudging his own track record on the big KTM aboard this Little One That Can!

Action_KTM 790 DUKE MY2018_12

The 790 Duke is a very good motorcycle that sets the bar higher for its rivals in that crowded middleweight category, and it’s in every way a true KTM, replete with the brand’s core values. This is a very impressive real world ride.

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