May062013May 6, 2013September 19, 201372Commentsby Adam Wheeler

Duke 390 Launch blog Part 4: Little bike with the big heart

Posted in Bikes

The Duke 390 will soon go on sale through markets around the world where KTM is represented. In the wake of the recent launch of the bike we asked product manager Jörg Schüller a couple of questions about the newcomer…

Jörg Schüller, KTM Produktmanager Street. // Jörg Schüler, KTM Product Manager Street.

In the early stages was the Duke 390 originally designed as a sister model to Duke 125/200?

Jörg Schüller: That came a little later. It was clear that there would be a 390, so the chassis was designed from the beginning with regard to the extra power but the final schedule of when the model would come on the market was set at a later time. It was not easy to find a cubic volume that was appropriate for all markets.

Is it harder or easier to build a motorcycle with that ‘global’ view?
JS: As you can imagine it’s difficult because you need to consider more requests and requirements. For different purposes, different cultures, different customer wishes, different riders and different laws and specific homologations. You do not build a Duke just for Austria and then say, ‘okay, let´s go on sale in Egypt or Brazil as well’. Many aspects and considerations have to be considered which can be very particular and therefore not so easy to fulfil.

The frame of the 390 is also used with the smaller Duke models…
JS: Yes, the frame of 125, 200 and 390 is completely identical, including the engine mountings. This chassis carries the typical KTM ‘handwriting’; this now common design architecture reaches back to the ‘Stunt’ concept bike that was shown a few years ago at the Paris show.

The 390 engine had a completely new design. How long did it take to develop?

JS: Two years. It is a very modern DOHC four-valve design with forged pistons and Nikasil cylinder coating. The high-pressure cast aluminium housing makes it possible to realise fine wall thickness. The rocker arms are made of aluminium and DLC-coated, these are very light and good for high revs. DLC stands for Diamond-Like Carbon – a carbon coating – that minimises friction and wear. As with the RC8, the oil circuit is equipped with two pumps – a pressure pump and an evacuation pump. Everything on this engine is carefully geared for optimal performance, low friction and low emissions.

If one looks closely, the engine hangs pretty deep in the frame…
JS: The engine build is naturally larger than the smaller engines, although it is relatively short stroked. The packaging is such that the transmission is placed higher so that output shaft is in the same position as with the 125/200 engine. The gearbox is of course a bigger sized unit and the crankshaft with more inertia sits lower than in the smaller engines.

What differences are there with the Duke engine to, say, an EXC engine?
JS: I am responsible for road bikes, not for off-road. But I guess you can say that the EXC engines are designed differently, more as competition engines and closer to the limits of engineering. The Duke engine develops 44 horsepower, the EXC engines about 55 to 60hp. Also the new 390 unit has significantly more flywheel mass which prevents hacking on the chain at low speeds in high gears.

Since January 2013, we have the A2 class ruling along with new riding licence parameters. Was the Duke 390 designed with these new regulations in mind?
JS: Sure. With this new 35kW/48hp class we decided to get as close as possible with the engine power to put ourselves in a favourable position for the European markets.

The Duke 390 has a dry weight of 139 kilos and 150kg fully fuelled, so with 44 horsepower it is almost too light for the new A2 driving license regulations because a certain ratio of weight and power must not be exceeded…
JS: Yes, but because the power can be reduced about 2hp with a throttle-stop-limiter which can be installed at the dealership quite easily, then the 390 Duke perfectly fits the new regulations. This does not take away the fun factor from riding at all.

The footrests have quite a sporty position…why?
JS: Because it’s a KTM, which can and should be sporty. If you place the footpegs further forward then it presents riding problems because there is not good contact with the knees. It is not so easy to define a generic seat position that fits smaller as well as taller riders but I think we have a very good solution to please everybody.

A nice detail is the Fatbar handlebars. We hear that this is made through a special production technique…
JS: The Fatbar handlebar is silver and looks like aluminium but is actually made of steel. In production a straight steel pipe is filled with water and pumped up under high pressure to the fat-bar dimensions and simultaneously bent. The method is called ‘hydroforming’ and corresponds to what Akrapovic does with their header systems. Also this particular technique is used in the bicycle industry to achieve special frame types.

The symbols on the switch units for turn signals, high beam, electric start, etc. are illuminated, where did this idea come from?
JS: That’s nice, isn’t it? The 125 and 200 have this already. This feature we have installed by special request from our partners Bajaj. Whether such a thing is common in India, I do not know. But I know that many people think that illuminated switches are very cool for us too.