Hey and welcome,
The 2012+ models are not configurable with the TuneECU software, that's the first thing to know. The previous Duke 690 models were and it's easy to get confused. 2012 is the year the bike changed most significantly in recent times.
If you're coming from a 390 you will likely be impressed.
Things to note that I didn't think I'd care about but eventually did and spent money on:
- Crash bars and fork sliders are very useful since this bike 'crashes well' with those bits on and can get torn up without them. $200-400
- Stock suspension sucks on the non-R model, I got the rear R shock and it's much better $500-1000
- Changed sprockets for better city riding, more torque and control in 1st and 2nd gears $60
- Got the upgraded powerparts seat, the stock one didn't bother me but the upgrade became available at a good price and it is indeed nicer $100
- After having an aftermarket exhaust on it without any changes to the mapping I will need to get a Power Commander V or Bazzaz (or other ECU piggyback system) and have the bike tuned. Without a proper fuel and ignition map an aftermarket exhaust results in a noticeable loss of power before 5,000 RPM. Right at 5k it starts pulling much harder. With a proper fuel and ignition map the bike pulls hard and smooth throughout the rev range. $320 for the unit, $200-500 for the tune
- Airbox modifications once the Power Commander V is on the bike in order to allow more air into the engine and make more power, complementing the exhaust upgrade. Free if you cut up your own airbox, $120 if you get a DNA S2 cover, $60-240 if you get another airbox (the range is because eBay vs. new).
- Some people drop a performance camshaft in the engine, netting even more power and fun. This requires flashing the Duke's ECU which only KTM dealers can do, and that ability is scarce in some parts of North America. Cam is ~$200, flash varies based on what dealer feels like charging, apparently
After that it's really just a matter of keeping fuel, oil, brakes, and tires fresh. If you don't care about the weird powerband hole before 5k, and if the suspension and gearing doesn't bother you, you can ride the bike without all those things and be very happy with it. I certainly didn't complain about the bike before those upgrades! :smile2:
Valve adjustments and checking the rockers are the biggest things with the LC4 as far as I can tell. Both are easy to take care of.
Oh and lots of people have their fuel tank warp at the filler hole, causing some venting and in the worst case, some leaking fuel when the bike isn't upright. There are many threads here about that. It's not an end of the world kind of thing but it does happen. A tank is $150 or so on eBay if it's a bad enough problem and KTM doesn't replace it for you for free.
Also some radiators spring a leak in the upper right corner. That seems to be one of those things that either happen or don't.
On that note, the coolant reservoir and the radiator cap is weird on our bikes and can lead to coolant overflowing when the bike gets really hot. That's 'normal' and not something to worry about. Fixes include topping up after that happens, or letting it overflow until it settles at a level the bike is happy with, or getting a new radiator cap which may relieve pressure earlier.
All in all it's a fantastic bike and TONS of fun. Really nothing to be concerned about. If it feels good while riding then it's fine. There are a bunch of ways you can put money into this bike to make it better and better, but even stock it is a guaranteed smile machine. If you like it, get it.