10 L/100 km is pretty bad, and the rich-smelling exhaust is a confirmation. The appearance of the spark plugs would be another clue.
There could be something wrong, a bad sensor, a dribbling injector, etc.
Check the forums for that bike to see what other people are experiencing and what they are doing with the tuning, if anything, to improve it.
Tuning for gas mileage is more difficult and time-consuming than tuning for power. I've done it (on another bike that had miserable fuel consumption in stock form). Requires installing an air/fuel ratio gauge so that you can watch what's happening in real time and a PowerCommander or something similar so that you can change stuff. My '04 ZX10R used 7-ish L/100 km in stock form, and that gauge revealed that at 90 km/h steady cruise, the engine was seeing 11:1 air/fuel ratio, which is obnoxious, and it was almost as bad at most other part-throttle cruising conditions. It's now 15.0 - 16.0:1 at part-throttle cruise. Big parts of the PowerCommander map are -30% or more. The tricky bit is that there is a fine line between lean-cruise and lean-misfire, and there are certainly conditions in which you cannot run it that lean. Once sorted out, it runs very well, and consumption is now more like 5.5 L/100 km, but it took a lot of fine tuning to get to that point.