I am new here, but I have gained a lot of experience with Duke 390 and 690 in the last years with fuelling changes. I run a wideband O2 sensor with datalogging to control my fuelling to prevent any damage running too lean (or loosing power when too rich).
From next season on I will transfer all my experience and electronic stuff to my new Vitpilen 701. As the engines are identical and the exhaust nearly identical, I expect, the my experiences from the Duke 690 will help to optimise the Vitpilen. The only major difference is the airbox, which generally works to the same principal as at the Duke, but has some differences, which are in my opinion an improvement. So is the airfilter in the Vitpilen significantly larger the at the Duke. It is the filter from Duke1290. Secondly I prefere the airbox cover under the seat, so no drilling and cutting at the airbox is necessary to gain more air and power.
I general the 690 KTM engine is very welcoming to airbox modifications, as the airbox is relativ small (compared to the engine size) and noise restrictions for Euro4 take it’s toll. KTM really found a good compromise whith really good top end power, but in low and mid range there is room for improvement.
Exactly this shows the pirates video. Removing the airbox cover improves the amount of air at low and mid range. More air with same fuel will lead to a leaner engine. But as you can see in the graphs at 17:15 in the video, the Vitpilen without cover is still in an execeptable range. Lambda value goes up from 0,85 to 0,9..0,95, which is absolute no problem for a watercooled 4-stroke. Above 1 would be critical. Of course you can gain some more power by correcting the fuel, and exactly this I will do.
There are a lot of experinces about optimising the Duke 690 at the ktmforum.eu. Search for
“Neues aus der Tuningküche – Modell 2016 Duke-V Stage-II & III”
at 690 LC4 Tuning.
I will report later the year about my progress, but at first spring must come and I have to run in the new engine before starting my work…………