I am sorry! I was wrong! You said kph! Not mph! Saw your video and your rpm's are too high relative to speed. Needles confirm what I could figure 100 kph = 62 mph and so on. Too high. Needs fixing!
Yes, I saw your video. That is what prompted me to admit my error. OK, this is what I have observed in my two DT300i scoots:
Level ground, steady speed, no wind
45 mph 72 kph 4500 to 5000 rpm
50 mph 80 kph 5000 rpm
60 mph 96 kph 6000 rpm
70 mph 112 kph 6500 rpm
80 mph 128 kph 7800 rpm
Any speeds lower than about 70 kph you should see about 3500 to 4000 rpm more rpm on acceleration less on trail throttle. The way you are winding up rpm's suggests the variator is not changing much if at all.