Cheap esk8 build dual 270kv 6s

I was first very intressted in e-bike and was going to build one. But when i saw esk8 on youtube i knew i had to build one first. I bought a longboard in local store and ordered a cheap motor/truck kit on ebay.

So far i have only tested one 5065 and 4s lipo that i had for my rc cars. I manage to cruise in 20km/h and my weight is 100kg!

Build spec: Longboard 8,25x33" Mini Receiver 2x N5065 270kv 2x Rc car 120A ESC 1x MultiStar High Capacity 12000mAh 6S 10C Multi-Rotor Lipo Pack 7" Truck 80mm black wheels


One question to get full throttle i have to increase the throttle trim on reciever to max to get the last speed, why is that? When i stop the th trim has to be lowered so it stands still… Any advice?