Well you're in the same boat I was in, in December. Top speed lagging, range down to 60%? Probably not the motor unless you're noticing intermittent cutouts.JoePah… I'm starting to notice my 4'ish year old rear mounted battery on the '10 Velociti getting weaker. I intend to parallel a 46v range Lithium battery pack, or have the original battery case rebuilt using 18650 lithium cells for around 46v output. This way I can get the speed up to around 22/23mph. Not sure if the internal hub controller could take 50v, so I could then run around 25mph.
There is a guy on ES that removed his stock internal controller and installed a sensor-less one outside, on the bike, so he could run @ 72v's @ around 38mph! He first just serial connected his internal battery and his rear mounted battery (36v+36v), then decided to stuff lithium 5s packs in the original battery case.
The other option I was thinking is to located the UM 48v outside battery pack & their 800watt rear hub & do an upgrade for around 30mph runs!