I put a 48v-2000w motor/lithium battery upgrade.
It also has a new controller (computer) new motor and tire sprocket, new chain, keyed entry so nobody can just drive off on it like the stock ones. Brand new front and rear tires (and inner tubes, with a spare tube which will go with the bike)
Everything was installed this past summer with limited hours driving it. Has a battery level meter on key entry.
Has a top speed (has speedometer) of 31 which isn't too crazy for kids this age, and the top speed can get up to around 40 if you change the sprockets again.
Now the "why sell it"
Well just as luck would have it about three weeks after we completed this build our town of Barrington made all e-bikes illegal to drive.
My son got himself an Ausom brand scooter as well.
Bottom line it was all just put together toward the end of summer and had no driving issues other than him popping a tire which had been replaced.
I do have the original ferrings or plastic covers that cover the battery area but my son wanted people to know it was modded, so they can be put back on with a little fab work.