One of my workmates has one of these https://surron.co.uk/products/surron-lbx-dual-sport-e-dirt-bike He's upgraded the battery pack and controller and it does 80 mph it's mental. Cost him about £8k so far He came to our house the other day looking very furtive after having outrun a copper on an off road police bike
Problem with them is they are illegal on the roads, only on private land. I doubt you could road register it to make it legal though.
3 hour @ average 20mph range and battery limited to 500 cycles before deteriorating. Great for kids and teenagers, unusable for anyone over about 14 1/2 stone. Andy