My Diamondback Serene Ebike Build

I bought a Step-through Diamondback Serene bike and with an Ebike kit from Calibike, I turned the ordinary bike into an Ebike that turns heads. I love the bike very much and I do get offers to either buy my bike or make one for sale. The bike runs beyond 50/mph. I am scared of finding out its speed limit. I may try to find out its speed limit on the highway.