Roller question!

I have a simple simple question! First of all I live in a small town where many people drive around with their scooters and want to make me know that they drive their 25/50cc scooter 80-120km/h, which I don’t believe. That’s why my question is which realistic vmax can reach a 50ccm3 scooter and how much acceleration and so on does he lose? I always want to know =) The scooter can drive pure theoretically also 150 is clear but my yes realistic, if you can use d en roller e.g. sportauspuff sportluftfilter and what else do I know! Thanks already in advance =) byebye