From a legit seller

[Rye]

What motor do I buy to make my razor ecosmart electric scooter faster

 

[addertooth]

These do not have very many performance modifications available. I think someone may sell a kit on eBay.
Is your the 350 Watt version, or the 500 Watt version? The 500 Watt version goes about 3.5 MPH faster, at 18.5 MPH.
These are 36 volt lead-acid battery scooters, and were never really intended for high speeds from the factory.

 

[HumanPerson]

https://electricscooterparts.com/