Have you personally built, or ride, and maintain a Phantom???...I have two, with the very rare exception of someone who knows exactly what they are doing in order to modify a pipe to a Phantom, like
@ImpulseRocket, forget any modifications like this on a Phantom.
They were purposely designed and made to "scream" right out of the box...Both of mine would hit 51 MPH right out of the box with throttle left over....That is already way too fast for a regular bicycle with a motor attached unless you have a suicide wish.
I cruise at 30 to 35 MPH quite easily with zero effort of having it even begin to breath hard using 1/4 throttle or less to maintain that cruising speed.
Modifications by those who are not really mechanically adept. especially with Phantoms have ruined the Phantoms right out of the box with the faulty thinking they atre just like any other run of the mill China Girl...That, they are not.