Yes, you could custom install a variable speed controller and then use the 3-wire throttle with it. This will upgrade the scooter from single speed to variable speed.
In around 3-4 weeks we will have a plug-and-play variable speed controller that fits the Razor E300 version 11 and 13+ scooters which are the scooters with single speed controllers like yours. Once we get these new controllers in stock then they will be plug and play with the scooter except for it original throttle, and a 3-wire variable speed throttle or 4-wire variable speed throttle with battery indicator light can be plugged into it.
Hi Robert. The SPD-24250 is not plug-and-play with the Razor E300 scooter. To convert a single speed E300 scooter into variable speed requires a kit that we sell which includes a throttle, controller, and wiring adapters.
Here is a variable speed plug-and-play kit that we carry for the E300 scooter: