Is the motor pulley 8 or 10mm?

All of our motor pulleys have an 8mm bore. You can fit an 8mm motor shaft with a keyway (3mm x 3mm). Compatible with all of our motors.

What gearing should I use to do close to 50mph

We do not recommend traveling at these speeds.

Do I need the dual motor or the single motor kit?

It depends. We recommend a single motor setup for most flat road riding. If you are climbing steeper hills 20-25%+, we would recommend a dual motor setup.

If you want more traction or power a dual motor setup is recommended.

on the 218mm torque trucks what size shaft does it have i.e. 8mm or 10mm

Hi,

Our shafts on our 218mm Trucks are 8mm in diameter, same as standard longboard trucks.

If you have any questions, please let us know. Thanks!

Is this product: https://diyelectricskateboard.com/products/single-motor-mechanical-kit for 50 or 63mm motors

Hi,

This product is for 63mm motor mounts. It includes our V7 Motor Mounts.

If you have any questions, please let us know. Thanks!