We recently updated the instructions for the G4 belt drive with a new video on our youtube channel. You can also find a link to it on our website on the instructions page.
The installation of the bottom retainer into the drive shaft has been particularly difficult for some customers. To help we created a detailed video that shows the exact process to complete this task. If you have any questions about how to complete this step or any others when installing your belt drive please do not hesitate to reach out to us directly.