Yamaha YDX-Moro Rear Shock Upgrade

The Yamaha YDX-Moro isn't well suited for a coil rear shock. As seen below, the leverage ratio isn't very progressive, and becomes regressive in the last 17% of travel. 

Regardless, the tolerances around the Yamaha YDX-Moro rear shock are very tight. Although a RockShox coil shock will successfully bolt up, at full compression the coil will hit the frame. A Fox coil shock or Bomber CR coil shock uses a coil with an outside diameter 4mm smaller than the RockShox, which might technically work but with coil bulging it might still hit.

Yamaha YDX-Moro Geometry

The Yamaha YDX-Moro has a listed actual seat tube angle of 70.3*. However, the seat tube connects well ahead of the bottom bracket, so the effective seat tube angle is significantly stepper. However, they do not list the effective seat post angle. 

The effective seat post angle of the YDX-Moro and YDX-Moro Pro is approximately 74.5*. 

The effective seat post angle of the of the YDX-Moro 05 and YDX-Moro 07 is approximately 75.5*. The angle is steeper for the 05 and 07 because they use the newer PW-X3 motor whose bottom bracket spindle sits 5mm further back.