From Unofficial Zero Manual
- The motor shaft is keyed; the key has a square cross section.
- Dimensions seem to be ¼” square ⨉ 2.0” length (expressed in metric on drawings).
- Ends 5mm from shaft end.
- Shaft diameter is ⌀28.275mm+0-0.021
- Shaft length extends 66.675mm beyond the motor face minus 4mm for raised parts of the face.
- 2013 models had a minor recall about the shaft key coming loose, but this was a design revision that has not recurred.
- The motor shaft is splined to allow higher torque transmission.
- Rumor has it (via Harlan at Hollywood Electrics) that the spline is supposed to match a Kawasaki KX250F as well as a Yamaha YZ450F.