What are the reasons for not being able to engage first gear?

[RyderFitz]

1. Faulty positioning ball head: It may be that the positioning component of the gear lever's positioning ball head has failed, allowing the gear lever to rotate freely around its own axis and making it impossible to accurately control the gear position. Alternatively, the spherical working surface at the lower end of the gear lever may have worn off, preventing the gear lever from controlling the shift fork or the shift head's groove, making both gear engagement and disengagement impossible. 2. Clutch failure to disengage: It may be that the clutch cannot fully disengage, although the gearbox's shifting mechanism is functioning normally. This issue can be resolved by adjusting the clutch or replacing certain clutch components to achieve the appropriate free play and disengagement clearance. 3. Damaged shift fork: The shift fork may be loose, severely bent, deformed, or worn. In this case, the gear lever's movement reaches the correct position, but the shift fork's movement does not, resulting in severe impact and failure to engage the gear. The gearbox cover can be opened for inspection and repair, and the shift fork may need to be replaced if necessary.