(1) The speed change locking rod is too short (2) The adjustment cut of the shift fork axle is severely worn (3) The spring elasticity of the locking pin was not sufficient (4) The bearing on the pinion shaft is worn out, the axle is tilted (5) The gear shoe spline is worn out
(1) Adjust the locking rod accordingly speed changes (2) Replacing the fork shaft (3) adjusting or replacing the locked pin spring (4) Replacing the bearing (5) Replacing the gear holder