（1） Solve the problem of frequent jump gear. Replace the fork shaft positioning spring; Replace the fork shaft; Change gears or shafts. 

（2）Troubleshoot abnormal noises. Change the gear; Replace the bearing; Tighten the loose bolts; Supplement lubricating oil; Change gears or shafts; 

（3） Eliminate the failure of shifting. The main gear should be repaired to the tooth end burr or change gear.