乱挡是手扶拖拉机常见故障之一，常规排除法都要先拆掉牵引框或变速盖后再进行调整。这种方法不但费时费力，而且１人操作很难完成。　　如“工农—１２型”手扶拖拉机挡位板上的适位槽呈“工”字形。３挡、２挡分别在“工”字上方的左右侧；倒挡、１档分别在“工”字下方的左 Unblocking is one of the common faults of walking tractors. The conventional elimination method must be removed after the tow frame or the variable speed cover is first adjusted. This method is not only time-consuming and laborious, and one person operation is difficult to complete. Such as “worker-peasant -12” walking tractor gear plate slot is “workers” shape. 3 block, 2 block respectively in the “workers” word on the left and right side; reverse gear, a file in the “workers” below the word left