购买20马力以下的手扶拖拉机和四轮拖拉机时，要注意以下几点：一、外对。机件是否完整，连接部位是否牢固，有无漏油、漏水、漏气现象。二、性能。以每分钟80转的速度手摇机柄，并逐渐加快，不超过三次应能启动。三、运转。机油压力指示阔的浮标应升起，发动机工作平稳，无异 Buy 20 horsepower following the tractor and four-wheel tractor, pay attention to the following points: First, external. Whether the parts are intact, whether the connecting parts are firm, whether there is oil leakage, water leakage or air leakage. Second, the performance. 80 rpm hand crank speed, and gradually speed up, no more than three times should be able to start. Third, operation. The buoy with wide oil pressure indication should rise, the engine works smoothly, no different