一台东方红-75型拖拉机因三缸连杆螺栓折断造成捣缸事故。修复并起动着火后,发生发动机严重冒黑烟的故障,用断缸法检查发现黑烟主要来自三缸。检查了三缸的喷油器、气门间隙、喷油泵以及进、排气通道后,未发现问题。无奈中偶然发现在用手摇把摇转发动机的过程中,三缸气门间隙在某个位置时有不正常增大的现象。于是重新用气门间隙“两次检查调整法”(即一次调4个气门,两次调完)复查,其结果是各气门问隙均调整无误,气门问隙 A Dongfanghong -75 tractor torn off due to three-cylinder connecting rod bolt accident. Repair and start the fire, the occurrence of serious black smoke engine failure, broken cylinder method found that black smoke mainly from the three-cylinder. Check the three-cylinder injectors, valve clearance, fuel injection and intake and exhaust channels, no problems were found. Helpless to accidentally found in the process of shaking the engine with a hand crank, the three-cylinder valve clearance in a position when there is an abnormal increase in the phenomenon. So re-use the valve clearance “twice check the adjustment method ” (that is, a transfer of four valves, twice completed) review, the result is the valve clearance are adjusted, valve clearance