1. Connecting rod bolt bears great alternating impact load during engine operation. It is an important part of small mixer engine. It is made of high-quality alloy steel through quenching and tempering treatment and precision machining. It has high strength and impact toughness. It can not be replaced by ordinary bolts or low-quality parts. If the bolt material, heat treatment and machining accuracy do not meet the technical requirements, it will lead to insufficient mechanical strength and deformation and fracture accidents.

2、裝配前應仔細檢查。當發現螺栓上有劃傷、滑扣、裂口、凹痕、縮頸或裂紋(應用浸油法檢查或磁力探傷檢查)，或螺栓、螺母配合松弛，或螺栓不能與螺栓孔緊密配合，或利用對比法觀察，螺栓長度比新的標準螺栓長度長2%的，都應予更換。

2. Check carefully before assembly. If the bolt is found to be scratched, buckled, cracked, dented, necked or cracked (inspected by oil immersion method or magnetic flaw detection), or the bolt and nut fit is loose, or the bolt cannot fit closely with the bolt hole, or the bolt length is 2% longer than the new standard bolt length by comparison method, it shall be replaced.

3、檢查連桿軸承與連桿軸頸的配合間隙，若間隙過大，易于導致連桿螺栓的斷裂事故。此時應更換新的連桿軸承或加大軸承，并予選配或刮配。

3. Check the fit clearance between connecting rod bearing and connecting rod journal. If the clearance is too large, it is easy to cause the fracture accident of connecting rod bolt. At this time, the connecting rod bearing shall be replaced with a new one or enlarged one, and shall be selected or scraped.

4、檢查連桿螺栓或螺母與連桿端蓋臺肩支承面的貼合情況，若有毛刺或不平，應予修磨，否則連桿螺栓受附加力矩作用，極易折斷。

4. Check the fit between the connecting rod bolt or nut and the shoulder bearing surface of the connecting rod end cap. If there is burr or unevenness, it shall be polished, otherwise the connecting rod bolt is easy to break under the action of additional torque.

5、裝配時應用扭力扳手將連桿螺栓交替分次(一般分3—4次)逐步均勻擰至規定鈕矩。若擰緊鈕矩不足，工作中連桿結合面產生縫隙，螺栓受沖擊力時易被拉斷或剪斷；擰得過緊，螺栓伸長變形，強度降低，受力后易折斷損壞。各種機型發動機的連桿螺栓規定扭矩不盡相同，在缺乏技術資料的情況下，可根據螺栓直徑估算其安全權矩范圍，如MU連桿螺栓，其安全扭矩為60—80Nm；M12螺栓，其扭矩為80—100Nm；M14螺栓，其扭矩為100—120Nmo。

5. During assembly, the connecting rod bolts shall be tightened to the specified torque with a torque wrench in alternating times (generally 3-4 times). If the tightening button torque is insufficient, there is a gap on the connecting rod joint surface during operation, and the bolt is easy to be pulled or cut off when subjected to impact force; If it is tightened too tightly, the bolt will stretch and deform, the strength will be reduced, and it is easy to break and damage after being stressed. The specified torque of connecting rod bolts of various engines is different. In the absence of technical data, the safety torque range can be estimated according to the bolt diameter. For example, the safety torque of Mu connecting rod bolt is 60-80nm; M12 bolt, with torque of 80-100nm; M14 bolt with torque of 100-120nmo.

6、打螺栓時若發現同一連桿上某一螺栓扭矩超過規定值過多時，應將該連桿上的兩只連桿螺栓全部擰松后重新分次交替擰緊，并使兩只螺栓松緊一致。不允許僅僅松退擰得過緊的那只螺栓，否則螺栓產生附加彎曲應力，易疲勞斷裂。

6. If it is found that the torque of a bolt on the same connecting rod exceeds the specified value too much during bolt driving, loosen all the two connecting rod bolts on the connecting rod and tighten them alternately in several times, and make the tightness of the two bolts consistent. It is not allowed to only loosen the over tightened bolt, otherwise the bolt will produce additional bending stress and be prone to fatigue fracture.

7、在擰緊連桿螺栓過程中，應設法轉動曲軸，檢查其轉動是否自如，若螺栓擰緊后曲軸轉動困難應查找原因，切不可將連桿螺栓擰松來轉動曲軸。

7. During tightening the connecting rod bolts, try to rotate the crankshaft to check whether it rotates freely. If it is difficult for the crankshaft to rotate after the bolts are tightened, find out the reason. Do not loosen the connecting rod bolts to rotate the crankshaft.

8、為預防小型攪拌車連桿螺栓或螺母工作中松動，應采用嶄新的開口銷、鐵絲或鎖片等防松裝置鎖緊；若螺母上的槽口與螺栓上的孔末對正，原則上只能往里旋去對準；用過的開口銷、鐵絲或鎖片不得再用。

8. In order to prevent the connecting rod bolts or nuts of small mixer from loosening during operation, new locking devices such as cotter pin, iron wire or locking plate shall be used for locking; If the notch on the nut is aligned with the end of the hole on the bolt, in principle, it can only be screwed inward for alignment; Used cotter pins, wires or locking tabs shall not be reused.

9、使用中應定期檢查連桿螺栓緊臥情況，發現松退時應查找原因，檢查螺栓有無損傷，再用權力扳手按規定鈕矩分次擰至規定值。

9. During use, the tightening and lying of connecting rod bolts shall be checked regularly. When it is found that the connecting rod bolts are loosened, the cause shall be found, the bolts shall be checked for damage, and then the power wrench shall be used to screw them to the specified value according to the specified button torque.

10、工作中當連桿螺栓松退或被拉長時，在完全松脫、斷裂之前，因連桿軸承松曠，會發出較大的敲擊聲和振動，此時應立即停車，以免發生更大事故。

10. During operation, when the connecting rod bolt is loosened or stretched, before it is completely loosened and broken, there will be a large knocking sound and vibration due to the looseness of the connecting rod bearing. At this time, stop immediately to avoid greater accidents.

11、當某根連桿螺栓有滑扣、裂損或斷裂時，應將同一連桿上的兩根連桿螺栓成對更換，不得新舊搭配使用。

11. When a connecting rod bolt is buckled, cracked or broken, the two connecting rod bolts on the same connecting rod shall be replaced in pairs, and the old and new shall not be used together.

12、當發動機多次燒瓦或一次燒瓦嚴重時，連桿螺栓材料受高溫退火作用，金相組織發生變化，機械強度下降，承載能力下降，應予換新。

12. When the engine burns the Bush for many times or once, the connecting rod bolt material is subject to high-temperature annealing, the metallographic structure changes, the mechanical strength decreases and the bearing capacity decreases, so it should be replaced.

13、當發動機出現飛車、咬缸或翻車事故后，切不可忽視對連桿螺栓的仔細檢查，當發現螺栓變形、裂損后，應及時更換。

13. In case of flying, cylinder biting or rollover accidents of the engine, the careful inspection of the connecting rod bolts must not be ignored. When the bolts are found to be deformed and cracked, they should be replaced in time.

14、為預防連桿螺栓疲勞斷裂損壞，在小型攪拌車發動機工作累計6000—7000小時后，即使螺栓外表元明顯損傷，也應換新。

14. In order to prevent fatigue fracture and damage of connecting rod bolts, even if the bolt surface is obviously damaged after 6000-7000 hours of operation of small mixer engine, it shall be replaced.