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What is the reason of the engine link breakage?

Date: 2017-05-22   Page view: 1078

What is the reason of the engine link breakage?

 

Small engine suddenly issued a "bang" sound in the work, and then automatically shut down.When starting again,Found that no compression .

Open the crankcase cover to see: the connecting rod is broken.

 

In the face of a small engine engine breakage, we often have a lot of doubts. How could this happen? What is the cause of the break?

 

A lot of research and maintenance experience shows that we can find the answer to the problem by looking at the fracture of the connecting rod and the state of the engine after the break.

 

phenomenon 1: connecting rod small head end, the piston stopped at the top dead center position


When it is found that the connecting rod is broken and the piston is stopped near the top dead center, it is stated that the breakage is caused by overspeed

 

In the case of overspeed, the connecting rod is often broken at the weakest part (ie about 2.5 cm from the piston pin). Usually we will see the connecting rod broken into many sections. Speed crank and speed gear can also help us make speeding judgments: such as the speed of the crank clamping bolt is loose, speed gear is off or damaged.

The design speed of a small four-stroke general engine is no more than 4000 rpm. At 4000 rpm, the load on the engine components is within acceptable limits. These loads increase significantly when the engine is overspeed. Each time the speed increases by 500 rpm, the force at both ends of the connecting rod will increase by 44%.

 

Do not arbitrarily increase the speed of the engine


1.each engine before leaving the factory,have set the maximum speed.

2.can not arbitrarily increase the maximum speed of the engine.

3.if you find the engine speed (measured by the tachometer, or hear screams), should immediately let the engine flame and sent to the dealer to check, re-adjust the speed.

 

phenomenon 2: Connecting rod bulkhead breakage,and the connecting rod and crankshaft joints have obvious metal transfer scratches

 

This situation shows that poor lubrication is the main cause of the engine link breakage. And poor lubrication is mainly due to lack of oil or not on time to replace the clean oil caused

 

The small engine runs fast and has an internal temperature of 400 ° C to 600 ° C. In such a bad condition, there must be a qualified oil in the aluminum link and crankshaft joint surface to form an oil film (for its cooling and lubrication), in order to prevent the prevention of metal transfer.

Otherwise, the failure of the oil or hydraulic oil caused by the joint surface dry friction will make the junction surface temperature is extremely high, resulting in metal transfer, eventually leading to the rod head fracture.


How to prevent poor engine lubrication?


1.Regular inspection of the oil level, when the oil shortage, the amount of additional oil, to prevent the engine oil shortage work.

2.Also, replace the engine oil regularly: Replace the oil every 50 hours. Long-term use of oil has lost its lubrication. Should be fully released and add new oil (Note: 10W-40 SJ grade oil can be used in most of the temperature).

3.In order to prevent large abrasives from entering the engine, the air filter should also be checked and replaced regularly

4.In short, the engine state after the breakage of the rod can tell us why the break is broken. Poor lubrication and speeding are the most common causes. Other possible causes are: connecting rod bolts loose will lead to breakage.

5.For the engine users, usually on time to maintain the engine and not tamper with the maximum engine speed, to prevent damage to the engine has important significance.