Signs Indicating that your 4 Stroke Engine Needs Replacement

Engines blowing up in the motorsport field is a norm. Regardless of how dangerous it is, it’s inevitable, especially if you have a dated engine or one that needs servicing. And although it might not have happened to you yet, knowing when to change your engine to avoid this catastrophe is essential.

There is a myriad of signs that indicate a need for an engine change. Some are primary and often show earlier, while others are secondary and usually show late or even a few minutes before it combusts. The guide below will discuss in detail the basic signs that indicate the need for an engine change. Like, for example, how under normal circumstances, the inability to start does not indicate that your 125cc four-stroke engine is about to blow.

Read on to verse yourself with these signs and more.

Low Compression

Lack of compression often correlates with startability. This poor startability stems from valves or pistons not seating properly. When valves and pistons don’t seat properly, the engine fails to build a proper compression. This bad compression often lets the engine struggle to pick up when kickstarted.

To solve this problem, you can push the machine or use the electric start. If you feel less resistance when kickstarting, then the valves are too tight from wear. You can solve this via a valve adjustment.


If your engine tends to start with no problems whenever you use the electric start but struggles whenever kickstarted, then your machine has startability issues. As previously mentioned, poor startability does not mean your 125cc 4 stroke engine is about to blow. In such scenarios, the problem is often with the carburetion, injection, or something’s wrong in the cylinder head.

Either way, if coupled with low compression, then you need to check on what’s amiss and fix it before it worsens.

Excessive Coolant

Coolant exiting the overflow tube is necessary whenever the bike overheats or gets tipped over. However, it should not occur regularly. Excessive coolant exiting the overflow tube indicates that something is amiss.

If you notice such a case with your bike, then that’s a good indicator of a leaking gasket.

Coolant Seepage

Coolant seepage is an indication of a faulty water pump seal. If such an issue stays without any repair, then the entire cooling system will eventually empty. An empty system ultimately leads to overheating, which further leads to huge damages on your bike.

Crankcase Breather

Many engines, including the 125cc 4 stroke engine, have the crankcase breather vented to the airbox. When a large amount of oil blows out of the breather or oil accumulates in the airbox when you rev the engine is something worth a look at.

Higher than normal pressures in the crankcase are the cause of oil blowing out the breather. Such a case often stems from poor sealing that allows combustion pressure into the crankcase.

Fix the piston rings by ensuring the sealing is tight to avoid high pressure.

Engine Oil

To know what’s happening in your 125cc four-stroke engine, ensure you check the engine oil composition. Check the color of the oil and keenly check what the oil composition is. If it’s milky, then that’s an indicator that there’s a leak that allows moisture in. On the other hand, black oil is an indication of poor maintenance; all you need is an oil change.

Often check your engine oil, you might run a quick diagnosis of your engine through checking it’s oil.

Machine engines are vital for efficient performance. Therefore, they ought to be in good condition for the best results. The signs above will help in the maintenance of your 125cc four-stroke engine. If you need to change, consult credible companies such as Coolster to offer you the best service.

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