Excessive wear and tear of motorcycle camshafts occurs repeatedly, see how the master can find out the real culprit

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Author: Ruan Tianlin

A CL125-2 Chunlan Leopard motorcycle drove more than 80,000 kilometers, and the cylinder head appeared The abnormal sound was confirmed to be caused by the camshaft wear after inspection. After replacing the new camshaft, the ride was less than 3,000 kilometers, the failure reappeared, and the cause of the failure is unknown.

The maintenance staff asked about the specific conditions of the user’s vehicle and learned that they were traveling some time ago and did not check and add engine oil in time due to rushing on the way. As a result, the cylinder was pulled. The friction pair parts such as pistons, piston rings, cylinders, etc. are seriously worn out.

At that time, the engine was disassembled in a nearby repair shop, and pistons and cylinders were replaced. At that time, no problems were found in the test drive, and I kept riding normally. .

But after driving more than 300 kilometers, I feel that the engine sound is wrong, and there is an unpleasant 'click' sound from the cylinder head. Find a repair station and check it carefully. Look for the abnormal noise and open the cylinder head cover to find that the journal and bushing at the right end of the camshaft have been severely worn.

This situation is mostly caused by the blockage of the oil filter, which leads to poor oil circulation. The maintenance personnel opened the right crankcase cover and maintained and cleaned the oil pump filter. And replace the new camshaft and bushings, install and deliver to the vehicle.

But after running less than 200 kilometers, the abnormal noise of the cylinder head appeared again. After disassembling the engine again, it was found that it was exactly the same as the last time, but the camshaft's right end journal and bushing were severely worn. It seems that the last inspection was incomplete and the real source of the failure was not found.

The maintenance personnel analyze this kind of recurring abnormal wear failure, which should be related to the lack of oil lubrication factor.

According to the wear part, it may be caused by blockage of the right side of the engine. Unscrew the oil dipstick on the right crankcase cover, and use a condensing flashlight to check whether the oil passage at the right end of the crankshaft is equipped with a return spring and a valve body. The check result is normal.

Open the right crankcase cover again and carefully observe the casting oil passage hole on the upper side of the right crankcase. No abnormality was found. The oil passage in the right crankcase cover is also unblocked, indicating that there is no blockage of the oil passage here. To completely eliminate the fault, the only way to resolve the engine is to find the root cause of the fault.

Remove the cylinder head, cylinder block, piston and other components in order. When inspecting the oil passage on the upper plane of the right crankcase, it was found that at the junction of an M8×190mm cylinder head bolt on the right and the M8 threaded hole on the crankcase, more sealant adhered to the Φ9mm hole and the M8 bolt. Around the roots.

Even through visual observation, it was found that a large part of the oil passage here was covered. It seems that when the cylinder was replaced, the sealant was applied too much. , Blocking the oil passage, causing the oil passage dedicated to the right end of the camshaft to be partially blocked, and abnormal wear of the camshaft due to poor lubrication.

Carefully remove excess sealant, remove old gaskets on the plane, replace damaged parts, and reinstall the engine. Start the vehicle without installing the cylinder head cover.

It was confirmed that the oil circuit at the right end of the cylinder head camshaft returned to normal, and the cylinder head cover was installed. After warming up the car and driving on the road, everything returned to normal, the abnormal noise in the cylinder head disappeared, and it was given to users to ride.

More than three months later, I visited the user on the phone and learned that the vehicle had been riding for nearly a thousand miles, and the abnormal sound of the cylinder head did not appear. Confirm that the fault has been eliminated.

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