At present the domestic 125 displacement water cooled shark motorcycle are equipped with water cooled 152MI engine (150 displacement water cooled car is equipped with 157MJ engine), when the motorcycle driving tens of thousands of kilometers, the water pump sealing mechanism (mainly dynamic, static ring with seal) will produce different degrees of leakage phenomenon under the influence of a variety of factors. Coupled with the motorcycle running in different road conditions, the ground dust, oil, dirt and other impurities will slowly block the leakage hole under the water pump shell, so that the cooling system through the water pump sealing device gradually into the crankcase oil pool, resulting in lubricating oil emulsion deterioration is gray. As the failure of the water pump sealing mechanism caused by oil deterioration fault is hidden, usually in the replacement of new oil after less than dozens of kilometers, lubricating oil emulsion deterioration fault will appear, to motorcycle users and maintenance workers analysis, judgment of the fault brings great difficulties.

Firstly, open the cylinder cover and check the tightening torque of the cylinder head nut (the standard torque value is 25N.m) using a hexagonal socket wrench with the opposite side size of 12mm. If the torque value is too low and too large to the standard tightening torque, the cylinder head nut should be tightened again and the fault point should be confirmed by road test. If the tightening torque of the cylinder head nut meets the standard value, the next check can be made.

Push the motorcycle to a place close to the tap water, open the front mask of the vehicle, unscrew the radiator cover under the cold condition of the engine, and carefully inspect and check whether the leakage hole of the pump shell is blocked by dust and dirt with the flashlight. After confirmation, you can try to open the cover of the right crankcase and release the oil in the crankcase. Note that the water pump outlet should still be connected with the inlet pipe joint of the cylinder body. Find another rubber water pipe respectively connected with the tap and the pump inlet, slightly open the tap switch (water pressure should not be greater than 0.5kg/cm2, because high water pressure will make the water seal device open earlier), as long as the tap water can flow in the cooling system. Keep the water flowing for about 3 minutes, carefully observe the water pump sealing device on the right cover assembly, if there is water leakage through the bearing void, you can judge the failure of the dynamic and static ring sealing device of the pump. In this regard, the pump impeller can be first removed (the thread is left), the above static ring to try to take out. Use the special retainer pliers to remove the retainer ring with φ26 hole from the inside of the right cover, use the copper rod to touch the pump shaft head and gently knock, make the pump shaft and "6000" bearing out of the pump chamber of the right cover, carefully pull out the "61901" bearing with the mandrel of appropriate size, and take out the moving ring and "12×20×5" oil seal in the water seal assembly from the inside of the right cover.

Then, check the right cover pump cavity in detail around the body, if there is debris or burr left when disassembly, should be cleaned up. When assembling, load the "61901" bearing from the pump cavity inside the right cover first, then install the newly replaced "12×20×5" oil seal (the oil seal has been deformed after disassembly, and must be replaced with a new piece), pump shaft, "6000" bearing and φ26 hole with a retaining ring, and stick a little "609" fixing glue on the outer circular surface of the moving ring. Load from the pump cavity on the outside of the right cover. Note that the two ceramic sealing planes of the moving and static rings should be kept clean, screw on the pump impeller, and tighten the torque to 12N.m. Finally reassemble the removed parts (when assembling the right cover, don't forget to insert the valve body and return spring connecting the lubricating oil channel into the right end of the crankshaft), and connect the cooling water pipe. At this time, the rest of the tap water in the cooling system should be drained (tap water is hard water, long-term use will produce scale and block small waterways), add the selection of antifreeze, exhaust the air in the cooling system before starting.

If you use a water pressure test method, any leakage phenomenon, and found no water pump water seal device is connected to the pump must be rubber hose managed to release and let go the cooling fluid inside the engine water jacket, remove the cylinder cover parts check cylinder gasket, studying the fluorine rubber on either side of the cylinder pad with and without deformation and falls off phenomenon, and as to replace. If no abnormality is found, you can hold the straight ruler (a knife edge ruler is better) against the bottom plane of the cylinder cover and the upper plane of the cylinder body, and use the thickness of 0.03-0.10mm feeler piece to measure the gap between the straight ruler and the bottom plane of the cylinder cover and the upper plane of the cylinder body (the flatness value should be 0.03-0.05mm). If the flatness of the two parts exceeds the service limit of 0.10mm, it indicates that the coolant may seep into the crankcase through the plane between the cylinder head and the cylinder body. In this regard, the cylinder head and cylinder body combined plane can be respectively ground on a special plate, and then tested after cleaning until the flatness is qualified. If the flatness of the machine is too poor to be repaired by grinding, it should be replaced.

It should be pointed out that if the cylinder head, cylinder body combined with the plane of serious leakage, the cylinder pressure will be channeled into the engine channel, resulting in a sharp rise in the water temperature in the cooling system, and even the radiator cover pressure valve opened, please pay special attention. In addition, in the usual maintenance, it is necessary to carefully observe the leakage hole under the pump shell whether there is blockage phenomenon, and according to the situation dredge it. If water drops from the leakage hole on the lower side of the water pump shell, it indicates that the water pump sealing device of the machine has failed, and a new one should be replaced in time.

Engine power shortage, starting difficulties, fuel consumption increase in addition to the ignition system, carburetor system, transmission system, piston, piston ring, cylinder wear and other common faults, two stroke and four stroke engine mainly because of their valve mechanism and mixture composition is different. (1) Fault diagnosis of four-stroke engine

A) Improper adjustment of valve timing;

B) Improper valve clearance adjustment, too large or too small;

C) CAM wear;

D) Valve ablation, valve rod bending, valve spring elasticity is weakened, so that the valve leakage;

E) The wear of camshaft neck and shaft hole is out of tolerance. Due to the increase of the clearance between shaft and hole, the camshaft produces radial displacement in rotation, resulting in the decrease of valve opening. Ignition timing will also be affected for models with interrupters mounted on camshafts.

(2) Fault diagnosis of two-stroke engine

A) crankshaft oil seal leakage;

B) The air inlet is not tightly closed;

C) The mixture of two-stroke engine contains oil, combustion chamber, scour, exhaust port and exhaust pipe are easy to accumulate carbon, so that the air flow is blocked and the engine temperature is increased, which should be paid special attention to for two-stroke engine.

D) Too much oil in the mixture.

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