At present, the 125 displacement water-cooled Shark motorcycle is equipped with a 152MI water-cooled engine (150 displacement water-cooled car is equipped with a 157MJ engine). When the motorcycle travels tens of thousands of kilometers, the water seal mechanism of its water pump (mainly dynamic and static ring with research seal) will produce leakage phenomenon to different degrees under the influence of a variety of factors. In addition, under different road conditions, dirt, grease, dirt and other impurities on the ground of the motorcycle will slowly block the leakage hole on the lower side of the pump casing, and make the water of the cooling system gradually penetrate into the crankcase oil pool through the pump sealing device, resulting in the lubricating oil emulsification and deterioration turning to gray. For example, the oil deterioration caused by the failure of the water seal mechanism of the pump is relatively hidden, usually in the replacement of new oil after less than dozens of kilometers, lubricating oil emulsification deterioration will occur again, to motorcycle users and maintenance workers to analyze and judge the fault brings great difficulties.

First, open the cylinder cover and use the opposite dimension of 12mm hexagon socket wrench to check the tightening torque of the fastening cylinder nut (standard torque value is 25N.m). If the torque value is too low and the difference with the standard fastening torque is too large, the cylinder nut should be tightened again and the fault point should be confirmed by road test. If the tightening torque of cylinder head nut meets the standard value, it can be checked in the next step.

Push the motorcycle to a place close to the tap water, open the front mask of the vehicle, unscrew the radiator cover in the cold state of the engine, and carefully inspect the leakage hole of the pump housing with a flashlight, check whether there is dust, dirt blocking phenomenon. After confirmation, try to open the right crankcase cover and let out the oil in the crankcase. Note that the pump outlet should still be connected to the cylinder inlet joint. Find another rubber hose to connect with the tap and the water pump inlet, and turn on the tap switch slightly (the water pressure should not be greater than 0.5kg/cm2, because too much 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 seal device of the pump on the right cover assembly. If water oozes out through the clearance of the bearing, the failure of the dynamic and static ring seal device of the pump can be judged. To this, can first remove the pump impeller (thread is left-handed), the above static ring to try to take out. A special-purpose circlip pliers from right inside of the lid off Φ 26 hole with ring, and the use of copper bar into the pump shaft head knock gently, make the pump shaft and bearing from right "6000" the pump cavity, the appropriate size of the plug carefully up out of the "61901" bearing, cover from right inside take out water seal ring in the component, 12 "x 20 x5 oil seal".

Then, check the inside and outside of the pump cavity of the right cover in detail. If there are scraps or burrs left when disassembling, clean them up. Assembly, can be the first "61901" bearing load from right cover the inside of the pump cavity, a new replacement order 12 x 20 "x 5" oil seal (the seal removed after deformation, must be replaced a new parts), water pump shaft, "6000" bearings and Φ 26 hole with ring mount, with a little "609" glue in the ring are cylindrical surface, from the right cover outside the pump cavity is loaded. Note that the ceramic sealing surfaces 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 disassembled parts (when assembling the right cover, do not forget to insert the valve body connecting the lube passage and the return spring into the right end of the crankshaft), and connect the cooling system water pipe. At this point, the remaining water in the cooling water system should be all drained (tap water is hard water, long-term use will produce scale and block the small channel), add type 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 abnormalities are found, can hold straight gauge ruler (better blade feet) on cylinder head bottom plane and the plane on the cylinder, a thickness of 0.03 ~ 0.10 mm feeler is used to measure the straight rod and cylinder cover between the bottom plane and the plane on the cylinder clearance (the flatness value should be 0.03 ~ 0.05 mm), if the two parts flatness than using limit of 0.10 mm, then cooling fluid may through between the cylinder head and cylinder inside the plane into the crankcase. In this regard, the cylinder head and cylinder body can be combined with the plane on the special plate for grinding, cleaning and then testing, until the flatness is qualified. If the flatness of the parts is out of tolerance and cannot be repaired by grinding, it should be replaced.

It should be pointed out that, if the cylinder head, cylinder body combined with the plane leakage, the burst pressure of the cylinder will channelling into the engine channel, resulting in a sharp rise in the temperature of the cooling system, or even the radiator cover pressure valve burst open, please pay special attention. In addition, in the usual maintenance, it is necessary to carefully observe whether the leakage hole on the lower side of the pump casing is blocked or not, and dredge it according to the situation. If water is found dripping from the leakage hole on the lower side of the pump housing, it indicates that the water seal device of the pump has failed, and a new one should be replaced in time.

In addition to the common faults of ignition system, carburetor system, transmission system, piston, piston ring, cylinder wear, etc., the above faults of two-stroke and four-stroke engines are mainly determined by their different valve mechanism and mixture composition. (1) Fault diagnosis of four-stroke engine

A) Improper timing adjustment of valve distribution;

B) Valve clearance is improperly adjusted, too large or too small;

C) CAM wear;

D) The valve is ablated, the valve rod is bent, and the spring of the valve is weakened, causing the valve to leak;

E) The wear of the two journal of the camshaft and the shaft hole is out of tolerance. Due to the increase of the fit clearance between the shaft and the hole, the radial displacement of the camshaft occurs during rotation, resulting in the decrease of the valve opening. The ignition timing will also be affected for camshaft mounted models.

(2) Fault diagnosis of two-stroke engine

A) Crankshaft oil seal leakage;

B) Loose sealing of air intake;

C) The mixture of the two-stroke engine contains oil, and the combustion chamber, scavenging port, exhaust port and exhaust pipe are easy to accumulate carbon, which will hinder the airflow and increase the engine temperature. This should be paid special attention to the two-stroke engine.

D) Too much oil in the mixture.

2. Diagnosis of two kinds of engine noise