The purpose of a piston ring is to provide a tight seal between the piston and the cylinder wall, creating a seal for compression, and keeping oil out of combustion chamber. When these rings become worn, engine oil can get past the rings, enter the combustion chamber, and create black smoke. When this occurs, you will need to replace the piston rings. A compression test can also indicate bad rings. If the cylinder is reading low, you should inject some oil, which will fill the gap between the rings and the cylinder wall. Now, do a second compression test. If the pressure has increased, it indicates worn rings. After you have determined the rings are bad, you will need to replace them. You can begin this repair by draining all fluids and removing the air filter and air filter housing. Next, remove the spark plug wire and spark plug, the...
The purpose of a piston ring is to provide a tight seal between the piston and the cylinder wall, creating a seal for compression, and keeping oil out of combustion chamber. When these rings become worn, engine oil can get past the rings, enter the combustion chamber, and create black smoke. When this occurs, you will need to replace the piston rings. A compression test can also indicate bad rings. If the cylinder is reading low, you should inject some oil, which will fill the gap between the rings and the cylinder wall. Now, do a second compression test. If the pressure has increased, it indicates worn rings. After you have determined the rings are bad, you will need to replace them. You can begin this repair by draining all fluids and removing the air filter and air filter housing. Next, remove the spark plug wire and spark plug, the exhaust manifold or muffler from the cylinder head, and the carburetor from the cylinder head. Now, pull the valve cover off with the gasket. Rotate the piston to the bottom, remove the rocker arm nuts and remove the push rods. Next, remove all the bolts holding the cylinder head to the engine block in an alternating pattern (to prevent warping the cylinder head) and remove the head. Next, pull off the old head gasket. Clean the surfaces of the engine block and cylinder head with a soft cloth. Next remove the crank case bolts, and wiggle it off, or tap it off lightly with a hammer. There may even be a key way on the crankshaft that will have to be removed, depending on your model. Remove the camshaft by simply pulling it out. Remove the camshaft tappets, connecting rod bolts and the bottom part of the rod bearing, and rotate the crankshaft to the top. Then, reach in and push the piston out with your fingers. Now you can remove the old piston rings. Clean all the parts you are going to reuse with parts cleaner and dry them thoroughly. Install new rings onto piston, positioning the ring gaps a 1/3 interval around the ring to prevent blow by (make sure the oil ring is on the bottom). Use a piston ring installer to line everything up, then gently tap the piston into the cylinder. Be sure to lubricate the cylinder with fresh motor oil beforehand. With the piston at top dead center and contacting the crankshaft, rotate together by pushing down on the piston so you can reattach to the connecting rod bearing. They only go in one way. Lubricate the camshaft tappets and reinstall, next install the camshaft by making sure the timing marks are in line. Be sure to lubricate all moving parts with motor oil or white grease before you install them. Next, re-install the crank cover with a new gasket. Then, re-install the cylinder head with a new gasket, and torque down in an alternating pattern to manufacturer specifications to prevent warping the cylinder head. Re-install the push rods, rotate the rocker arms back into place, and hand tighten the pivots. Set the gap between the rocker arms and valves from 3 to 5 thousandths of an inch, then tighten down the jam nuts to secure. Re-install the valve cover with a new gasket in an alternating pattern to manufacturer specifications to prevent warping. Install a new spark plug with the gap set to manufacturer specifications. Finally, re-attach the carburetor, air filter housing (with filter), and muffler back to the cylinder head.
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