4.  Loose intake pipe flanges 5.  Loose or defective spark plug inserts 6.  External damage, such as cracks Loosen the pushrod packing gland nuts or hose clamps, top  and bottom. Pushrods are removed by depressing the rocker  arms with a special tool, or by removing the rocker arm.  Before removing the pushrods, turn the crankshaft until the  piston is at top dead center on the compression stroke. This  relieves the pressure on both intake and exhaust rocker arms.  It is also wise to back off the adjusting nut as far as possible,  because this allows maximum clearance for pushrod removal  when the rocker arms are depressed. and remove the spark plug lead clamps. Do not remove the  spark plugs until ready to pull the cylinder off. Remove the  rocker box covers. First, remove the nuts and then tap the  cover lightly with a rawhide mallet or plastic hammer. Never  pry the cover off with a screwdriver or similar tool. On some model engines, or if the engine is rotated, tappets  and springs of lower cylinders can fall out. Provision must be  made to catch them as the pushrod and housing are removed. After removing the pushrods, examine them for markings or  mark them so that they may be replaced in the same location  as they were before removal. The ball ends are usually  worn to fit the sockets in which they have been operating.  Furthermore, on some engines, pushrods are not all of the  same length. A good procedure is to mark the pushrods near  the valve tappet ends No. 1 IN, No. 1 EX, No. 2 IN, No. 2 EX.,  etc. On fuel injection engines, disconnect the fuel injection  line and any line clamps that interfere with cylinder removal. The next step in removing the cylinder is to cut the lock wire  or remove the cotter pin, and pry off the locking device from  the cylinder-attaching cap-screws or nuts. Remove all the  screws or nuts except two located 180° apart. Use the wrench  specified for this purpose in the special tools section of the  applicable manual. Finally, while supporting the cylinder, remove the two  remaining nuts and gently pull the cylinder away from the  crankcase. Two technicians working together during this  step, as well as during the remaining procedure for cylinder  replacement, helps prevent damage or dropping of the  cylinder. After the cylinder skirt has cleared the crankcase,  but before the piston protrudes from the skirt, provide some  means (usually a shop cloth) for preventing pieces of broken  rings from falling into the crankcase. After the piston has  been removed, remove the cloths and carefully check that  all pieces were prevented from falling into the crankcase. Place a support on the cylinder mounting pad and secure it  with two cap-screws or nuts. Then, remove the piston and  ring assembly from the connecting rod. A pin pusher or puller  tool can be used when varnish makes it hard to remove the  pin. If the special tool is not available and a drift is used to  Assuming that all obstructing cowling and brackets have  been removed, first remove the intake pipe and exhaust pipes.  Plug or cover openings in the intake or diffuser section. Then,  remove cylinder deflectors and any attaching brackets that  would obstruct cylinder removal. Loosen the spark plugs  Since these instructions are meant to cover all air-cooled  engines, they are of a very general nature. The applicable  manufacturer’s maintenance manual should be consulted for  torque values and special precautions applying to a particular  aircraft and engine. However, always practice neatness  and cleanliness, and always protect openings so that nuts,  washers, tools, and miscellaneous items do not enter the  engine’s internal sections.  Correct procedures and care are important when replacing  cylinders. Careless work or the use of incorrect tools can  damage the replacement cylinder or its parts. Incorrect  procedures in installing rocker-box covers may result in  troublesome oil leaks. Improper torque on cylinder hold down  nuts or cap-screws can easily result in a cylinder malfunction  and subsequent engine failure. When installing a chrome-plated cylinder, do not use  chrome-plated piston rings. The matched assembly includes  the correct piston rings. However, if a piston ring is broken  during cylinder installation, check the cylinder marking to  determine what ring, chrome-plated or otherwise, is correct  for replacement. Similar precautions must be taken to be sure  that the correct size rings are installed. Normally, all the cylinders in an engine are similar, all are  standard size or all a certain oversize, and all are steel bore or  all are chrome-plated. The size of the cylinder is indicated by  a color code around the barrel between the attaching flange  and the lower barrel cooling fin. In some instances, air-cooled  engines are equipped with chrome-plated cylinders. Chrome- plated cylinders are usually identified by a paint band around  the barrel between the attaching flange and the lower barrel  cooling fin. This color band is usually international orange.  The cylinder is always replaced as a complete assembly,  which includes piston, rings, valves, and valve springs.  Obtain the cylinder by ordering the cylinder assembly under  the part number specified in the engine parts catalog. Parts,  such as valve springs, rocker arms, and rocker box covers,  may be replaced individually. Cylinder Removal 10-42