TM 10-4320-344-244.4.14 PistonandConnectingRodAssemblyMaintenance,Model609-A.(Continued)Table 4-7. Piston Dimensions, Model 609-A. (Continued)DimensionMinimumMaximumWidth of ring groove-0.125 inches (3.175 mm)top-KeystonenominalWidth of ring groove -0.1210 inches (3.0734 mm)0.1270 inches (3.2258 mm)2ndWidth of ring groove -0.1830 inches (4.6482 mm)0.1890 inches (4.8006 mm)o i l c o n t r oli .Inspect crankshaft for any rough or scored marks that might damage bearings (3and 13). If any rough marks are found, polish shaft with emery cloth.Thoroughly clean shaft after polishing.All parts should be measured at room temperature; otherwise, dimensionaltolerances during piston and ring fitting may be incorrect.j .Measure size of cylinder bores.k.l .m..Piston size is identified by letter stamped on top of piston..If new standard piston is installed, make sure size letter stampedon top of piston-agrees with bore size letter stamped on cylinderb l o c k.Check fit of piston (10) without piston rings (4, 5, 6, and 7) in cylinderbore. If any binding occurs, remove piston (10) and check for burrs on piston(10) and cylinder wall.Insert new piston rings (4, 5, 6, and 7) one at a time inside cylinder bore.Ensure each piston ring (4, 5, 6, and 7) is at bottom of piston ring (4, 5, 6,and 7) travel.Using a piston (10), push piston ring (4, 5, 6, and 7) down so it is parallelwith top of cylinder bore.All ring gaps should be between 0.0100 inches (0.2540 mm) and 0.0200 inches(0.5080 mm).n.Measure gap in piston ring (4, 5, 6, and 7). After checking clearance, removepiston rings (4, 5, 6, and 7).o .Inspect piston rings (4, 5, 6, and 7) for the clearances listed in Table 4-8.4-46NOTENOTE
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