TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download
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6-26. Repair a. Pistons. (1) Replace pistons which are not within limits specified in overhaul standards (table 6- 13). (2) Replace pistons which are distorted, cracked, worn, or abraded. (3) Replace piston if oil holes in the ring lands cannot be cleared or if lands are damaged or broken. (4) Replace pistons that are badly burred, nicked, or scratched. Remove minor burs, nicks, or scratches from pistons with crocus cloth dipped in dry-cleaning solvent or mineral spirits paint thinner. b. Piston Rings. Piston rings cannot be repaired. All piston rings must be replaced with new rings at engine overhaul. c. Piston Pins and Plugs. Replace piston pins and plugs which are cracked, or have deep nicks or scratches. Remove minor nicks or scratches with crocus cloth dipped in dry-cleaning solvent or mineral spirits paint thinner. Replace piston pin plugs which have a large wear pattern on the end. Replace piston pins and plugs not within limits specified in overhaul standards (table 6- 13). 6-27. Assembly a. Check marking on new rings and install the upper (tapered) compression ring and the two intermediate compression rings with the marking “UP” toward the piston dome. Install all rings using remover and replacer - 5120-795-0177 as shown in figures 6-44 and 6-45. Use care in installing rings to avoid damaging ring lands or distorting rings. b. Measure side clearance of all new ring (fig. 6-46). Replace rings when side clearance does not conform to limits specified in overhaul standards (table 6-13). Figure 6-46. Checking piston ring side clearance. c. Install piston in bore of piston and install a piston pin plug at each end of piston pin. d. Select pistons according to weight. Variations in the weight of pistons in an engine should not exceed 0.5 ounce. 6-50