TM-9-2815-220-34 Direct Support Manual for AVDS-1790-2C and AVDS-1790-2D Engines Download
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sleeves in the rocker arms for scoring and loose- ness. Check bearing sleeves against limits specified in repair standards (table 3-13). Replace bearing sleeve that do not meet these limits. In- spect valve rocker arm rollers for scuff or score marks and looseness on hub. Rotate roller and check clearance between roller and hub by mount- ing rocker arm securely in a soft-jawed vise. Set a dial indicator against contact surface of roller and move roller through extremes of its travel. Check reading on the dial indicator. Limits should be I 0.0055 in. maximum. Replace rocker arms if rollers or hubs are damaged. Inspect adjusting screws (34) for stripped or damaged threads. Check screw by tuing screw in and out of rocker arms. Screw must tu freely. Check swivel pad and adjusting screw for free rotation. Mark damaged parts for replacement. (3) Valve rocker arm shafts. Check valve rocker arm shafts (14 and 31) r cracks, scuff, scores and metal pick up or plugged oil passages. Check shafts against limits specified in repair standards (table 3-13). Repair or replace unserviceable shafts (para 3-7). (4) Valves: (a) Valve head. Check intake and exhaust valves (2 and 3, fig. 3-190) for evidence of pitting, imperfect seating, cracks or warpage on valve head. Heavy discoloration, burning, erosion, or a heavy carbon deposit on valve face indicates a warped valve. A light frosted appearance or minor discoloration on valve face does not indicate a TM 9·2815-220-34 warped or unserviceable valve. (b) Valve stem. Inspect the valve stems and the locking groove in the stems for pitting, scoiing, cracks, or damaged tips. Check valves against lim- its specified in repair standards (table 3-13). Re- place valves that are warped, cracked, or unserv- iceable. NOTE Do not interpret termination of chrome plating on stem as a crack. (5) Valve springs. Inspect inner spring(lO, fig. 3-190), intet·mediate spring (9), and outer spring (8) for wear, cracks, set or other evidence of failure. Check all springs against limits specified in the repair standards (table 3-13). (6) Valtie s7n-ing 1·etainets, valve rotors, and locks. Inspect valve spring retainers (11 and 38) and intake spring seat (7) for wear and cracks. Check exhaust valve rotor (37) by rotating inner section. Inner section must rotate freely. Inspect rotor for wear or cracks. Inspect spring retainer locks for wear or cracks. Worn locks wiJJ have ridges on top face. Replace any unserviceable parts. NOTE Three different models of exhaust valve rotors, all manufactured by one manufac- turer, are optional in this cylinder assem- bly. Two of these optional rotors will ro- tate in either direction. The other optional rotor will rotate in one direction only. Change 2 3·101