ENGINE 88 Fig. 6 Fig. 7 Fig. 8 PISTONS AND CONNECTING RODS REMOVAL (Cylinder head and oil sump removed) 1 Carefully remove combustion residues from top end of cylinder bores, preferably by a broken piston ring. Cut ridge by ridge cutter. 2 Turn crankshaft and bring a pair of pistons to bottom most position. Unscrew their connecting rod cap mounting bolts Fig. 6 and remove caps with bearing shell. Turn crankshaft to bring this pair of pistons and connecting rod to top most position. Push these piston assemblies-out of bores one by one using mallet wooden handle. Remove remaining pistons in same manner. NOTE : Keep connecting rods and caps in sets. Preferably assembleconnectingrodsandtheir capsafter removal so that chances ofmixing/damageareavoided. Verify serial numbers on cap and connecting rod. 3 Remove piston pin circlips with a suitable plier Fig. 7. 4 Remove piston pins with drift, 312 58913 39 (it is advisable todippiston inhot oil at 70degC to 80deg C before forcing piston pin out, if pistons are to be reused). 5 Keep piston and piston pins in sets. 6 Remove connecting rod bearing shell and dulymark them in case these are to be reused. SELECTION OF PISTONS AND REPLACEMENT OF PISTON RINGS 1 Remove piston rings from piston using piston ring expander Fig. 8. 2 Remove carbon deposit and clean pistons/rings thoroughly. 3 In case cylinder bore taper and ovality is within specified limit, same piston/rings may be reused. However, piston and rings should be examined thoroughly for following: a. Piston - Cracks, scoring, other damages, ring groove wear,wear of piston pin bore in piston,circlip groove wear/damage. b. Piston rings - Scoring, lateral clearance in piston ring grooves Fig. 9 and butt clearance (ring gap) in cylinder bore Fig. 10 (this is to be checked in unworn portion of the cylinder bore). c. Piston or rings with any of the above referred defects should be replaced.
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