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Piston Rings, Remove and Install
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 Remove
Remove piston with con-rod – see operation "Piston with
Con-rod, Remove and Install".
 Clean
Remove piston rings with piston ring pliers (1).
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Inspect
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Piston ring grooves – use ground-down side of old piston
ring. Check piston ring gap with feeler gauge by inserting piston
ring at narrowest point of the cylinder bore.
Permissible ring gap:
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I
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Rectangular compression ring
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0.20 to 0.45 mm
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(first compression ring, DTL engines up to engine number
17B58981)
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Double trapezoidal ring
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0.25 to 0.50 mm
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(first compression ring, DTL engines as of engine number
17B58982, DTH and DTR engines)
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II
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Tapered compression ring (second compression ring)
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0.25 to 0.50 mm
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III
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Outer bevel ring (oil scraper ring)
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0.25 to 0.50 mm
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Check piston ring vertical play with feeler gauge in piston ring
groove.
Permissible vertical play:
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I
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Rectangular compression ring
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0.01 to 0.03 mm.
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(first compression ring, DTL engines up to engine number
17B58981)
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Double trapezoidal ring
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0.08 to 0.12 mm
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(first compression ring, DTL engines as of engine number
17B58982, DTH and DTR engines)
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II
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Tapered compression ring (second compression ring)
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0.01 to 0.03 mm.
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III
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Outer bevel ring (oil scraper ring)
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0.01 to 0.03 mm.
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Install
Insert piston rings in piston with piston ring pliers.
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Insert tapered compression ring (II) in piston with mark "TOP"
on top.
Adjust position of piston ring gaps – the gap of each
piston ring must be offset by 120° cylinder bore.
Install piston with con-rod – see operation "Piston with
Con-rod, Remove and Install".
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