POWERHEAD - 4-2390-817643R1 DECEMBER 1996
CLEANING PISTON RING GROOVES
IMPORTANT: The piston rings are half – keystone rings
– (tapered on the top side) – follow cleaning and in-
spection carefully! Chromed ring is installed on top.
Enlarged View of
Piston Ring Grooves
!
CAUTION
Care must be taken not to scratch the side surfaces of
ring groove. Scratching the side surfaces of the ring
groove will cause damage to the ring groove.
• Use a bristle brush and carbon remover solution to re-
move carbon from side surfaces.
• A tool can be made for cleaning the inner diameter of
the tapered ring grooves. The tool can be made from a
broken tapered piston ring with the side taper removed
to enable inside edge of the ring to reach the inside di-
ameter of the groove. Carefully scrape the carbon from
inner diameter of ring grooves. Care must be taken not
to damage the grooves by scratching the surfaces of
the grooves.
MEASURING PISTON SKIRT
Measure piston skirt at right angle (90°) to piston pin cent-
erline, 0.50 in. (12.7 mm) up from bottom edge of skirt.
.50 in.
(12.7 mm)
PISTON PISTON SKIRT CYL. BORE
SIZE DIAMETER FINISH HONE
Standard 2.950 in. 2.955 in.
Piston (74.93 mm) (75.057 mm)
.015 2.965 in. 2.970 in.
Oversize (75.31 mm) (75.438 mm)
.030 2.980 in. 2.985 in.
Oversize (75.69 mm) (75.819 mm)
Crankshaft
• Inspect crankshaft to drive shaft splines for wear. (Re-
place crankshaft, if necessary.)
• Check crankshaft for straightness. (Replace as neces-
sary.)
• Inspect crankshaft oil seal surfaces. Sealing surfaces
must not be grooved, pitted or scratched. (Replace as
necessary.)
• Check all crankshaft bearing surfaces for rust, water
marks, chatter marks, uneven wear and/or overheat-
ing. (Refer to “Connecting Rods”.)
• If necessary, clean crankshaft surfaces with crocus
cloth as shown.
PE-51089
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