Powerhead
Page 4A-40 90-8M0050731 MAY 2011
4. Localize the stroking in the smallest diameter until the drill speed is constant throughout the length of the bore. Expand the
stones, as necessary, to compensate for stock removal and stone wear. Stroke at a rate of 30 complete cycles per minute to
produce the best cross‑hatch pattern. Use honing oil generously.
5. Clean cylinder bores with hot water and detergent. Scrub with a stiff bristle brush and rinse with hot water. If the abrasive
material is not washed from the cylinder bore, rapid wear of the new piston rings and cylinder bores will occur. After cleaning,
the bores should be swabbed several times with engine oil and a clean cloth, then wiped with a clean dry cloth. The cylinders
should not be cleaned with kerosene or gasoline.
6. Measure the cylinder bore diameter with a snap gauge micrometer or bore gauge in each of the cylinders. Check for tapered,
out‑of‑round (egg‑shaped), and oversize bore.
Cylinder block finish hone
Standard 88.925 mm (3.501 in.)
Oversize 0.38 mm (0.015 in.) 89.306 mm (3.516 in.)
Maximum taper or out‑of‑round 0.076 mm (0.003 in.)
7. If a cylinder bore is tapered or out‑of‑round more than 0.076 mm (0.003 in.) from the finished hone diameter, it will be necessary
to bore the cylinder oversize.
NOTE: The weight of an oversize piston is approximately the same as a standard size piston. It is not necessary to bore all
the cylinders oversize.
8. After measuring the cylinder bores, apply 2‑Cycle Premium Outboard Oil to the cylinder bores to prevent corrosion.
Tube Ref No. Description Where Used Part No.
14
2-Cycle Premium
Outboard Oil
Cylinder bores after honing 92-858021K01
Pistons and Piston Rings
IMPORTANT: If the engine was submerged while engine was running, the piston pin and/or connecting rod may be bent. If the
piston pin is bent, the piston must be replaced and the connecting rod must be checked to verify it is straight.
1. Inspect the pistons for scoring and excessive piston skirt wear.
2. Check the tightness of the piston ring locating pins. The locating pins must be tight.
3. Thoroughly clean the pistons. Carefully remove the carbon deposits from the pistons with a soft wire brush or carbon removal
solution. Do not burr or round off the machined edges on the piston.
4. Inspect the piston ring grooves for wear and carbon accumulation. If necessary, scrape the carbon from the piston ring
grooves. Be careful not to scratch the sides of the grooves.
Cleaning Piston Ring Grooves
Keystone (tapered) ring grooves:
1. Use a bristle brush and carbon removal solution to remove carbon from the piston surfaces.
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