Cleaning And Inspection

Place piston and cylinder in "Gunk Hydro-Seal" or other carbon and gum dissolving agent until deposits are soft. Then thoroughly scrub Diston and cylinder in gasoline or solvent to remove deposits. Where carbon deposit is thick or hard, it is advisable to scrape carbon before cleaning. Use a putty knife-type scraper or a ground tip from an old file. Use extreme care to avoid scraping into aluminum of pistons.

After parts are thoroughly washed, blow dry with compressed air. Force air through oil holes in cylinder. Clean piston ring grooves with a tool for cleaning ring grooves; if not available, sharpen end of a broken ring to a chisel edge. Avoid scratching or damaging sides of ring grooves.

Examine piston pin to see that it is not loose in connecting rod, grooved, pitted or scored. If necessary, remove bushing as described in "Disassembling Cylinder and Piston."

A piston pin, properly fitted, is a light hand press fit in piston and has .001 in. clearance in connecting rod upper bearing.

If difference in diameter of hole in piston pin bushing and diameter of piston pin exceeds a .002 in. fit, replace worn parts.

Replace piston pin lock ring whenever it is removed from piston groove. If opposite side ring has not been removed and is undamaged, it is not necessary to disturb it.

Examine piston and cylinder for cracks, burrs, burned spots on piston dome, grooves and gouges.

Check rods for up-and-down play and upper end side shake (see Fig. 3C-17). To make this check with accuracy, pistons should first be removed. When appreciable up-and-down play is found and side shake (rod tip) at extreme upper end is 11/64 in. or more for front rod or 3/64 in. or more for rear rod, lower bearing should be refitted. This requires removing and disassembling engine crankcase. See "Crankcase," Section 3E.

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