Cleaning And Inspecting

Place cylinders and pistons in "Gunk Hydro-Seal" or other carbon and gum dissolving agent until deposits are soft. Scrub piston dome and outside of cylinder to remove deposits. Where carbon deposit is thick and hard, it is advisable to scrape carbon before cleaning. Use a putty knife or ground tip on an old file. Use care to keep from scraping into aluminum of piston.

Wash all parts in solvent and blow dry with compressed air. Force air through feed and return oil passages in cylinder. Clean piston ring grooves with a piece of compression ring ground to a chisel shape.

DISASSEMBLING CYLINDER AND PISTON (Figure 3-8)

Strip motorcycle as described in "Stripping Motorcycle for Engine Repair."

Remove cylinder head as described in "Disassembling Cylinder Head."

Remove all cylinder base stud nuts and washers (1) except one on rear cylinder using Cylinder Base Nut Wrench, Part No. 94585-30. Raise front cylinder and piston enough to permit placing a cloth over crankcase opening. This will prevent dirt orpiecesof brokenring from falling into crankcase.

With piston at bottom of stroke, remove cylinder (2) Remove remaining stud nut from rear cylinder. Remove rear cylinder in same manner. Discard cylinder to crankcase gasket (3).

Spring piston rings (4) outward until they clear ring grooves in piston and lift off. Use a commercial ring expander if necessary. On 1972 and earlier models, pry right piston pin lock ring (6) off piston pin using the Piston Lock Ring Tool, Part No. 96780-32A and screwdriver as shown in Figure 3-9. Right end of piston pin has slots for this purpose. On 1973 to early 1977 models, pry piston pin lock rings (6A) from piston groove using two sharp pointed instruments such as awls. On late 1977 and later models use Internal Lock Ring Pliers, Part No. 96215-49 to remove lock rings. Support piston and tap out piston pin (7A) with a suitable drift.

CAUTION — Do not use retaining ring. Part No. 22588-78, in early style pistons, it will fit too loose. Use only in late style pistons marked with the number "7" or "77" on top.

Remove piston pin bushing (9) if necessary (see "Cleaning and Inspecting"), using Piston Pin Bushing Tool, Part No. 95970-32A.

Examine piston pin to see that it is not pitted or scored. Check the piston pin bushing to see that it is not loose in connecting rod, grooved, pitted or scored. A piston pin, properly fitted, is a light hand press fit in piston and has .001 in. clearance in connecting rod upper bearing. If piston pin to bushing free fit exceeds .002 in., replace worn parts, (see "Connecting Rod Bushings").

If piston pin is to be used again, examine lock ring on unslotted end of pin. If ring is tight in its groove it is not necessary to remove it. When a new ring is required, clean ring groove and install ring before pin is installed in piston. The piston pin included with new piston assembly will have lock ring already installed on unslotted end.

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

Check rods for up and down play on lower bearings. See Figure 3-10. When up and down play is detected and male rod has more than 3/64 in. side shake at extreme upper end and female rod has 1/64 in. side shake at extreme upper end, lower bearing should be refitted. This requires removing and disassembling engine crankcase.

Figure 3-10. Checking Connecting Rod Fit REFINISHING CYLINDERS

Gauge pistons and cylinders to see if they are worn to the point where cylinders must be rebored and oversize pistons installed. Inside and outside micrometers used for piston to cylinder fitting should be checked together to be sure they are adjusted to read exactly the same. Subtract piston measurement from bore measurement to obtain clearance. Bore measurement of a cylinder should be taken in ring path, starting about 1 /2 in. from the top of cylinder, measuring front to rear then side to side. Repeat procedure at the center and at the bottom of ring travel (see Figure 3-11). This process will determine if cylinder is out of round or "egged" and will also show any cylinder taper or bulge.

Figure 3-10. Checking Connecting Rod Fit REFINISHING CYLINDERS

Gauge pistons and cylinders to see if they are worn to the point where cylinders must be rebored and oversize pistons installed. Inside and outside micrometers used for piston to cylinder fitting should be checked together to be sure they are adjusted to read exactly the same. Subtract piston measurement from bore measurement to obtain clearance. Bore measurement of a cylinder should be taken in ring path, starting about 1 /2 in. from the top of cylinder, measuring front to rear then side to side. Repeat procedure at the center and at the bottom of ring travel (see Figure 3-11). This process will determine if cylinder is out of round or "egged" and will also show any cylinder taper or bulge.

Figure 3-11. Measuring Cylinder Bore

Pistons are measured front to rear at base of piston skirt as shown in Figure 3-12. Pistons are cam ground to an egged or oval shape so only front and rear surfaces are touching cylinder wall.

Figure 3-12. Measuring Piston

If cylinders are not scuffed, scored and are worn less than .002 in., it is not necessary to rebore oversize at time of cylinder repair. It may be done at time of next complete engine overhaul. If desired, a new piston may be installed to reduce clearance for more quiet operation.

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