Cleaning; Piston; Connecting Rod; Inspection - Briggs & Stratton Vanguard 10V300 Repair Manual

Cleaning

Piston

1. Do not sand blast or glass bead blast piston. Bead
blasting rounds the ring lands and will result in high
oil consumption and blow-by of exhaust gases. Blow-
by of exhaust gases contaminates the engine oil
supply, and reduces engine efficiency by weakening
the combustion seal necessary for efficient transfer of
energy to the piston.
2. To remove all carbon and combustion deposits, soak
the piston in a special detergent that will not corrode
aluminum. Maintain the temperature of the cleaning
solution well below 212° F. (100° C.).
3. Thoroughly rinse the piston and dry with moisture free
compressed air.
4. Thoroughly clean the three piston ring grooves of all
carbon deposits. A broken compression ring properly
ground to a sharp chisel-like edge can be used for
this purpose.
6
5. Verify that the piston pin lock ring groove is clean and
free of dirt and grime.
6. Clean oil drain back holes leading from the oil control
ring groove to the underside of the piston crown. Use
a soft bristle brush and compressed air to ensure
cleanliness. Do not use a wire brush or the holes may
be enlarged.
7. If present, verify that set of oil drain back holes at top
of piston skirt are clean and open.

Connecting Rod

1. Thoroughly clean parts in a non-volatile cleaning
solution or solvent. Follow up with a thorough wash in
hot soapy water.
2. Blow dry with low pressure compressed air.
3. Verify that oil holes in connecting rod shank and at
top of piston pin bore are clean and open.

Inspection

Piston and Pin

1. Carefully inspect the piston for damage or excessive
wear. Proceed as follows:
A. Inspect the piston for cracks. Pay special
attention to the area around the pin bores and oil
drain back holes beneath the piston crown.
B. Check piston for cracked, broken or bent ring
lands.
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63
C. Check piston skirt for cracks, gouges, deep
scratches or heavy scoring.
D. Check piston head for evidence of burning,
etching or melting.
E. Look for marks or imprints caused by contact with
valves.
NOTE: A piston with superficial wear marks, minor
scratching or mild scoring may continue to be used.
2. Lightly oil a good piston pin and insert it into the
piston pin bore to feel for proper fitment. The pin
should slide in and out without binding, but also
without pivoting or rocking.
3. See A of Figure 63. Using an inside micrometer or
dial vernier caliper, measure the piston pin bore
diameter at two locations- parallel and perpendicular
to the crankshaft. Replace the piston if either
measurement is 0.574 inches (14.576 mm) or more.
4. See B of Figure 63. Using an outside micrometer,
measure the outside diameter of the piston pin at
two locations- parallel and perpendicular to the
crankshaft. Replace piston pin if either measurement
is 0.570 inches (14.467 mm) or less.
5. Run your index finger around the edge of the piston
crown to feel for dings, nicks or burrs. Lightly file the
edge of the crown to remove any defects.
6. Measure the piston ring side clearance as follows:
NOTE: Worn ring grooves result in high oil
consumption and blow-by of exhaust gases. Blow-
by of exhaust gases contaminates the engine oil
supply, and reduces engine efficiency by weakening
the combustion seal necessary for efficient transfer of
energy to the piston.
A. See Figure 64. Insert the edge of a new
compression ring into the top piston ring groove.
Insert a feeler gauge between the upper surface
of the ring and the ring land.