272144 Vanguard Twin Cylinder OHV BRIGGS & STRATTON.pdf

GENERAL INFORMATION
Install new piston rings whenever the engine is
disassembled for major servicing or overhaul,
providing that cylinder bores are within specification.
1. Remove any carbon or ridge at the top of the
cylinder bore. This will prevent breaking the
rings when removing the piston and connecting
rod from the engine.
2. Remove the connecting rod cap. Push the
piston and connecting rod out through the top of
the cylinder.
3. Measure cylinder bores before checking pistons
and rings. If cylinder bores require re-sizing it is
not necessary to check pistons and rings, since
a new oversized piston assembly will be used.
Resize a cylinder bore if it is more than 0.003” (0.08
mm) oversize, or 0.0015” (0.04 mm) out of round.
Disassemble
1. Remove piston rings using Ring Expander
#19340 (1), Fig. 1.
2. Remove oil control ring coil expander and oil
control rings.
Fig. 2
Inspect Piston and Piston Rings
NOTE: If the cylinder is not going to be resized and
the piston shows no signs of scoring, the
piston should be checked.
1. Check side clearance of ring grooves using a
feeler gauge and NEW piston rings (3), Fig. 3.
Replace the piston if the ring groove is worn
beyond specification.
Side Clearance Reject Dimension:
All Except Models 540000, 610000
• Compression Rings – 0.004” (0.10 mm)
• Oil Rings – 0.008” (0.20 mm)
Models 540000, 610000
• Top Compression Ring – 0.009” (0.23 mm)
• Center Compression Ring – 0.006” (0.15 mm)
• Oil Rings – 0.004” (0.10 mm)
Fig. 1
3. Disassemble piston from connecting rod, Fig. 2.
a. Remove piston pin locks (2).
b. Piston pin is a slip fit in piston and
connecting rod.
Keep pistons and connecting rods together as an assembly.
Do not mix.
Fig. 3
2. Check ring end gap, Fig. 4. Clean carbon from
end of rings and insert approximately 1” (25
mm) into cylinder.
End Gap Reject Dimension
All Except Models 540000, 610000
• All Rings – 0.030” (0.76 mm)
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