Pistons - Rings - Rods - Briggs & Stratton Twin Cylinder L-Head Repair Manual

PISTONS - RINGS - RODS

GENERAL INFORMATION
REMOVE PISTON AND CONNECTING ROD
Piston Identification
Remove Connecting Rod
Remove Rings
CHECKING PISTONS & RINGS
Check Piston . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Check Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Check Piston Pin and Piston Pin Bore
Check Connecting Rod
ASSEMBLE PISTON & CONNECTING ROD
Assemble Rings to Piston
Install Piston and Connecting Rod Assembly
Torque Connecting Rods
GENERAL INFORMATION
It is recommended that new piston rings be installed whenever the engine is disassembled for major servicing or
overhaul, providing that cylinder bores are within specification.
IMPORTANT: Opposed twin cylinder engines manufactured after date code 00121200 use pistons with narrower ring
grooves and thinner piston rings. Pistons and piston rings used in engines manufactured after date code 00121200
may be used on engines manufactured before code date 00121300 only as an assembly.
Measure cylinder bores before checking pistons and rings. See Section 10. If cylinder bore(s) require re-sizing it will
not be necessary to check pistons and rings since a new oversized piston assembly will be used.
If the cylinder bore is more than.003" (.08 mm) oversize, or .0015" (.04 mm) out of round on cast iron sleeve cylinders,
or .0025" (.06 mm) out of round on aluminum bore cylinders, it must be resized.
REMOVE PISTON AND CONNECTING ROD
When servicing pistons, rings, piston pins or connecting rods, make sure that each connecting rod, piston, piston pin
and ring set be kept as a set for the cylinder from which it was removed. Mark each set, before removing from the
engine.
To remove the piston and connecting rod from the engine, remove the connecting rod cap. Remove any carbon or
ridge at the top of the cylinder bore: this will prevent breaking the rings. Push the piston and rod out through the top of
the cylinder.
NOTE: Connecting rod locks are not used in twin cylinder engines. Special thin washers are used under the
connecting rod cap screws.
Piston Identification
Briggs & Stratton twin cylinder engines use die cast aluminum cylinder blocks with either aluminum bore cylinders or
cast iron sleeve cylinders. The two different cylinder bore materials require different ring sets and piston assemblies.
THEY ARE NOT INTERCHANGEABLE.
Model Series 401400, 401700, 421400 and 421700
have aluminum bore cylinders.
9904
Section 12
Section Contents
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