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10
10
COUNTERBALANCE SYSTEMS
Two styles of counterbalance systems are used
on Vertical crankshaft engines.
Models 280000 and 310000 (built before July
2001) have the Synchro-Balance® system.
Models 280000 and 310000 built July 2001 and
later, and all models 210000 and 330000 have
the AVS® system. Both systems use a
counterweight that oscillates opposite the
direction of the piston, to reduce engine vibration
(Figure 25).
Figure 25
Synchro-Balance® System
Remove Counterbalance System
1. Remove blower housing, flywheel,
cylinder head, and sump. Discard gaskets.
2. Remove connecting rod and piston
assembly.
3. Remove crankshaft and counterweight
assembly.
Figure 26
Disassemble
1. Remove crankshaft gear (A, Figure 26).
NOTE: If gear is tight, pry it off using two
screwdrivers being careful not to damage gear.
2. Woodruff key (B) can be removed, if
required.
3. Remove screw (A, Figure 27) from
counterweight.
4. Remove PTO counterweight (B), dowel
pin (C), and link (D) from crankshaft.
5. Remove crankshaft from magneto
counterweight (E).
Figure 27
Inspect
1. Visually inspect counterweight bearings
for scoring or discoloration. If found,
replace both counterweights as a set.
2. Measure the counterweight bearing
diameters and compare to the values
shown in Section 12 - Engine
Specifications. If either bearing is worn
beyond the reject dimensions, replace
both counterweights as a set.
3. Measure the crankshaft eccentric
diameters and compare to the values
shown in Section 12 - Engine
Specifications.
4. If crankshaft eccentrics are worn, scored,
or discolored, replace the crankshaft.