7. Do not remove any part which is a press fit in or on a subassembly unless removal
of that part is necessary for repairs or replacement.
8. When removing ball bearings from shafts, it is best to use a bearing puller. When
removing bearings from housings, drive out bearing with a sleeve slightly
smaller than outside diameter of bearing. The end of sleeve or pipe which
contacts bearing must be square. Protect bearings from dirt by keeping them
wrapped in clean cloths.
NOTICE
•
Special attention should be given to the installation of needle bearings.
Direct pressure on the bearing itself may result in distortion or fracture of
its thin shell, resulting in premature failure.
•
Bearings should be pressed in with a bearing insertion tool that is shaped
to properly contact the bearing face.
•
Do all pressing on the stamped face of the bearing.
The construction of the BU7A winch allows for the motor to be removed, repaired
and replaced without removing the gears. Alternatively, gears can be removed and
replaced without disturbing the motor.
The following instructions cover the complete disassembly of the winch. For sub-
assemblies where it is obvious that no new parts are required, do not disassemble.
Even for complete reconditioning, disassembly should proceed only far enough to
allow thorough inspection and replacement of worn or damaged parts.
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Brake Band Replacement
Refer to Dwg. MHP1207.
For winches with automatic brake, remove cotter pin (92) and brake lever pin (133).
Then the following steps apply to all winches:
1. Remove brake lever screws, separate handle and set aside.
2. Remove four capscrews (69) and lockwashers (71).
3. Pull gear case assembly away from drum.
4. Remove brake band assembly (61) from drum.
5. Remove retainer ring (58) from brake band pin (59). Push pin out of brake band.
Set aside brake adjusting screw (57) and trunnion (56).
6. Refer to “INSTRUCTION SHEET” MHD56142 for “Brake Lining Replacement
Procedures”.
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Control Valve Removal
Refer to Dwg. MHP1207.
1. Unscrew the two valve chest cover capscrews (5) and remove valve chest cover
(7) with assembled parts from motor case (28).
2. Remove valve chest gasket (102).
3. Remove reverse valve nut (1) from reverse valve (10).
4. Pull throttle lever (2) and spring (3) from reverse valve.
5. Remove reverse valve (10) and reverse valve ‘O’ rings (8) and (9) from valve chest
cover.
6. Remove thrust washer (13).
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Motor Disassembly
Refer to Dwg. MHP1207.
1. Remove control valve as described in ‘Control Valve Removal’.
2. Using a 7/16 in. -14 thread bolt, remove rotary valve (15) from rotary valve
bushing (14).
3. Unscrew eight motor case capscrews (29) and remove motor case (28)
containing assembled motor from motor mounting bracket (79).
4. Unscrew four cylinder capscrews (21) from any one of the four cylinder heads
(23) and remove the cylinder head, cylinder sleeve (19) and gasket (24).
5. Rotate crank (44) until piston (17) is at top dead center. Push piston wrist pin (18)
out of piston, freeing piston from connecting rod (39). Repeat until all four
cylinders and pistons have been removed freeing the crank (44) and assembled
parts.
6. Using two screw drivers, pry crank pin sleeve (36) from crank and remove
connecting rod rings (38), connecting rods (39) and connecting rod bushing (37).
7. Remove crank bearing (78) (only if replacement is necessary) by supporting inner
ring of bearing and pressing on face of motor pinion.
8. If pinion on crank (44) is damaged or worn, it will be necessary to replace entire
crank.
9. Unscrew four oil wall screws (35) and remove oil wall (33). Removal of the oil wall
is seldom necessary unless reverse valve bushing (12) is to be removed.
10. Rotary valve bushing (14) and reverse valve bushing (12) are press fits in the
motor case and should never be removed unless replacement is necessary. To
remove, heat bushings to 450˚ F (232˚ C) to loosen Loctite®. Support the face of
the motor case that contacts the valve chest cover, and, with a suitable arbor
inserted into motor case and against the face of the bushing, press bushing out
while it is hot.
CAUTION
•
Use an arbor that will clear the bushing keys (30) that project into each
bushing bore in motor case. Pressing bushings out in the opposite direction
or using an arbor that will not clear the bushing keys will result in the keys
being sheared off.
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Rotary Valve Bushing Removal
Refer to Dwg. MHP1463 on page 7, A. Press bushings OUT; B. Housing Supports;
C. Motor Housing; D. Press bushings IN; E. Reverse Valve Bushing; F. Rotary Valve
Bushing.
1. Fabricate one of the two punches shown in Dwg. MHP1461 on page 7, A.
Plain Punch; B. Shoulder guide required to keep punch centered in bushing;
C. Punch with slot; D. Shoulder guide is optional; E. (Not to scale). The first punch
will clear the bushing key (30), the second one has a slot to clear the bushing
key. Press old rotary valve bushing (14) out of motor housing (28).
2. Measure motor housing bore, if greater than 1.313 in. (33.35 mm) replace
housing.
1.23 in.
(31.0 mm)
3.0 in.
(76 mm)
1.0 in.
(25.4 mm)
0.09 in.
(2.3 mm)
1.30 in.
(33.0 mm)
1.0 in.
(25.4 mm)
0.203 in.
(5.2 mm)
3.0 in.
(76 mm)
Plain Punch
Shoulder guide required
to keep punch centered
in bushing
Punch with slot
Shoulder guide is
optional
(Not to scale)
A
B
C
D
E
(Dwg. MHP1461)
Press bushings
OUT
Motor
Housing
Housing
Supports
Press bushings
IN
Reverse
Valve Bushing
Rotary
Valve Bushing
A
B
C
D
E
F
(Dwg. MHP1463)
CAUTION
•
Press rotary valve bushing out from inside motor housing only. Bushing
has a groove to clear bushing key (30).
•
Support motor housing to prevent damage during pressing.
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Reverse Valve Bushing Removal
Refer to Dwg. MHP1463 on page 7.
1. Fabricate one of the two punches shown in Dwg. MHP1461 on page 7, the first
punch will clear the bushing key (30), the second one has a slot to clear the
bushing key. Press old reverse valve bushing (12) out of motor housing (28).
NOTE: This bushing is only 2 inches (51 mm) long.
2. Measure motor housing bore, if greater than 1.313 in. (33.35 mm) replace
housing.
Form MHD56461 Edition 2
7
