Yamaha VMX12 93 Manual

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FOREWORD
This Supplementary Service Manual has been prepared to introduce new service and data for the
VMX12 ’93. For complete service information procedures it is necessary to use this Supplementary
Service Manual together with the following manual.
VMX12 ’86 SERVICE MANUAL: 2EN-ME1
VMX12 ’91 SUPPLEMENTARY SERVICE MANUAL: 2EN-AE1
VMX12 ’93
SUPPLEMENTARY
SERVICE MANUAL
1992 by Yamaha Motor Co., Ltd.
1st Edition, November 1992
All rights reserved.
Any reprinting or unauthorized use
without the written permission of
Yamaha Motor Co., Ltd.
is expressly prohibited.

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CAUTION:
NOTICE
This manual was written by Yamaha Motor Company Ltd. primarily for use by Yamaha dealers and
qualified mechanics. It is not possible to put an entire mechanic’s education into one manual, so per-
sonsusingthisbooktoperformmaintenanceandrepairsonYamahamotorcyclesshouldhaveabasic
understanding of the mechanical concepts and procedures inherent in motorcycle repair technology.
Without such knowledge, attempted repairs or service to the motorcycle may render it unfit to use
and/or unsafe.
Yamaha Motor Company Ltd. is continually striving to improve all models manufactured by Yamaha.
Modifications and significant changes in specifications or procedures will be forwarded to all Autho-
rized Yamaha dealers and will, where applicable, appear in future editions of this manual.
PARTICULARLY IMPORTANT INFORMATION
This material is distinguished by the following notation.
The Safety Alert Symbol means ATTENTION! BECOME ALERT! YOUR
SAFETY IS INVOLVED!
Failureto followWARNINGinstructions couldresultinsevereinjury ordeathto
the motorcycle operator, a bystander, or a person inspecting or repairing the
motorcycle.
ACAUTION indicates specialprecautions that mustbe taken toavoiddamage
to the motorcycle.
NOTE: A NOTE provides key information to make procedures easier or clearer.

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HOW TO USE THIS MANUAL
CONSTRUCTION OF THIS MANUAL
This manual consists of chapters for the main categories of subjects. (See “Illustrated symbols”)
1st title 1: This is a chapter with its symbol on the upper right of each page.
2nd title 2: This title appears on the upper of each page on the left of the chapter symbol.
(For the chapter “Periodic inspection and adjustment” the 3rd title appears.)
3rd title 3: This is a final title.
MANUAL FORMAT
Alloftheproceduresinthismanualareorganizedinasequential,step-by-stepformat.Theinformation
has been compiled to povide the mechanic with an easy to read, handy reference that contains com-
prehensive explanations of all disassembly, repair, assembly, and inspections.
Asetof particularly important procedure 4is placed between a lineof asterisks “ ” with eachproce-
dure preceded by “”.
IMPORTANT FEATURES
Data and a special tool are framed in a box preceded by a relevant symbol 5.
Anencirclednumeral 6indicatesapartname,andanencircledalphabeticalletterdataoranalign-
ment mark 7, the others being indicated by an alphabetical letter in a box 8.
Aconditionofafaultycomponentwillprecedeanarrowsymbolandthecourseofactionrequiredthe
symbol 9.
EXPLODED DIAGRAM
Eachchapterprovidesexplodeddiagramsbeforeeachdisassemblysectionforeaseinidentifyingcor-
rect disassembly and assembly procedures.

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21
1
3
5
7
9
2
4
8
6
23
2220
18 1917
15
1413
11 12
10
GEN
INFO SPEC
ENG
CARB
ELECCHAS
COOL
INSP
ADJ
TRBL
SHTG
16
24
ILLUSTRATED SYMBOLS
(Refer to the illustration)
Illustrated symbols 1to 9are designed as
thumb tabs to indicate the chapter’s number
and content.
1General information
2Specifications
3Periodic inspection and adjustment
4Engine
5Cooling system
6Carburetion
7Chassis
8Electrical
9Troubleshooting
Illustrated symbols 10 to 16 are used to identify
the specifications appearing in the text.
10 Filling fluid
11 Lubricant
12 Special tool
13 Tightening
14 Wear limit, clearance
15 Engine speed
16 Ω, V, A
Illustratedsymbols 17 to 24 in the explodeddia-
gram indicate grade of lubricant and location of
lubrication point.
17 Apply engine oil
18 Apply gear oil
19 Apply molybdenum disufide oil
20 Apply wheel bearing grease
21 Apply lightweight lithium-soap base grease
22 Apply molybdenum disulfide grease
23 Apply locking agent (LOCTITE)
24 Use new one

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CONTENTS
GENERAL INFORMATION 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MOTORCYCLE IDENTIFICATION 1. . . . . . . . . . . . . . . . . . . . . . . . . . . .
VEHICLE IDENTIFICATION NUMBER (For E) 1. . . . . . . . . . . . . . .
FRAME SERIAL NUMBER (Except for E) 1. . . . . . . . . . . . . . . . . . .
ENGINE SERIAL NUMBER 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPECIAL TOOL 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FOR CHASSIS SERVICE 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPECIFICATIONS 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GENERAL SPECIFICATIONS 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MAINTENANCE SPECIFICATIONS 4. . . . . . . . . . . . . . . . . . . . . . . . . . .
ENGINE 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CHASSIS 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ELECTRICAL 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CHASSIS 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FRONT AND REAR BRAKE 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FRONT FORK 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
REMOVAL 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DISASSEMBLY 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
INSPECTION 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ASSEMBLY 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
INSTALLATION 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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–1–
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MOTORCYCLE IDENTIFICATION GEN
INFO
NOTE:
NOTE:
NOTE:
GENERAL
INFORMATION
MOTORCYCLE IDENTIFICATION
VEHICLE IDENTIFICATION NUMBER (For E)
Thevehicleidentificationnumber 1isstamped
into the steering head pipe.
Starting serial number:
JYA2ENS0-PA041101
The vehicle identification number is used to
identify your motorcycle and may be used to
register your motorcycle with the licensing au-
thority in your state.
FRAME SERIAL NUMBER
(Except for E)
The frame serial number 1is stamped into the
right side of steering head.
Starting serial number:
2EN-031101 (F) (I) (B) (PRT) (GB)
The first three digits of these numbers are for
model identifications; the remaining digits are
the unit production number.
ENGINE SERIAL NUMBER
Theengineserialnumber 1isstampedintothe
left side of the engine.
Starting serial number:
2EN-031101 (F) (I) (B) (PRT) (GB)
2EN-041101 (E)
The first three digits of these numbers are for
model identifications; the remaining digits are
the unit production number.
Designs and specifications are subject to
change without notice.

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SPECIAL TOOLS GEN
INFO
Refer to the list provided to avoid errors when
placing an order.
P/N. YM-jjjjj, YU-jjjjj For USA,
YS-jjjjj, YK-jjjjj Califo-
mia,
ACC-jjjjj CDN
P/N. 90890-jjjjj For EUR,
AUS
11
2
T-Handle
P/N. YM-01326
P/N. 90890-01326
For damper rod
holder (29 mm)
P/N. YM-33962
P/N. 90890-01375
These tools are used to loosen and tighten
the front fork damper rod holding bolt.
Front fork seal driver
(weight)
P/N. YM-33963
P/N. 90890-01367
Adapter (43 mm)
P/N. YM-8020
P/N. 90890-01374
These tools are used when installing the
fork seal:
2
1
2
SPECIAL TOOLS
Theproperspecialtoolsarenecessaryforcom-
plete and accurate tune-up and assembly. Us-
ing the correct special tool will help prevent
damage caused by the use of improper tools or
improvised techniques.
Theshapeandpartnumberusedforthespecial
tooldifferby country, sotwotypes areprovided.
FOR CHASSIS SERVICE

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GENERAL SPECIFICATIONS SPEC
SPECIFICATIONS
GENERAL SPECIFICATIONS
Model VMX12
Model code number:
Engine starting number:
Frame starting number:
Vehicle identification number:
3LR8 (F) (I) (B) (PRT) (GB)
3LR9 (E)
2EN-031101 (F) (I) (B) (PRT) (GB)
2EN-041101 (E)
2EN-031101 (F) (I) (B) (PRT) (GB)
JYA2ENS0 PA041101 (E)
Minimum turning radius: 2,900 mm (114 in)
Tire:
Type
Size (F)
Size (R)
Wear limit
Tubeless
110/90V 18
METZELER/ME33
150/90VB 15 M/C
METZELER/ML2
1.0 mm (0.04 in)

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MAINTENANCE SPECIFICATIONS SPEC
MAINTENANCE SPECIFICATIONS
ENGINE
Model VMX12
Carburetor:
I.D. Mark
Main jet (M.J.)
Main air jet (M.A.J.)
Jet needle (J.N.)
Needle jet (N.J.)
Pilot jet (P.J.)
Pilot air jet (P.A.J.1)
Pilot screw (P.S.)
Pilot outlet (P.O.)
Bypass 1 (B.P.1)
Bypass 2 (B.P.2)
Bypass 3 (B.P.3)
Valve seat size (V.S.)
Starter jet (G.S.1)
Starter jet (G.S.2)
Fuel level (F.L.)
Engine idling speed
Vacuum pressure at idling speed
3LR-01
#150
ø2.0
5DZ19-3
Y-0
#42.5
#95
2 and 1/2 turn out
0.9
0.8
0.8
0.9
1.5
#45
#0.8
15 17 mm (0.59 0.66 in)
950 1,050 r/min
200 mm Hg (7.87 in Hg)
CHASSIS
Model VMX12
Front suspension:
Front fork travel
Fork spring free length
<Limit>
Collar length
Spring rate: K1
K2
Stroke K1
K2
Optional spring
Oil capacity
Oil level
Oil grade
Enclosed air pressure (standard)
<Min. Max.>
140 mm (5.51 in)
386.5 mm (15.2 in)
<381.5 mm (15.0 in)>
245 mm (9.65 in)
3.75 N/mm (0.375 kg/mm, 21.0 lb/in)
4.90 N/mm (0.5 kg/mm, 28.0 lb/in)
0 78 mm (0 3.07 in)
78 140 mm (3.07 5.51 in)
No.
619 cm3(21.8 lmp oz, 20.9 US oz)
123 mm (4.8 in)
Yamaha fork oil 10wt or equivalent
39.2 kPa (0.4 kg/cm2, 5.7 psi)
<39.2 98.1 kPa (0.4 1.0 kg/cm2, 5.7 14.2 psi)>
Front disc brake:
Type
Disc outside diameter thickness
Pad thickness Inner
<Limit>
Pad thickness Outer
<Limit>
Dual
298 5.0 mm (11.7 0.20 in)
5.0 mm (0.20 in)
<0.5 mm (0.02 in)>
5.0 mm (0.20 in)
<0.5 mm (0.02 in)>
Master cylinder inside diameter
Caliper cylinder inside diameter
Brake fluid type
15.87 mm (0.63 in)
33.96 + 30.23 mm (1.33 + 1.19 in)
DOT #4 or DOT #3

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MAINTENANCE SPECIFICATIONS SPEC
ELECTRICAL
Model VMX12
T.C.I.:
Pickup coil resistance (color)
T.C.I. Unit-model/Manufacturer 81 121 Ωat 20_C (68_F) (Black – Orange)
BB7224/HITACHI

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FRONT AND REAR BRAKE CHAS
1Air bleed screw
2Retaining pin
3Dust seal
4Piston seal
5Piston
6Brake pad
7Pad spring
8Caliper assembly
9Brake disc
E The arrow mark on the pad
spring must point in the disc ro-
tating direction.
A FRONT CALIPER
BPAD WEAR LIMIT:
0.5 mm (0.02 in)
C
D
MINIMUM DISC THICKNESS:
4.5 mm (0.18 in)
MAXIMUM DEFLECTION:
0.3 mm (0.01 in)
35 Nm (3.5 mkg, 25 ftlb)
20 Nm (2.0 mkg, 14 ftlb)
20 Nm (2.0 mkg, 14 ftlb)
35 Nm (3.5 mkg, 25 ftlb)
EPAD SPRING
5 Nm (0.5 mkg, 3.6 ftlb)
CHASSIS
FRONT AND REAR BRAKE

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FRONT FORK CHAS
1Front fork assembly
2Inner fork tube
3Piston metal
4Dust cover
5Retaining clip
6Oil seal
7Seal spacer
8Slide metal
23 Nm (2.3 mkg, 17 ftlb)
AFORK OIL (EACH):
BCAPACITY:
619 cm3(21.8 lmp oz, 20.9 US oz)
CGRADE:
Yamaha Fork Oil 10wt or equivalent
DSTD. AIR PRESSURE:
39.2 kPa (0.4 kg/cm2, 5.7 psi)
EMIN. TO MAX. AIR PRESSURE:
39.2 98.1 kPa
(0.4 1.0 kg/cm2, 5.7 14.2 psi)
FFORK SPRING FREE
LENGTH (LIMIT):
381.5 mm (15.0 in)
20 Nm (2.0 mkg, 14 ftlb)
23 Nm (2.3 mkg, 17 ftlb)
62 Nm (6.2 mkg, 45 ftlb)
FRONT FORK
9Outer fork tube
10 Oil lock piece
11 Damper rod
12 Fork spring
13 Spring seat
14 Collar
15 Cap bolt
16 Fork cap

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FRONT FORK CHAS
WARNING
NOTE:
REMOVAL
Securely support the motorcycle so there is
no danger of it falling over.
1. Place the motorcycle on a level place.
2. Elevate the front wheel by placing suitable
stand under the engine.
3. Remove:
Caliper assembly 1
Brake hose holder 2
4. Disconnect:
Speedometer cable 3
Do not depress the brake lever when the wheel
is off the motorcycle otherwise the brake pads
will be forced shut.
5. Loosen:
Pinch bolt 1(wheel axle)
6. Remove:
Wheel axle 2
Front wheel assembly
7. Remove:
Front fender 1
Fork brace 2
8. Remove:
Fork cap 1
Depress the valve 2until all of the air has
been released.

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FRONT FORK CHAS
WARNING
CAUTION:
NOTE:
9. Loosen:
Pinch bolt 1(handle crown)
Cap bolt 2
Pinch bolts 3(under bracket)
Support the fork before loosening the pinch
bolts.
DISASSEMBLY
1. Remove:
Cap bolt 1
Spacer 2
Spring seat 3
Spring 4
2. Drain:
Fork oil
3. Remove:
Dust seal
Retaining clip 1
Use a thin slotted head screw driver.
Take care not to scratch the inner tube.
4. Remove:
Bolt (damper rod)
Copper washer
Loosen the bolt (damper rod) while holding the
damper rod with the T-handle and holder.
T-handle:
YM-01326
90890-01326
Holder (29 mm):
YM-33962
90890-01375
5. Remove:
Inner fork tube

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FRONT FORK CHAS
CAUTION:
WARNING
Removal steps:
FHold the fork leg holizontally.
FClamp the caliper mounting boss of the outer
tube securely in a vise with soft jaws.
FPullouttheinnerforktubefromtheoutertube
by forcefully, but carefully, with drawing the
inner tube.
SExcessive force will damage the oil seal
and/or the bushes. Damage oil seal and
bushing must be replaced.
SAvoid bottoming the inner tube in the outer
tube during the above procedure, as the oil
lock piece will be damaged.
6. Remove:
SOil seal 1
SSeal spacer 2
SSlide metal 3
SPiston metal
SDamper rod
SOil lock piece
INSPECTION
1. Inspect:
SInner fork tube
SOuter fork tube
Scratches/Bends/Damage Replace.
Do not attempt to straighten a bent inner
fork tube as this may dangerously weaken
the tube.
2. Measure:
SFork spring
Over specified limit Replace.
Fork spring free length (limit):
381.5 mm (15.0 in)

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FRONT FORK CHAS
NOTE:
CAUTION:
3. Inspect:
Damper rod
Wear/Damage Replace.
Contamination Blow out all oil passages
with compressed air.
4. Inspect:
Oil lock piece
O-ring (cap bolt)
Wear/Damage Replace.
ASSEMBLY
Reverse the “DISASSEMBLY” procedure.
Note the following points.
In front fork reassembly, be sure to use follow-
ing new parts.
* Piston metal
* Slide metal
* Oil seal
* Dust seal
Make sure that al components are clean be-
fore reassembly.
1. Install:
Damper rod
Allow the damper rod to slide slowly down
theinnerforktubeuntil it protrudes from the
bottom, being careful not to damage the in-
ner fork tube.

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FRONT FORK CHAS
NOTE:
NOTE:
CAUTION:
2. Lubricate:
Inner fork tube (outer surface)
Recommended lubricant:
Fork oil 10w or equivalent
3. Install:
Piston metal 1
Oil lock piece 2
4. Tighten:
Bolt (damper rod)
Bolt (damper rod):
62 Nm (6.2 mkg, 45 ftlb)
LOCTITE
Tighten the bolt (damper rod) while holding the
damper rod with the T-handle and holder.
T-handle:
YM-01326
90890-01326
Holder (29 mm):
YM-33962
90890-01375
5. Install:
Slide metal
Seal spacer
Oil seal 1
Use the fork seal driver weight and adapter
Fork seal driver weight:
YM-33963
90890-01367
Adapter (43 mm):
YM-8020
90890-01374
Before installing the oil seal, apply the lithium
soap base grease onto the oil seal lips.
Be sure that the oil seal numbered side face
upward.