1977-1982 Honda CT90-CT110 Service & Repair Manual
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SHOP MANUAL
CT90·110
~HONDA
CT90·110
INTRODUCTION
This shop manual contains service i nformation and procedures for 1977 through 1979 CT90's and 1980
through 1982 Honda CT11 O·s. Motorcycles manufactured after December 31. 1977 are equipped with
emission controls. These are covered in this shop manual, in Section VII ('78).02 EMISSIONS ADDENDUM).
CT110 service information begins on page 141.
Date of Issue: Mar. , 1982
© HONDA MOTOR CO., LTD.
1
2
CONTENTS
~HON'DA
CT90·110
SPECIFICATIONS. ................................................... 3
II SERVICE INFORMATION
1. SERVICE DATA ...... •. , . . • • . • . . . . . . . . . . • . . . • . . . . . . . . . . . . . . . . . . . . . .. 5
2. TORQUE SPECIFICATIONS. . . . . . . . . . . . . • . . . . . . . . . . . • . . . . . . . . . . . . . . . . . .. 7
3. SPECIAL TOOLS. . . . . . . . . • • . • . . . . • • . . • . . • . • . • . . • . . • . . . . • . . . . . . . . . . . .. 8
4. LUBRICATION POINTS. . . • . • . . • . . . . . • . . . . . . . • . •. • . . . • . . • . . . . . . . . . . . . .. 9
5. WIRING DIAGRAM ....... ••• ....... •...••..••.• ...................... 10
6. TROUBLE SHOOTING CHART •• ....... •••..• ...... • .................... 11
7. MAINTENANCE SCHEDULE .• . • • . • . . . . . • . . . . . . . . . . . • . . . . . . . . . . . . . . . . .. 20
III INSPECTION/ADJUSTMENT ........................................... 22
IV ENGINE
1. ENGINE REMOVAL/INSTALLATION .... •...•..• .......................... 36
2. CYLINDER HEAD!VALVES ...• ........ • .................... • ........... 38
3. CYLINDER/PISTON ............... •.••.• ............................. 50
4. LUBRICATION SYSTEM .................. •...•..•• .................... 56
5. CLUTCH/GEAR SHIFT/OIL PUMP ........................................ 57
6. AUXILIARY TRANSMISSION ........................ • .................. 65
7. A.C. GENERATOR/CAM CHAIN TENSIONER ................................ 68
8. TRANSMISSION/CRANKSHAFT/KICK STARTER ............. •...• ........... 71
9. CARBURETOR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 78
V FRAME
1. FRONT WHEEL/FRONT SUSPENSION/STEERING ......... • .................. 83
2. REAR WHEEL/REAR SUSPENSION ................. • ..................... 90
3. TAILLIGHT/FUEL TANK ..... • ........................................ 96
4. WIRING • .......................................................... 97
VI ELECTRICAL
1. BATTERY CHARGING SYSTEM .• ........................................ 99
2. IGNITION SYSTEM .• ................................................. 103
3. SWITCHES ......................................................... 106
VII '78% EMISSIONS ADDENDUM' ........................................ 109
VIII '79 ADDENDUM' .................................................... 137
IX '80 CT110 ADDENDUM· ............................................. 141
X '81 CT110 ADDENDUM ............................................... 171
XI '82 CT110 ADDENDUM ............................................. 185
Date ofIssue: Mar., 1982
©HONDA MOTOR CO., LTD.
~HONDA
~ CT90
Items
DIMENSION
Overall Length
Overall Width
Overall Height
Wheel Base
Seat Height
Ground Clearance
Dry Weight
FRAME
Type
Front Suspension, Travel
Rear Suspension, Travel
Front Tire Size, Type
Rear Tire Size, Type
Front Brake
Rear Brake
Fuel Capacity
Fuel Reserve Capacity
Auxiliary Fuel Tank Capacity
Caster Angle
Trail Length
Front Fork Oil Capacity
ENGINE
Type
Cylinder Arrangement
Bore and Stroke
Displacement
Compression Ratio
Carburetor, Venturi Dia.
Valve train
Oil Capacity
Lubri cation System
Fuel Required
Air Filtration
Date of Issue: Oct., 1977
© HONDA MOTOR CO., LTD.
I SPECIFICATIONS
Specifications
1,870 mm ( 73.6 in)
740mm ( 29.1 in)
1,060 mm ( 41.7 in)
1,220 mm ( 48.0 in)
775mm ( 30.5 in)
165 mm ( 6.5 in)
90 kg (198.5 lb.)
Back bone
Telescopic fork, 102 mm (4.0 in)
Swing arm, 77 mm (3.0 in)
2.75-17-4 PR Knobby, tire air pressure 1.75 kg/cm
2
(25 psi)
2.75-17-4 PR Knobby, tire air pressure 2.25 kg/cm
2
(32 psi)
I nternal expanding shoes
Internal expanding shoes
5.5 lit. (1.4 U.S. gal. 1.21 Imp. gal.)
0.18 Imp. gal)
0.54 Imp. gal)
0.8 lit.
2.3 lit.
(0.2 U.S. gal.
(0.6 U.S. gal.
63°
75 mm (3 in)
125 -135 cc (4.2 - 4.6 ozs.)
To fill dry fork assembly
130 - 140 cc (4.4 - 4.7 oz.)
To refill after draining
120 - 130 cc (4.1 - 4.4 oz.)
Air cooled 4-stroke O.H.C. engine
Single cylinder 75 inclined from vertial
50 x 45.6 mm (1.970 x 1.797 in)
89.5 cc (5.46 cu in)
8.2: 1
Piston valve type, venturi dia. 16 mm (0.64 in)
Chain driven over head camshaft
0.9 lit. (0.95 U.S. qt. 0.80 Imp. qt.)
Forced pressure and wet sump
Low-lead or regular gasoline of 91 research octane
(86 pump octane) or higher
Oiled polyurethane foam filter
3
4
Items
Intake Valve : Opens
Closes
Exhaust Valve: Opens
Closes
Valve Clearance
Engine Dry Weight
Air Screw Opening
Pilot Screw Opening
Idle Speed
DRIVE TRAIN
Clutch
Transmission
Primary Reduction
Gear Ratio I
II
III
IV
Auxiliary Transmission High/Low
Final Reduction
Gear Shift Pattern
ELECTRICAL
Ignition
Ignition Advance :
" F " mark
Max. advance
Starting System
Alternator
Battery Capacity
Fuse Capacity
Spark Plug
Condenser Capacity
SPECIFICATIONS
~HONDA
CT90
Specifications
5° BTDC
20° ABDC
25° BBDC
5° ATDC
IN/EX.
0.05 mm (0.002 in)
24 kg (52.9 lb.)
1
[1-1/4]
1,300 rpm
Wet multi plate automatic
4-speed constant mesh
3.722
2.538
1.611
1.190
0.958
1.000 / 1.867
] k9 (1978) model
3.000, drive sprocket 15 T, driven sprocket 45 T
Left foot operated return system
Battery and ignition coil
1,300 rpm
10° TDC
26° - 32°
Kick starter
A.C. Generator 0.062 kw/6,000 rpm
6 V - 5.5 AH
15 amp.
U.S.A. model
D8HA (NGK), X24FS-U (ND)
Canada model
DR8HS (NGK), X24FSR-U (ND)
0.27 -0.33#LF
Date ofIssue: Oct., 1977
CD HONDA MOTOR CO., LTD.
~HONDA
~ CT90
II SERVICE INFORMATION
1.SERVICE DATA
ENGINE Unit· mm (in )
Item Standard Service Limit
I.D. 50.00-50.01 (1.9685 - 1.9689) 50.10 (1.9724)
Cylinder Taper 0-0.01 (0 - 0.0004) 0.05 (0.002)
Out-of-round 0 0.01 (0 0.0004) 0.05 (0.002)
Piston O. D. 49.97-49.99 (1.9673 - 1.9681) 49.80 (1.9606)
Piston pin I. D. 14.002-14.008 (0.5513 -0.5515)
14.04 (0.5528)
Piston pin O. D. 13.994-14.000 (0.5509 - 0.5512) 13.960 (0.5496)
Top/second 0.15-0.35 (0.006 - 0.014) 0.50 (0.020)
Piston ring end gap
Oil 0.15-0.40 (0.006 - 0.016) 0.50 (0.020)
Piston-to-piston ring clearance Top/second 0.010-0.045 (0.0004 - 0.0018) 0.12 (0.0047)
Oil 0.010-0.045 (0.0004 - 0.0018) 0.12 (0.0047)
Piston ring thickness Top/second 1.175-1.190 (0.0463 - 0.0469) 1.130 (0.0445)
Oil 2.475-2.490 (0.0974 - 0.0980) 2.43 (0.957)
Valve stem O. D.
IN 5.455-5.465
(0.2148 - 0.2152) 5.435 (0.2139)
EX 5.435-5.445 (0.2140 - 0.2144) 5.415 (0.2132)
Valve guide I. D. IN/EX 5.475-5.485 (0.2157 - 0.2161) 5.525 (0.2175)
Valve-to-valve guide clearance
IN 0.010-0.030 (0.0004 - 0.0012) 0.08 (0.0032)
EX 0.030-0.050 (0.0012 - 0.0020) 0.10 (0.0040)
Free length
Outer 31.8 (1.252) 30.6 (1.205)
Valve spring
Inner 26.5 (1.043) 25.5 (1.004)
Preload/length Outer kg/mm (lbs.lin.) 19-21/22.3 (41.8-46.21/0.878)
Inner kg/mm (lbs.lin.) 9.5-10.5/18.4 (20.9-23.1/0.724)
Valve face width IN/EX 1.2-1.5 (0.048 - 0.060) 1.8 (0.072)
Valve seat width IN/EX 1.0 (0.04) 1.6 (0.064)
Cam height IN/EX 24.90-24.98 (0.9803 - 0.9835) 24.6 (0.9685)
Camshaft O. D.
R.End 17.927-17.938 (0.7058 - 0.7062) 17.90 (0.7047)
L. End 25.917 - 25.930 (1 .0204 - 1.0209) 25.90 (1.0197)
R. End 18.000-18.018 (0.7087 -0.7094) 18.05 (0.7106)
Camshaft end bearing I. D.
L. End 26.000-26.020 (1.0236 - 1.0244) 26.05 (1.0256)
Clutch disc thickness
2.8-2.9 (0.1102 -0.1142) 2.4 (0.0945)
Clutch plate thickness
1.93-2.07 (0.0760 - 0.0815) 1.85 (0.0729)
Clutch plate warpage 0.2 (0.008) 0.5 (0.02)
I Freelength 27.0 (1.0630) 26.0 (1.0236)
Clutch spring
I Preload/length kg/mm (lbs/in) 10-10.4/15 (22-22.9/0.591 )
Crankshaft run out (at ends) 0-0.015 (0 - 0.0006) 0.10 (0.0040)
Crankshaft bearing play
Axial 0.10-0.35 (0.004 - 0.019) 0.8 (0.032)
Radial O. - 0.01 (0. - 0.0004) 0.05 (0.002)
Connecting rod small end I. D.
14.012-14.028 (0.5517- 0.5523) 14.050 (0.5531)
Connecting rod big end side clearance 0.10-0.35 (0.004 - 0.019) 0.8 (0.032)
Connecting rod big end radial clearance 0-0.01 (0 - 0.0004) 0.05 (0.002)
Clutch drive gear I.D. 24.00-24.02 (0.9449 - 0.9457) 24.15 (0.9508)
Clutch center guide O.D 22.0-22.1 (0.8661 - 0.8701 ) 21.85 (0.8602)
Clutch center guide-to-crankshaft clearance 0.005-0.047 (0.0002 - 0.0019) 0.15 (0.0060)
Date of Issue: Oct., 1977
© HONDA MOTOR CO., LTD.
5
SERVICE DATA
~HONDA
__ CT90
Item Standard Service Limit
Rocker arm shaft O. D. 9.972-9.987 (0.3926 - 0.3932)
9.92 (0.3906)
Rocker arm I. D. 10.000-10.015 (0.3937 - 0.3943) 10.10 (0.3976)
Primary drive gear I. D. 24.00-24.02 (0.945 - 0.946) 24.15 (0.951)
Crankshaft-to-ci utch center guide clearance 0.005-0.047 (0.0002 - 0.0019) 0.15 (0.060)
Tensioner spring free length
Spring A 65 (2.6) 60 (2.4)
Spring B 49.8 (19.92) 40 (1.6)
Inner-to-outer rotor
0.15 (0.006) 0.2 (0.008)
clearance
Oil pump
Outer rotor-to-body
0.15-0.20 (0.0060 - 0.0080) 0.25 (0.010)
clearance
Rotor-to-cover
0.02-0.07 (0.0008 - 0.0028) 0.12 (1.0047)
clearance
Shift fork I. D. 42.00 (1.6535) 42.1 (1.6575)
Shift fork ends thickness 5.96-6.04 (0.2346 - 0.2378) 5.70 (0.2244)
Shift drum O. D. 41.950-41.975 (1.6516 - 1.6526) 41.80 (1.6457)
Shift drum groove width 6.1-6.2 (0.2402 - 0.2441 ) 6.4 (0.2520)
Shift fork-to-shift drum clearance 0.05 (0.0020) 0.2 (0.008)
Auxiliary transmission
Idler gear shaft O. D. 12.966-12.984 (0.5105 - 0.5112) 12.85 (0.5140)
Idler gear I. D. 13.000-13.018 (0.5200 - 0.5207) 13.10 (0.5157)
FRAME
Item Standard Service Limit
Front/rear axle shaft bend 0-0.05 (0 -0.002) 0.2 (0.008)
Axial 0-0.05 (0 - 0.002) 0.1 (0.004)
Front/rear wheel bearing play
Radial 0.003-0.008 (0.0001 - 0.0003) 0.04 (q.0016)
Front/rear brake drum I. D. 110.0 (4.3307) 111.0 (4.3701)
Face runout 0-0.5 (0 -0.02) 1.0 (0.04)
Wheel rim
Eccentricity 0-0.5 (0 - 0.02) 1.0 (0.04)
Front fork spring Free length 203 (8.0) 185 (7.3)
Rear shock absorber spring Free length 223 (8.78) 207 (8.16)
Front fork piston O. D. 30.950-30.975 (1.219 - 1.220) 30.85 (1.215)
Front fork bottom case I. D. 31.000-31.039
(1.221 - 1.223) 31.10 (1.225)
Brake lining thickness 4.0 (0.16) 2.0 (0.08)
G
Date ofIssue: Oct., 1977
CD HONDA MOTOR CO., LTD.
~
HONDA.
CT90
Hoo< 2. TORQUE SPECIFICATIONS
ENGINE
Tightening point Q'ty Thread dia. Torque kg-m (lbs ft)
Cylinder head nut 4 8 2.0 - 2.5 (14.5-18.1)
Camshaft sprocket bolt 2 6 0.9 - 1.2 ( 6.5- 8.7)
Cam chain guide roller bolt 1 6 0.9 - 1.4 ( 6.5 -10.1)
Spark advancer bolt 1 6 0.8 - 1.2 ( 5.8- 8.7)
Clutch lock nut 1 16 3.8 -4.5 (27.4 - 32.5)
A. C. generator rotor bolt 1 8 2.6 - 3.2 (18.S - 23.2)
A. C. generator stator bolt 3 6 0.8 - 1.2 ( 5.8- 8.7)
Shift drum bolt 1 6 0.8 - 1.2 ( 5.8- 8.7)
FRAME
Tightening point Q'ty Thread dia. Torque kg-m (lbs-ft)
Handlebars setting bolts
4 6 0.8 -1.2 ( 5.8- 8.7)
Steering stem nut
1 22 6.0 -7.0 (43.4 - 50.7)
Front fork bolt 2 10 3.5 - 4.5 (25.3 - 32.6)
Steering bottom bridge bolt 2 8 1.8-2.5 (13.0 - 18.1)
Swingarm pivot bolt 1 10 4.0 - 6.0 (29.0 - 43.4)
Rear shock absorber upper nut 2 10 2.5 - 3.5 (18.1 - 25.3)
Rear shock absorber lower nut 2 8 2.5 - 3.5 (18.1 - 25.3)
Front axle nut 1 10 3.5 - 5.0 (25.3 - 36.2)
Rear axle nut 1 10 3.5 - 5.0 (25.3 - 36.2)
Rear axle sleeve nut 1 16 3.5 - 4.5 (25.3 - 32.6)
Driven sprocket bolt 4 8 1.8 - 2.5 (13.0 - 18.1)
Rear brake stop arm bolt 2 8 1.8 - 2.5 (13.0-18.1)
Engine hanger bolt 2 10 3.0 - 4.0 (21.7 - 29.0)
Step bar bolt 14 8 1.8 - 2.5 (13.0 - 18.1)
Torque specifications listed above are important tightening points. Others should be tightened to standard torque
below.
Standard Torque Specifications
Type Torque kg-m (lbs-ft) Type Torque kg-m (lbs-ft)
5 mm bolt and nut 0.45 - 0.60 ( 3.3- 4.3) 5 mm screw 0.35 - 0.50 (2.5 - 3.6)
6 mm bolt and nut 0.8 -1.2 ( 5.8- 8.7) 6 mm screw
0.7 - 1.1 ( 5.1 - 8.0)
8 mm bolt and nut
1.8 -2.5 (13.0-18.1) 6 mm flange bolt and nut 1.0 -1.4 ( 7.2 - 10.1)
10 mm bolt and nut 3.0 -4.0 (21.7 - 29.0) 8 mm flange bolt and nut 2.4 -3.0
(17.4 - 21.7)
12 mm bolt and nut 5.0 --£.0 (36.2 - 43.4) 10 mm flange bolt and nut 3.0 -4.0
(21.7 - 29.0)
Date of Issue: Oct., 1977
© HONDA MOTOR CO., LTD. 7
3. SPECIAL TOOLS
TOOL NAME
Float valve gauge
36mm pin spanner
Tappet adjusting wrench
Steering stem nut wrench
16mm lock nut wrench
Clutch outer holder
Rotor puller
Valve guide driver
Valve guide driver
Valve spring compressor
Valve guide reamer
Bearing driver
Bearing driver attachment
Bearing driver
Bearing driver attachment
Ball race driver
Fork seal driver
Oil seal guide
Rear shock absorber dis/assembling tool
Spring holder
8
PART NO.
07401 - 0010000
07902 - 0010000
07908 - 0010000
07915 - 0300000
07916 - 3710000
07932 - 0340000
07933 - 2160000
07942 - 3290100
07942 -1180100
07957 - 3290001
07984 - 0980000
07949 - 3000000
07945 - 0980000
07949 - 6110000
07945 - 3330100
07944 -1150001
07974 - 1180001
07974 - 1280000
07959 - 3290000
07967 - 1150100
~HONDA
CT90
REFERENCE PAGE
81
86
24
86
58
58
69
42
42
41
42
85,91
85,91
92
92
86
87
43
93
93
Date ofissue: Oct., 1977
CD HONDA MOTOR CO., LTD.
~HOND.A
~ CT90
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This service manual covers the Honda CT90-CT110 models from 1977 to 1982. It provides comprehensive repair information for all aspects of the vehicle. The manual includes detailed step-by-step instructions, diagrams, illustrations, wiring schematics, and specifications, making it valuable for both professional mechanics and DIY enthusiasts.
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