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Welcome to the 1970 Yamaha AT1B-M 125cc MX Forum. Feel free to post anything related to this model in the category. Anything new, will be added to this section. If you see any errors, please contact me privately. There were many errors, in the early Yamaha literature. I will make some error's of my own.
1970 Yamaha AT1B-M Specifications
Model 1970 Yamaha AT1BM
Dimensions:
Overall Length 76.4 In.
Overall Width 35.8 In.
Overall Height 43.1 In.
Wheelbase 50.8 In.
Min. Ground Clearance 9.1 In.
Weight:
Gross 218 Lbs.
Net 202 Lbs.
Performance:
Max, Speed 60 MPH +
Fuel Consumption 114 MPG @ 25 MPH
(On paved level roads)
Climbing Ability 30 Degree
Min. Turning Radius 74.8 In.
Braking Distance 58.3 Ft. @ 31 MPH
Engine:
Model AT1
Type 2 Stroke, Gasoline
Lubricating System Separate (Yamaha Autolube)
Cylinder Single, forward inclined 5 Port
Displacement 7.51 cu. in. (123cc)
Bore X Stroke 2.205 X 1.969 In. (56 X 50MM)
Compression Ratio 8.0:1
Max Power 18.2 BHP/8,500 RPM
Max Torque 14.8 Ft.-Lbs/7,500 RPM
Piston Skirt Clearance .0016 - .0020 In. / 0.40 - 0.50MM
Starting System Primary-Coupled Kick
Ignition Timing B.T.D.C 2MM +/- .1MM
NGK Spark Plug & Gap B-9E 0.5-0.6 MM
Contact Break Point Gap 0.011 - 0.013 Inch / 0.30 - 0.35 MM
Volt Reg. Adjustment -
(Volts @ RPM - No load)
Cutout Relay Adjustment -
Condenser Capacity .3UF +/- 10% (Microfarad)
Carburetor:
Type VM26SH
Main Jet # 190
Jet Needle 4F15-3
Air Jet -
Needle Jet N - 8
Cut Away 1.5
Pilot Jet # 30
Air Screw (turns out) 1 1/2
Starter Jet # 40
Float Level 25.5MM
Intake:
Air Cleaner Wet, Foam Rubber
Transmission:
Clutch Wet, Multiple Disk
Primary reduction system Helical Gear
Primary reduction ratio 3.894 / (74/19) Teeth
Trans Oil Capacity .78 Qts
Gear Box:
Type Constant Mesh, 5 Speed Forward
1st Gear teeth & Ratio 2.833 (34/12) 33.09
2nd Gear teeth & Ratio 1.875 (30/16) 21.90
3rd Gear teeth & Ratio 1.368 (26/19) 15.98
4th Gear teeth & Ratio 1.091 (24/22) 12.73
5th Gear teeth & Ratio 0.957 (22/23) 11.17
Secondary reduction system Chain
Secondary reduction ratio 3.000 (45/15)
Chassis:
Frame Tubular-Double Loop
Front Suspension System Front Telescopic fork
Rear Suspension System Swinging Arm
Fork Oil Capacity 160cc (5.4 Oz.)
Front Cushion System Coil Spring / Oil Damper
Rear Cushion System Coil Spring / Oil Damper
Steering System:
Steering Angle 49 Degrees both left & right
Caster 60.5 Degrees
Trail 4.84 In. / 123MM
Braking System:
Type of brake Internal Expansion
Front Operation System Right hand operation
Rear Operation System Right foot operation
Tire Size:
Front 3.25 - 18 - 4PR Knobby
Rear 3.50 - 18 - 4PR Knobby
Front Tire Pressure 14 P.S.I
Rear Tire Pressure 17 P.S.I
Oil Pump:
Adjustment Stroke Min 0.20 - 0.25 MM
Adjustment Stroke Max 1.85 - 2.05 MM
Dynamo:
Model F130
Manufacturer Hitachi Ltd.
Battery:
Model -
Manufacturer -
Capacity -
Lighting:
Head Light -
Tail Light -
Stop Light -
Meter Light -
High Beam Indicator Light -
Tanks:
Gasoline Tank Capacity 1.9 Gallons
Oil Tank Capacity 1.3 Quarts
Chain:
Tension (Up & down free play) 20MM (25/32)
The 1970 Yamaha AT1BM Owner's Manual is Located: CLICK HERE
The 1970 Yamaha AT1BM Service Manual is Located: CLICK HERE
The 1970 Yamaha AT1B-M Combined Service Manual is Located: CLICK HERE
The 1970 Yamaha AT1BM Combined Parts Manual is Located: CLICK HERE
The 1970 Yamaha AT1BM Advertisement #1 is Located: CLICK HERE
The 1970 Yamaha AT1BM Autolube Adjustment & Color Codes are Located: CLICK HERE
The USA 1970 Yamaha AT1BM Brochure is Located: CLICK HERE
The 1970 Yamaha AT1BM Crankshaft Data is Located: CLICK HERE
The 1970 Yamaha Full Line Up Brochure is Located: CLICK HERE
The 1970 Cycle Buyers Guide is Located: CLICK HERE
The 1970 Yamaha AT1BM Line-Up Advertisement is Located: CLICK HERE
The 1970 Yamaha AT1BM Store is Located below
