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Welcome to the 1970 Yamaha AT1-B 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 AT1-B Specifications
Model 1969 Yamaha AT1-B
Dimensions:
Overall Length 77.2 In.
Overall Width 35.8 In.
Overall Height 42.9 In.
Wheelbase 50.6 In.
Min. Ground Clearance 8.9 In.
Weight:
Gross 234 Lbs.
Net 218 Lbs.
Performance:
Max, Speed 65 MPH +
Fuel Consumption 114 MPG @ 25 MPH
(On paved level roads)
Climbing Ability 30 Degree
Min. Turning Radius 75.1 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 7.5 cu. in. (123cc)
Bore X Stroke 2.205 X 1.969 In. (56 X 50MM)
Compression Ratio 7.1:1
Max Power 11.5 BHP/7,500 RPM
Max Torque 8.5 Ft.-Lbs/6,000 RPM
Piston Skirt Clearance .0016 - .0018 In. / 0.40 - 0.45MM
Starting System Primary-Coupled Kick
Ignition Timing B.T.D.C 1.8MM +/- .1MM
NGK Spark Plug & Gap B-8E 0.5-0.6 MM
Contact Break Point Gap 0.011 - 0.013 Inch / 0.30 - 0.35 MM
Volt Reg. Adjustment 15.8 - 16.5V @ 2,500 RPM
(Volts @ RPM - No load)
Cutout Relay Adjustment 13 +/- 0.5 Volts (Cut in Voltage)
Condenser Capacity .22UF (Microfarad)
Carburetor:
Type VM24SH
Main Jet # 150
Jet Needle 4D3-3
Air Jet -
Needle Jet N-8
Cut Away 2.0
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 3.181 (35/11) 39.9
2nd Gear teeth & Ratio 2.000 (30/15) 25.00
3rd Gear teeth & Ratio 1.368 (26/19) 17.1
4th Gear teeth & Ratio 1.000 (23/23) 12.50
5th Gear teeth & Ratio 0.800 (20/25) 10.0
Secondary reduction system Chain
Secondary reduction ratio 3.214 (45/14)
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 4.72 In. / 120MM
Braking System:
Type of brake Internal Expansion
Front Operation System Right hand operation
Rear Operation System Right foot operation
Tire Size:
Front 3.00 - 18 - 4PR Trials Universal
Rear 3.25 - 18 - 4PR Trials Universal
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 GS-114
Manufacturer Hitachi Ltd.
Battery:
Model 12N7-3B (BRT3-12E)
Manufacturer Furukawa Battery
Capacity 12V 7AH
Lighting:
Head Light 12V 25W/25W
Tail Light 12V 7W
Stop Light 12V 23W
Meter Light 12V 3W X 2
High Beam Indicator Light 12V 1.5W
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 AT1B/AT1M-B Owner's Manual is Located: CLICK HERE
The 1970 Yamaha AT1B/AT1M-B Service Manual is Located: CLICK HERE
The 1969-1971 Yamaha AT1-CT1 Combined Service Manual is Located: CLICK HERE
The 1969-1971 Yamaha AT1-CT1 Parts Manual is Located: CLICK HERE
The 1970 Cycle Buyers Guide is Located: CLICK HERE
The 1970 Yamaha AT1B Line-Up Advertisement # 1 is Located: CLICK HERE
The 1970 Yamaha AT1B Advertisement #2 is Located: CLICK HERE
The 1970 Yamaha AT1B advertisement #3 is Located: CLICK HERE
The 1970 Yamaha AT1B Advertisement #4 is Located: CLICK HERE
1970 Yamaha AT1B Autolube adjustment and color codes are Located: CLICK HERE
The USA 1970 Yamaha AT1-B Brochure is Located: CLICK HERE
The 1970 Yamaha Full Line Up Brochure is Located: CLICK HERE
The 1970 Yamaha Enduro Full Line Up Brochure is Located: CLICK HERE
The Canada 1970 Yamaha AT1-B Brochure is Located: CLICK HERE
The 1970 Yamaha AT1-B Crankshaft Data is Located: CLICK HERE
The 1970 Yamaha AT1-B Store is Located: CLICK HERE
