Welcome to the 1970 Yamaha AT1-B Forum. The factory paint color was called "Competition Yellow". The USA vin number range is: AT1-120101 to 138890. 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.

                    1970 Yamaha AT1-B Specifications

            Model 1970 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 1970 Yamaha AT1-B Parts 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 Motorcycle & Trail Biking handbook 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 Parts Store is Located: CLICK HERE