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.

                    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 Australia 1970 Yamaha AT1F-E Parts Manual is located: CLICK HERE

The 1970 Yamaha AT1B Owner's Warranty Card 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

1970 Yamaha AT1B Parts CLICK HERE