1971 Yamaha Enduro HT1B 90cc Page

Welcome to the 1971 Yamaha HT1-B Forum. Feel free to post anything related to this model in the category. The Factory color was called Metallic Purple. The USA vin range was HT1-215101 to 229459 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.                

                     1971 Yamaha HT1-B Specifications

            Model 1971 Yamaha HT1B

   Dimensions:

Overall Length 73.8 In. / 1,875MM

Overall Width 35.4 In. / 900MM

Overall Height 40.7 In. / 1,035MM

Wheelbase 48 In. / 1,220MM

Min. Ground Clearance 8.9 In. / 225MM

    Weight:

Gross 201 Lbs. / 90Kg

Net 190 Lbs. / 90Kg

   Performance:

Max, Speed 55 MPH / 95Km/h

Fuel Consumption 164.5 MPG @ 25 MPH / 70Km @ 40Km/h

(On paved level roads)

Climbing Ability 25 Degree

Min. Turning Radius 68.9 In. / 1,750MM

Braking Distance 23 Ft. @ 22 MPH (7M @ 35Km/h)

   Engine:

Model HT1

Type 2 Stroke, Gasoline

Lubricating System Separate (Yamaha Autolube)

Cylinder Single, forward inclined 5 Port

Displacement 5.43 cu. in. (89cc)

Bore X Stroke 1.969 X 1.795 In. (50 X 45.6MM)

Compression Ratio 6.8:1

Max Power 8.5 BHP/7,000 RPM

Max Torque 6.51 Ft.-Lbs @ 6,500 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-7H 0.5-0.6 MM

Contact Break Point Gap 0.012 - 0.015 Inch / 0.30 - 0.4 MM

Fuse 10Amp X 2

Condenser Capacity .22UF (Microfarad)

   Carburetor:

Type VM20SC

Main Jet # 85

Jet Needle 4D3-3

Air Jet -

Needle Jet N - 6

Cut Away 2.0

Pilot Jet (#) 30

Air Screw (turns out) 1 3/4

Starter Jet (#) 40

Float Level 22.5MM

Idle Speed 1350 - 1450 RPM

  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 650 - 700cc / .69 - 0.79 Qts

   Gear Box:

Type Constant Mesh, 5 Speed Forward

1st Gear teeth & Ratio 3.182 (35/11) 43.373

2nd Gear teeth & Ratio 2.000 (30/15) 27.263

3rd Gear teeth & Ratio 1.368 (26/19) 18.653

4th Gear teeth & Ratio 1.000 (23/23) 13.631

5th Gear teeth & Ratio 0.800 (20/25) 10.905

Secondary reduction system Chain

Secondary reduction ratio 3.500 (49/14)

  Chassis:

Frame Tubular-Double Loop

Front Suspension System Front Telescopic fork

Rear Suspension System Swinging Arm

Fork Oil Capacity 132cc - 147cc (4.5 - 5.0 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 4.3 In. / 110MM

  Braking System:

Type of brake Internal Expansion

Front Operation System Right hand operation

Rear Operation System Right foot operation

  Tire Size:

Front 2.75 - 18 - 4PR Trials Universal

Rear 3.00 - 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 F130-07

Manufacturer Hitachi Ltd.

  Battery:

Model 6N2-2A-3

Manufacturer Furukawa Battery

Capacity 6V 2AH

  Lighting:

Head Light 6V 25W/25W

Tail Light 6V 5.3W

Stop Light 6V 17W

Meter Light 6V 3W X 2

High Beam Indicator Light 6V 1.5W

Flasher Light 6V 17W

  Tanks:

Gasoline Tank Capacity 1.7 Gallons (6.5 Liters)

Oil Tank Capacity 1.3 Quarts (1.2 Liters)

  Chain:

Tension (Up & down free play) 20MM (25/32)

The 1971 Yamaha HT1B Rider's Manual is Located: CLICK HERE

The 1971 Yamaha HT1B Service Manual located: CLICK HERE

The 1971 Yamaha HT1B Parts Manual Supplement is Located: CLICK HERE

The Primary HT1 Parts Manual is Located: CLICK HERE

The 1971 Yamaha HT1B Article is Located: CLICK HERE

The 1969-1971 Yamaha Autolube Adjustment & Color Codes are Located: CLICK HERE

The 1971 Yamaha HT1-B Brochure is Located: CLICK HERE

The 1971 Yamaha HT1-B Factory Dealership Poster is Located: CLICK HERE

1971 Yamaha Full Line Up Brochure: CLICK HERE

The 1971 USA Yamaha Enduro Line Up Brochure is Located: CLICK HERE

The Germany 1971 Yamaha Line Up Brochure is Located: CLICK HERE

The 1971 Yamaha HT1B Advertisement is Located: CLICK HERE

The 1971 Yamaha HT1B Store is Licated: CLICK HERE