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Welcome to the 1971 Yamaha HT1B-MX Forum. Feel free to post anything related to this model in the category. The factory color was called Competition Yellow. The USA Vin range was HT1-000101 to 023405. 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 HT1B-MX Specifications
Model 1971 Yamaha HT1B-MX
Dimensions:
Overall Length 73.4 In. / 1,864MM
Overall Width 35.4 In. / 900MM
Overall Height 40.9 In. / 1,038MM
Wheelbase 48.4 In. / 1,229MM
Min. Ground Clearance 9.1 In. / 231MM
Weight:
Gross 192 Lbs. / 87Kg
Net 181 Lbs. / 82Kg
Performance:
Max, Speed 55 MPH / 95Km/h
Fuel Consumption 164.5 MPG @ 25 MPH / 70Km @ 40Km/h
(On paved level roads)
Climbing Ability 32 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 8.1:1
Max Power 14 BHP/9,500 RPM
Max Torque 7.96 Ft.-Lbs @ 9,000 RPM
Piston Skirt Clearance .0016 - .0018 In. / 0.40 - 0.45MM
Starting System Primary-Coupled Kick
Ignition Timing B.T.D.C 2.5MM
NGK Spark Plug & Gap B9-EN 0.5 MM
Contact Break Point Gap 0.012 - 0.015 Inch / 0.30 - 0.4 MM
Piston Ring End Gap 0.15 - 0.35 mm (single ring)
Condenser Capacity .22UF (Microfarad)
Carburetor:
Type / ID VM24SH / 276 MI
Main Jet # 130
Jet Needle 4DH7 - 2
Air Jet -
Needle Jet N - 8
Cut Away 2.0
Pilot Jet (#) 30 / 0.6
Air Screw (turns out) 1 1/4
Starter Jet (#) 40
Float Level 22.5MM
Valve Seat 2.0
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 2.833 (34/12)
2nd Gear teeth & Ratio 1.875 (30/16)
3rd Gear teeth & Ratio 1.368 (26/19)
4th Gear teeth & Ratio 1.090 (24/22)
5th Gear teeth & Ratio 0.956 (22/23)
Secondary reduction system Chain
Secondary reduction ratio 3.714 (52/14)
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 4.5 In. / 114MM
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 Knobby
Rear 3.25 - 18 - 4PR Knobby
Front Tire Pressure 14 P.S.I / 1.0KG/cm2
Rear Tire Pressure 17 P.S.I / 1.2KG/cm2
Oil Pump:
Adjustment Stroke Min 0.20 - 0.25 MM
Adjustment Stroke Max 1.85 - 2.05 MM
Mix Ratio With & Without Pump 30:1 / 15:1
Dynamo:
Model F130-04
Manufacturer Hitachi Ltd.
Battery:
Model -
Manufacturer -
Capacity -
Lighting:
Head Light -
Tail Light -
Stop Light -
Meter Light -
High Beam Indicator Light -
Flasher Light -
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)
Wanted 1971 Yamaha HT1-MX Rider's Manual. If you have this manual for sale, or wish to donate a copy, we want this manual, for the digital library.
The 1971 Yamaha HT1BMX Service Manual Supplement is Located: CLICK HERE
The 1971 Yamaha HT1 Primary Service Manual located: CLICK HERE
The 1971 Yamaha HT1BMX 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-BMX Brochure is Located: CLICK HERE
1971 Yamaha Full Line Up Brochure: CLICK HERE
The 1971 Yamaha HT1BMX Store is Licated: CLICK HERE
