This is the home of the CB750-K0 the black widow build


1970 K0 The Black Widow

CB750 K0: 1969 – 1970

Production Dates1969-1970 Black Widow 5-1970 production date. Rebuild dates 11-2019 – 4-2020 proposed
Production Numbers53,400 (sand-cast 7,400)
Starting Frame#1000001 Black Widow 10368XX
Starting Engine#E1000001 Black Widow E10366XX
ColorsCandy Blue Green for for this build.
FeaturesTank, side covers, fork uppers and headlight shell were painted the same color. The throttle linkage used separate cables to each carb. All carbs fully rebuilt.
New wheel bearing front and rear along with seals. Also new Honda DID rims and tires Dunlop K87 rear Dunlop F11 front. Real axle and axle nut re-chromed.
Rechromed original K0 front fender, new speedometer cable and new front caliper along with new front brake pads.
The original front caliper arm was disassembled service with new seals and reattached.
All new exterior engine seals all side covers and valve cover were polished, and the oil pump rebuilt with new seals o-rings.
New, main wiring harness new points harness, new oil temp harness new headlight harness new safety switch harness, new dynamo harness and connector.
New rear shocks and rebuild front forks with new fork tube and new Honda fork seals, fork oil used Honda. New compression washers in front fork drain and lower leg attachment.
New low profile crash bars.
New front caliper, new brake lines with new compression washers, new front brake pads and rear brake shoes.
Triple tree rebuilt with new tapered roller bearings and seals not ball bearings.
New handlebar switches.
Rechromed original kick start arm and rechromed original starter motor cover.
New points cover from Honda.
New points, and condensers along with new NGK D-8ES spark plugs.
New clutch cable Honda.
Rechromed original clutch plate cover.
Rechromed original brake arm.
New HM300 exhaust with baffles Honda.
New center stand spring and kick stand spring both Honda.
New foot peg rubbers front and rear Honda.
New fuel lines, new drain and vacuum lines.
Rechromed original K0 rear fender

Overall length85.0 in.2,160 mm
Overall width34.8 in.885 mm
Overall height45.5 in.1,155 mm
Wheel base57.3 in1,455 mm
Seat height31.5 in.800 mm
Foot Peg Height12.2 in.310 mm
Ground Clearance5.5 in.160 mm
Curb weight517.3 lb235 kg
Weight distribution L/R271.1/209.5 lb123/205 kg
Frame & Suspension
TypeDouble cradle tubular steel
Front SuspensionTelescopic fork, travel 5.6 in., 143mm
Rear SuspensionSwing arm, travel 3.3 in., 85mm
Front Tire Size, Type3.25-19 (4PR) Rib tire, tire air pressure 2.0 kg/cm2, 28 psi 111577 Dunlop F11
Rear Tire Size, Type4.00-18 (4 PR) Block tire, tire air pressure 2.0 kg/cm2, 28 psi) 122371 Dunlop K87
Front BrakeDisk brake, lining area 2.9in2x2, 19cm2x2
Rear BrakeInternal expanding shoe, lining area 8.2in2x2, 53cm2x2
Fuel Capacity4.7 US gal, 3.9 Imp. gal18 liter
Fuel Reserve Capacity1.3 US gal, 1.1 Imp. gal5 liter
Caster Angle63º
Trail Length3.74 in.95mm
Front Fork oil capacity7.0-7.3 oz220-230 cc
TypeAir-cooled, 4-stroke, O.H.C. engine
Cylinder Arrangement4-cylinder in line
Bore and Stroke2.401×2.408 in.61×63 mm
Displacement44.93 cu in736 cc
Compression Ratio9.0
Maximum Horsepower67 BHP@8,000 rpm
Maximum Torque44.12 lb-ft@7,000 rpm6.1 kg-m@7,000 rpm
Carburetor, Venturi Dia.4x28mm Keihin, slide type
Valve trainChain driven overhead camshaft
Oil Capacity7.39 US pt, 6.16 Imp. pt3.5 liter
Oil Tank Capacity4.22 US pt., 3.55 Imp. pt2 liter
Lubrication SystemForced pressure and dry sump
Air filtrationPaper element
Valve Tappet ClearanceIntake: 0.002in./0.05mmExhaust: 0.003in./0.08mm
Engine weight (Wet)176.3 lb80 kg
Air screw opening1 1/8 turn
Idle speed900 rpm
Main jet#120
Idle jet#40
Air jet#100
Carb main bore1.102in.28mm
Drive Train
ClutchWet, multi-plate
Transmission5-speed, constant mesh
Gear Ratio I2.500:1
Gear Ratio II1.708:1
Gear Ratio III1.333:1
Gear Ratio IV1.097:1
Gear Ratio V0.939:1
Primary reduction1.708:1
Secondary reduction1.167:1
Final Reduction2.667:1 (17T x 46T)

Type12v, negative earth
IgnitionCoil and contact breaker, spare spark
Starting systemElectrical motor and kick start
Alternator3-phase 12 V 0.21kW@5,000 rpm
Battery Capacity12V – 14 amp hour
Spark plugNGK D-8ES
Spark plug gap0.024 ~ 0.028 in.0.6 ~ 0.7 mm
Points gap0.012 ~ 0.016 in.0.3 ~ 0.4 mm
Personal Cost:
I’ve been bitten by a Black Widow Spider during this build. I have also dislocated my left shoulder working on this project it’s better now. I’ve also suffered numerous cuts and scrapes during this build more than normal. After picking this ratted out CB750 K0 outside of Reno my car eat its power steering pump in Missouri. I’ve been forced to wait all day to sign for international packages on many occasions during this build. Tire’s from Japan, gauges from Europe, parts from Canada, and lot’s of parts from Japan. This is one of the last barn finds to be fully restored.
The Black Widow as purchased