Specifications and Data 

Commonly requested information is highlighted in Bold

Engine: CB-80 (worldwide market designation, Mostly non-Catalyst but a few countries had Catalyst version),

            CB-70 (JDM market, All Catalyst)

 

993cc.

 

Bore 76.00mm, (Wear limit 76.03mm)

 

Stroke 73.00mm

 

Compression Ratio 7.8:1

 

Cast iron block - Height 206mm.

 

Bore taper limit 0.10mm

 

Block Deck Surface max distortion 0.10mm

 

4x Main bearings, 52.000mm - 52.004mm main bearing housing.

 

Crankshaft Thrust Clearance 0.02 - 0.22mm (limit 0.30mm)

 

Crankshaft Width between thrust washer contact surfaces 23.130mm - 23.000mm

 

Crankshaft thrust washer thickness 1.990mm - 1.940mm

 

Crankshaft Width between crankpins 25.20mm - 25.00mm

 

Crankshaft maximum runout 0.06mm

 

Crankshaft Main bearing Journal 48.000mm, wear limit 47.976mm

(But I would advise regrind crankshaft if worn under 47.985)

 

Main Bearing oil clearance 0.020 - 0.044mm

 

Crankshaft Conrod journal 43.000mm, limit 42.976mm

(Advise regrind if worn under 42.985)

 

Conrod Big end housing 46.000mm - 46.008mm 

(vital to check this size and roundness if you have had a big end bearing failure)

 

Conrod bearing oil clearance 0.024mm - 0.048mm 

 

Conrod centre to centre length 125.00mm

 

Conrod small end for piston pin 19.00mm

 

Conrod small end width 22.00mm

 

Conrod Big end width 24.80mm - 24.85mm

 

Conrod Thrust clearance 0.15mm - 0.45mm

 

Conrod Weight 572g

 

 

 

 

 

Pistons. Flat top crown, semi forged (high pressure cast) with 1mm deep indents for inlet valves.  

Compression height 31.00mm

 

Piston to Cylinder clearance 0.045 - 0.065mm (limit 0.12mm)

 

Piston Rings, 1st ring 1.47mm thick x 2.9mm depth, 2nd 1.47mm x 3.15mm, Oil 2.8mm x 2.6mm

 

Ring gaps, 1st ring 0.35 - 0.45mm (limit 0.70), 2nd 0.28 - 0.40 (limit 0.70), Oil 0.20 - 0.70 (limit 1.1mm)

 

Side clearance 1st 0.05mm - 0.09mm, 2nd 0.02mm- 0.06mm, Oil 0.01 - 0.03mm

 

Piston Pin 19.00mm. Oil clearance piston pin to piston 0.03mm maximum

 

 

 

 

Flywheel weight 6.4kg

Flywheel step height (clutch cover mounting surface to flywheel friction surface) 23mm

Flywheel dimple for Ignition timing , 10 BTDC

 

 

 

Engine Valves.  

 

Inlet 107.0 length (limit 106.2mm), 30mm diameter. Stem 6.0mm 

Exhaust 107.2 length (limit 106.4mm), 26mm diameter, Stem 6.0mm

Valve seat recession. Inlet 4.23mm maximum, Exhaust 5.30mm maximum

Valve face seat angle 45.5 degrees.

Valve head minimum thickness. Inlet 0.7mm, Exhaust 0.8mm

Valve guide to valve stem oil clearance. Inlet 0.025mm - 0.08mm, Exhaust 0.030mm - 0.09mm

 

 

 

 

Cylinder Head height 119.00mm (useful to check how much a head has been previously skimmed)

 

Head Surface maximum distortion 0.10mm

 

Cylinder Head gasket - Composite graphite with stainless steel firing rings, 1.25 - 1.3mm thickness (when fitted)

 

 

 

Timing belt 1240mm length, 155 teeth, 19mm width, 8.0mm teeth pitch.

 

Number of belt teeth between pulley timing marks:

Inlet camshaft pulley to exhaust pulley, 44 teeth

Exhaust pulley to crankshaft pulley , 51 teeth

Crankshaft pulley to inlet camshaft,  60 teeth

 

 

 

Camshaft Journals 28.00mm

Camshaft bearing oil clearance 0.025mm - 0.066mm (Limit 0.16)

Camshaft Thrust clearance, 0.20mm maximum

Camshaft lift Inlet 7.60mm

Camshaft lift Exhaust 7.20mm

Camshaft Lobe height inlet 39.65mm - 39.55mm (limit 39.40mm)

Camshaft lobe height exhaust 39.25mm - 39.15mm (limit 39.00mm)

Camshaft Runout  0.03mm maximum

 

 

Valve adjusting shims 25.00mm diameter (some motorbikes also use this size)

Valve lifter 29.985mm - 29.975mm width

Valve lifter oil clearance 0.015mm - 0.046mm (limit 0.070mm)

 

 

 

Valve clearances for Cold engine adjustment setting (use when reconditioning cylinder head)

Inlet. 0.15 - 0.16mm

Exhaust 0.22 - 0.23mm 

 

Valve clearances at operating temperature, (coolant temp minimum 80c)

Inlet 0.27mm (+ Plus or - Minus 0.05mm)

Exhaust 0.32mm (+ Plus or - Minus 0.05mm)

 

 

 

Valve springs 45.9mm height, 21.1mm width. Length when fitted 35.0mm, load 23kg. 

Spring constant 2.1/2.72 kgf/mm

 

 

 

Turbocharger IHI RHB51, model VQ10 1987-1989,  VQ17 (Coolant cooled 1989-1993)

 

Compressor wheel 5/5 blades.  Inducer 31.5mm, Exducer 51mm

Turbine wheel 9 blades. Inducer 50.4mm,  Exducer 35mm

Turbine housing A/R  P12

Wastegate actuator starts moving 8psi

Boost pressure (solenoid controlled) 10.3 - 10.5 psi (0.71 - 0.725 bar)

Safety overboost cutout 12.7 - 13.1psi (0.87 - 0.9 bar) if exceeded for 0.8 second

Dashboard Boost indicator light on at 4 psi 

 

 

 

Fuel injectors 295cc measured at 2.5bar base fuel pressure. (325cc at industry standard 3 bar)

High Impedance 12.5 - 13.5ohm

 

 

 

Throttle body diameter 35mm (measured behind butterfly)

 

 

Clutch friction disc 180mm outer, 125mm inner. Woven Organic.

Made by Daikin-Exedy.

6 hub springs.

Friction disc thickness 3.0mm (flywheel side), 3.2mm (Pressure cover side),

Marcel spring metal thickness 0.55-0.65mm

 

Clutch disc thickness uncompressed 7.4 - 7.7mm

Disc thickness when fitted (marcel spring fully compressed flat)  6.75 - 6.85mm

Wear limit of friction, 0.3mm above rivets 

 

Disc weight 0.8kg

 

Clutch Pressure Cover factory fitted made by Daikin-Exedy.

Clamp load as fitted new 310kg.

Raising to peak of approx 380kg at optimum wear point.

Clutch cover weight 2.05kg

 

 

 

 

Spark plug cables,  standard type HT cable (7mm resistive carbon core) 

 

 

Spark plugs. Twin ground electrodes for longer service life.  Factory fit was Denso W20ETRL.

Gap is preset at 0.9 - 1.0mm and can't easily be adjusted. 

(CB70 Denso W20ETL same but non resistor)

 

NGK equivalent BPR6EKN (these have a 0.8mm gap)

 

Cooler heat range plug (recommended) Denso W22ETRL,  NGK BPR7EKN 

Replace 15,000-20,000 miles

 

Modern Iridium type spark plug upgrades... 

NGK BPR7EIX , lifespan about 40,000 miles 

Denso Iridium Power IW22 Lifespan about 25,000 miles

Denso Iridium Tough VW22 (probably last 50-60,000 miles or more!)

 

 

Conventional electrode type plugs also work perfectly OK and will only cost a few £pounds each., but best replace these every 5000-6000 miles,

 

NGK BP7ES (non resistor) or BPR7ES (resistor)

BOSCH W5DC (non resistor) or WR5DC+ (resistor)

 

 

 

 

Engine oil.

Use fully synthetic or semi synthetic.

Recommended grades 0w 40, 5w 40, 10w 40, 5w 50, 10w 50.

 

Total Capacity 3.3 litres, Oil change without changing filter 2.7 litres, With filter 3.1 litres.

 

NEVER ALLOW OIL LEVEL TO DROP DOWN FROM FULL ON DIPSTICK. ALWAYS KEEP IT FULL.

BIG END BEARING FAILURE SEEMS MORE COMMON WHEN OIL LEVEL HAS BEEN ALLOWED TO DROP, EVEN HALFWAY ON DIPSTICK IS RISKY.

 

 

 

Gearbox oil. 75w 85 or 75w 90. GL4 or synthetic GL4/5

Capacity 2.1 - 2.2 litres

 

 

Brake fluid. DOT 4, Super DOT 4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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© Nathan Munns