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)




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 - 52.010mm 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 47.992mm, wear limit 47.962mm


Main Bearing oil clearance 0.020 - 0.070mm



Crankshaft Conrod journal 42.992mm, limit 42.962mm


Conrod Big end housing 46.000mm - 46.010mm 

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


Conrod bearing oil clearance 0.024mm - 0.070mm 


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 0.030 - 0.065mm (limit 0.12mm)


Piston Rings, 1st ring 1.5mm thick x 2.9mm depth, 2nd 1.5mm 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 steel firing rings 1.25mm thickness




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 (example cylinder head rebuild)

Inlet. 0.16-0.17mm

Exhaust 0.21-0.22mm


Valve clearances, checking when HOT operating temperature, (coolant temp minimum 80c)

Inlet 0.27mm (0.22 - 0.32 acceptable)

Exhaust 0.32mm (0.27 - 0.37 acceptable)




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 7-8psi

Boost pressure (solenoid controlled) 10.3 - 10.7 psi (0.71 - 0.73 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 - DENSO 195500-1610

295cc measured at GTti 2.55bar fuel pressure. (320cc at industry standard 3 bar)

High Impedance 12.5 - 13.5ohm

Batch Firing.




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)  6.8 - 7.0mm

Wear limit of friction, 0.3mm above rivets 

Friction disc weight, 0.72kg


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



Flywheel weight 6.4kg




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 Denso W22ETRL,  NGK BPR7EKN 

Replace 15,000 miles


Modern Iridium type spark plug upgrades...30,000 miles life



Denso IridiumTT  - IW20TT (Very long life)

Denso Iridium Power - IW20

Denso Iridium Power  -IW22


Conventional electrode type plugs also work perfectly OK and are cheap, but best replace every 6000-8000 miles.


NGK BP6ES, BP7ES (non resistor) or BPR6ES, BPR7ES (resistor)






Engine oil.

Use any modern quality latest rated API/ACEA. Fully synthetic or semi synthetic prefered but not essential if changes are regular.


Recommended oil 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.







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