The engine of the Honda Cb Bol d' or.


A multi-purpose engine has great elasticity


The inline four-cylinder engine with double overhead camshaft were produced in three different capacities: 750, 900 and 1100. Appeared on the market in 1978 were equipped with various versions of motorcycles until 1984.


Motore cb

Among the three, the more balanced and more interesting with the performance, the engine is 900 cc engine, although it was made after 750 and is modeled on the geometry, the engine is very different especially in the bore / stroke ratio, the fact 750 is an engine part (62x62 mm) and 900 (64.5 x69 mm) is a long-stroke engine. Also inherits the fluid dynamics of the prestigious CBX1000 six-cylinder for which combustion chambers, valves and pistons (same) were the result of a lengthy study.

The engine has two camshafts in the head, which operate four valves per cylinder acting directly, thus without barbells on break pads inserted in the appropriate glasses that act directly on the valves.

The motion is transmitted to the camshafts by two chains: one takes the motion from the motor centrally and forward it to the exhaust shaft, the other connects the tree with the suction drain.

The four valves per cylinder provide a number of obvious advantages such as higher speeds, better coverage at high speeds, placing the candle in a central position in the chamber.

The maximum power (95 hp at 9000 rpm), especially when compared to most modern engines, could suggest an engine obsolete, but it is not. To better understand why some considerations should be made.

The power of the engine depends on two variables, torque and speed and, in terms of horses, is given by the formula: Power (hp) = Torque (kgm) RPM: 716.2.

The couple is the 'moment of force' on the motor torque generated by the combustion pressure exerts on the piston is therefore closely related to the amount of air-fuel mixture entering the cylinder and depends mainly on the displacement.

At the same airspace, the maximum torque can not be very different from one engine to another, to achieve high specific power must increase the speed at which the engine deliver the maximum torque, taking it almost coincides with the regime of maximum power.

In this way, but the engine will have a good efficiency only to a very high speed, while it will be very powerful at low and medium engine speeds.

Conversely, the motor of the CB 900 is a versatile engine that is expressed with dignity at all speeds.

In fact, the arrangement made with an engine, as well as the timing of the distribution is determined decisively by the efficient filling and emptying of the chamber and then dall'accordatura waves of pressure and vacuum that is created in the intake and unloading. Mainly affects the tuning of aspiration in which there are, for this engine, although conflicting effective optimizations.

The ducts closer and / or long (must be taken into account, however, all the way that leads air into the combustion chamber, including the diameter and number of valves) lowers the resonant frequency, and give a greater acceleration of fluid at low rpm.

4 valves per cylinder, given the reduced bore, are quite narrow and the overall diameter of the ducts is suited to medium-high schemes rather than high.

In contrast, the venturi carburetors are fairly large and reduce the difficulty of breathing at high rpm, the spark plug center frontefiamma reduces the already short for boring and ultimately reduced the valves smaller and more difficult to read at high speeds, ensuring flicker so a good extension.

The improved cylinder filling, and the resulting torque, schemes are quite high, however this does not affect the shot since the very low speed thanks to the very long run and all 'large lever handle that is typical of two cylinders of equal capacity but is expressed with the fluidity and the vibrations of a far more balanced four-cylinder.

In conclusion, we have a multi-purpose engine, has great elasticity, and then with only five well-spaced gears. In fact, it excels in the data of maximum torque and power (and then under specific conditions) because it is extremely generous to the average values ​​(learning speed), giving a recovery / acceleration more than satisfactory.

E 'in practice as having three engine displacement of less involved one at a time when the time comes, one optimized for bass, one for the medium and the third for high speeds.

by Barracuda and Paper

by Duck and Barracuda




Dati Tecnici Principali


  CB750 K CB750 F CB900 F CB1100 F
Cilindrata (cc)
Alesaggio corsa (mm)
Potenza all’albero (CV-giri)
77 a 9000
80 a 9000
95 a 9000
100 a 8500
Potenza alla ruota (CV-giri)
68 a 9000
69 a 9000
80 a 9000
94 a 8500
Coppia massima (Kgm-giri)
6,9 a 7600
6,5 a 8000
7,9 a 8000
9,4 a 7500
Velocità massima (Km/h)
400 m da fermo (sec)
Peso a vuoto (Kg)


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