Air right this moment, gone tomorrow: One final hurrah for Honda CB1100 as air-cooled fours look prepared for retirement


1 of 5

Despite the straightforward proven fact that Nineteen Seventies-styled bikes are in vogue on the second with manufacturers scrambling to revive tools from their pasts, a single of essentially the most convincing of these retro designs is on the best way out – and utilizing with it an iconic engine configuration that’s unlikely at any time to return.

Related content material on MCN

Honda have found {that a} ‘Last Version’ of the CB1100 will debut shortly in Japan, and since the gadget doesn’t fulfill Euro5 emissions rules, with no instant substitute on the horizon, it is usually established to vanish from showrooms on this facet of the earth.

Derogation guidelines, enabling time to supply leftover non-compliant fashions, point out Honda can preserve promoting it till lastly the conclusion of 2022 if there are enough remaining in inventory, however instantly after that – or earlier than if shares function out – it should flip into tough to purchase a model new air-cooled four-cylinder bike.

Air right this moment, gone tomorrow: One final hurrah for Honda CB1100 as air-cooled fours look prepared for retirement

It’s unimaginable that these sorts of a machine has managed to cling on this prolonged. With the CB1100, Honda invested in radical, patented air-cooling applied sciences to beat the emissions legal guidelines in put when it was launched in 2010, when different manufacturers had beforehand deserted the plan of air-cooled inline fours.

Now even that innovation just isn’t ample to proceed being abreast of air air pollution guidelines, and with the ready cease for inside combustion engines beforehand showing on authorities schedules all-around the globe, no agency will plough the demanded exertion in to revive the air-cooled 4 configuration.

Introduced that some air-cooled engines have managed to endure and prosper exterior of the date that a number of thought emissions tips would eliminate them – BMW’s R1800 choice, for event – why are fours such a problem?

The reply is that though singles, V-twins or boxer twins have their cylinders uncovered to the motion of cooling air on all sides, and even the cylinders of parallel twins can have quite a lot of airflow throughout them, the middle two cylinders of an inline 4 (or the centre cylinder of an inline triple) are surrounded by the heat generated by combustion within the different two cylinders.

Air right this moment, gone tomorrow: One final hurrah for Honda CB1100 as air-cooled fours look prepared for retirement




Which means the outer cylinders, with air hurrying earlier them, might be saved cooler than the middle varieties, and any imbalance in temperature like that triggers complications when it should come to managing emissions.

Heat isn’t the dilemma, however the lack of ability to administration it’s. Water-cooling, with channels in between the cylinders and through the cylinder head, often means engines might be warmed up quickly – essential for emissions exams that embrace issues like chilly begin off-up measurements – after which saved at a steady temperature many because of the thermostat controlling consuming water circulation by means of the bike’s radiator.

On an air-cooled motor you simply can’t do this, and as temperatures alter the assets within the cylinder, pistons, piston rings, valves and heads will broaden and deal.

Broader tolerances are wished to battle that growth, creating emissions handle even more durable, and if – and on an inline 4 – the middle cylinders are hotter than the outer ones, retaining your complete engine within the candy location for low emissions turns into much more sturdy.

Might it’s completed? Nearly definitely. However offered the deficiency of evident rewards other than the aesthetics, it’s robust to visualise any agency producing that expense yet again. It could possibly be on the best way out, however right here’s how the CB1100 managed to present air-cooled fours a ten years of additional on a regular basis dwelling.

Air right this moment, gone tomorrow: One final hurrah for Honda CB1100 as air-cooled fours look prepared for retirement

Oil cooling

The lubricating oil doubles as a cooling process. When popping out of the oil cooler, at its coldest, the oil pipes go straight to the cylinder head. The CB1100 has a further oil pump purely for cooling and a thermostat to bypass the approach when chilly.

Swiss cheese engine

The essence of Honda’s achievement in producing the CB1100 was permitting air to circulation by means of the motor as correctly as round it. Between people fins it’s like 4 specific particular person cylinders, enabling air to function amongst them the place the most effective temperatures come up.

Cylinder head airflow

In addition to functioning among the many cylinders, the cooling air is directed up on account of the cylinder head, by means of channels everywhere in the combustion chambers and spark plugs to much more command their temperatures.

Air right this moment, gone tomorrow: One final hurrah for Honda CB1100 as air-cooled fours look prepared for retirement




A very long time of improvement

Though the CB1100 went on sale in 2010, it was demonstrated as a in shut proximity to-generation precept once more in 2007 (along with the delectable, however by no means ever-manufactured, CB1100R). Even at that part, Honda’s designers had by now set yrs of labor into its 1140cc air-cooled 4.

Potential compromises

Whereas the air-cooled 4 is bowing out, firms are having improved at preserving the ‘air-cooled’ glimpse. No matter whether or not it’s through the use of partial consuming water-cooling (consuming water-cooled heads on air-cooled cylinders) or hidden radiators and dummy fins, bikes evoking air-cooled designs will probably be with us for a although.