Honda CB 400A Hondamatic


Make Model

Honda CB 400A Hondamatic




Air cooled, parallel twin cylinder, SOHC, 3 valve per cylinder


Bore x Stroke 70.5 x 50.6mm
Compression Ratio 9.3:1


2x 32mm Keihin carbs

Ignition  /  Starting

CDI  /

Max Power

26,8 HP @ 8000 rpm

Max Torque

21,39 lb/ft @ 5000 rpm

Transmission  /  Drive

2 Speed automatic

Front Suspension

Telescopic forks

Rear Suspension

Dual EVO dampers with 5-way spring preload adjustment.

Front Brakes

Single 282mm disc

Rear Brakes

153mm Drum

Front Tyre

3.60 S19

Rear Tyre

4.10 S18


177 kg

Fuel Capacity 

13 Litres

Automatic transmissions may seem somewhat unnecessary on motor cycles, but they are very popular in the United States and, as theirs is such a large market, it dictates that more should be made. The Honda 400 Auto is unique in that it is the first of the new-generation autos as a middleweight roadster rather than superbike, like the 1000cc Convert Guzzi and 750 Hondamatic.

The 400 is the CB400 Dream and, like the manual version, is a four-stroke, twin-cylinder machine. The Auto's engine differs in tune from the manual and has 3obhp at 8ooorpm compared to 43bhp at o,5oorpm. Torque is down just a little to 20.251b ft at 6000, which is 2ooorpm lower down the rev range than its sister bike and much more useful for its semi-automatic gearbox which has just two gears. The modifications are by way of smaller carburettors, smaller ports and milder camshaft. The three-valves per-cylinder (two inlet, one exhaust) twin with chain-driven contra-rotating balance shafts in auto guise is a very smooth and well-mannered machine indeed, even if performance is riot a strong point.

The bike's gearbox is not truly automatic in the car sense, being a two speed unit with torque converter

 and manual change. First gear is for up to 5omph, while second will take the machine to its top speed of o,5mph.

Riding the 400 requires a new technique. The bike will only start if the gear selector is in neutral and the gearchange order is neutral at the bottom, with the two gears 'up', second above first. Should you forget to take the bike out of gear and put the side stand down, a failsafe switch will cut-out the ignition, thus preventing the bike from taking off without the rider.

The bike works remarkably well if just left in the higher of its two ratios and will pull away, albeit fairly slowly, from second gear. As can be expected, even using both gears, acceleration is not startling, with a standing start quarter mile time of 17.2 sees. Fuel consumption is good, however, and can average out at just on 6ompg.

With the exception of the gear-position indicator replacing the unnecessary tachometer, and a parking brake replacing the clutch lever, the CB400 Auto is just like the pre-Super Dream manual version with its 'Americanised' styling and attractive Comstar wheels.

Motorcycle Mechanics review 1980

LET'S GET clear right from the start. The 400cc Hondamatic is not an automatic gearbox motorcycle. The gearbox is quite conventional in that it has a mechanical foot change, but only incorporating two speeds. What makes it a Hondamatic is the fluid flywheel coupling the engine to the gearbox.

Like any other machine the engine is started in neutral, but you lift the pedal to obtain either of the two gears. The left hand, "clutch" lever is a parking brake and is fitted with a lock-out device so that you can't pull it on when riding. Pulling away for the first time is a strange experience, using the first, low, ratio initial take off is very quick because all you have to do is snap the throttle open. However the flywheel slips for quite a time and first gear can be used up to an indicated 55/60mph if the engine is screamed quite hard. With no tacho fitted you have to play the engine revs by ear.

For normal riding I found it best to change up at around 30mph although the higher ratio can be retained at speeds well below this. Once you get used to the bike you get quite lazy and on a couple of occasions I found myself pulling away in high gear! The motor and flywheel can cope with this quite well but performance isn't exactly shattering.
Neutral is very easy to select since it is at the bottom of the pile. From top gear you just press the pedal down twice. This can lead to problems because in a tight situation you stop thinking Hondamatic and revert to normal bike riding actions. Approaching a corneror a roundabout you might change down once and then need a bit of extra power to accelerate out of trouble, down goes the gear pedal once more and you find yourself with a high revving engine and no more forward motion at all!

Cornering with the Hondamatic is quite deceptive. Initially you tend to go around with very little throttle, almost free-wheeling. The technique is to use the lower ratio and power the bike through the turn. You have to crack the throttle early though, because the drive takes a fraction of a second to reach the back wheel. Once you get the hang of it the footrest can be touched down and the bike still feels quite steady.

Engine breaking is another area that needs to be re-learned, sometimes you have it and other times you don't! In high ratio you can cruise at 70mph and just ease back the throttle to lose speed. However, once the speedo drops to around 50mph you start to free-wheel. Dropping down to low ratio gives you engine braking once more until the road speed drops to about 10to 15mph.
With the "now you see me, now you don't" engine braking you have to rely a little more on the bike's brakes, the single disc on our test model was just about up to the job.

The lever lacked some feel and I got the impression that the pads weren't quite fully bedded in. The twin discs of the 400N would have been nice although a lot of riders would have then found the bike overbraked. I assume the 250N set up is used because the bike only delivers 250cc performance.

The standing quarter times and the top speed are about par for the current 250cc state of the art. Getting the bike off the line for the standing start times was a piece of cake. There was no need to experiment with different engine speeds and throttle settings to get the best take-off. All you have to do is plant your right boot firmly on the back brake pedal and give it full throttle. When you want to go you just release the back brake.

Top speed might have improved, given a couple of miles run up to the lights, but with the Hondamatic such things are academic. The bike will hold a very relaxed and comfortable 70mph all day and the riding position is just about right as a touring/commuter compromise.

With the bike averaging around 55mpg the fuel tank could have been larger. The range to reserve varied from 90 to 110 miles. With the elastic type connection between the engine and the gearbox, fuel consumption is bound to be higher than with a conventional transmission. On the other hand you have a 400cc engine producing 250 type performance which means that the motor is hardly being stretched at all. Some might argue that a 400 ought to go quicker, but judging from some of the dealers' discount prices you are getting the bike at around the cost of the better two-hundreds.

Not having to worry about the clutch leaves you free to concentrate on the throttle operation and this, combined with the clean snatch-free pick up, makes the bike a first class traffic machine. You can trickle along at slower than walking speeds and maintain perfect balance. In the London rush-hour it is the easiest bike to control that I have ever ridden.

As far as I can make out the only real black mark is the slightly high fuel consumption. If you ignore the capacity of the engine, performance is more than adequate for commuting or touring and the price, discounted that is, makes the bike a real bargain. So why have Honda taken two years to get a road test bike to us? Have they been hiding their light under a bushel — or is there a long-term reliability catch? Only time will tell.

Source Motorcycle Mechanics review 1980