Built around well-established Japanese thinking the Honda CB400-four offers few surprises. Using a plain bearing crankshaft and single overhead cam, the baby four is a scaled down version of the CB750 that had already been around for some 7 years by the time of the 400’s introduction. Honda did slip up however and failed, as they so often have done, to create the perfect machine; the cam chain tensioner is a ludicrously complex device, using several non-conventional methods to take up the slack in this all important engine component. The result is an often-noisy engine and, more importantly, stripped cam adjuster threads, as owners repeatedly try to adjust the bolt, and lock nut, at the front of the engine, attempting to quieten down the chain as it slaps its way around the internals.
This malady aside however and the CB400-four is generally a delight to be with, worldwide over 105,000 units were produced with over 15,000 of those finding there way into the UK market between 1975 and the types demise in 1979, by comparison the US sold around 1000 units less than the UK total during this period, proving a great disappointment for Honda in the states. In more modern times the CB is a real restorers delight, with most parts still available and at reasonable cost too, as an added bonus and with little difference between the models, there is a plentiful supply of used parts out there too. David Silver, the leading independent Honda part supplier, saw this coming many a year ago and began sourcing parts no longer available through Honda from the original suppliers. Mechanically, and cam chain tensioner apart, there is little to go wrong with the engine, which should be good for 100,000 miles when serviced regularly. There are reports of a few leaking head gaskets in earlier models but most will have been ironed out long ago. Japanese chrome, now three decades old, is unlikely to have survived intact unless great care has been taken in its well-being, the front and rear mudguard simply rotting away if left unkempt. The same can be said for the front brake caliper that will seize up on its pivot points at the mere whiff of road salt. Even so, this is 70’s biking at it best and the 400/Four simply oozes character, cost effective to run, easy to maintain and even easier to ride to great effect, it is no wonder the UK biker took this little bike to their hearts. That feeling is still strong and wherever a 400-Four is stood bikers of a certain age will stop and pass comment, all having a story of either personal ownership or a mate that had one. Yamaha may have sold more RD’s in the period but few two-stroke owners will look back on their past with the same affection as a Honda jockey does, that feeling of a connection between bike and rider is never stronger than with the 400-Four.
This diminutive bike is full of surprises. Nimble, and fast too, especially in its hunting ground of sweeping B roads, the little Honda rewards the expert rider while complementing those not so good. From the first prod of the starter button, the feeling is one of totally competency, the engine quickly settling into a relaxed smooth tickover with a quick reaction to throttle inputs making the inline four come alive. With its steering just on the fast side of stable, the Honda makes the most of its limited chassis capabilities, never having enough power to truly upset the apple cart but still possessing more than enough speed to do the job with a stunning capability. If it has an Achilles heel then the pair of rear shocks is the culprit, Japanese handling was still very much in its infancy and Honda had only just started to design frames as a part of the whole package rather than a bracket that simply holds the plot together and it shows. The frame and forks are virtually identical to the type used on the CB250 and 350 twins from the same period, but somehow in this machine they do seem to work just that bit better, and with more confidence with just the rear end lagging behind its mates up front when it comes to dancing with some accuracy.
Once up rated with aftermarket dampers, the ride gets considerably more predictable, proving the simple frame design to be an effective one. In standard form the front brake with its single floating-caliper borrowed from existing designs from the big H, is less than adequate, after market brake pads or even later versions produced by Honda do pep this system up considerably The seating position is more perched on than actually sat in but the combination of a semi rear set footrest position and narrow bars make for a comfortable ride allowing the rider to remain in the saddle for long periods.
Despite the sporting pretensions and willingness to rev when at a standstill, the 400-Four never feels like it is ever in a hurry, this slight of hand is attributable to the engine that never feels buzzy or indeed busy. If anything the power plant feels to be flat and disinterested, particularly in the mid range, the smooth four needing a heavy throttle hand to get the most out of it. Riding the CB400-four to great effect is a lesson in keeping going, with a standing quarter around the 15-second mark it is never going to win any drag races from bend to bend so, it’s a case of high corner speeds and maintaining momentum at all cost. With the taps fully opened the tacho can be allowed a full sweep across into the five-figure rev range, where it will happily go of course. Up around the dusty end of the tacho dial the Honda comes alive; the exhaust note hardens, although the overall feel of the engine never does, proving, as many a talented tuner has found out, that the tough inline-four engine is capable of much, much more in the right hands. The engine has found its way in to many a racer where its longevity under pressure really comes into its own.
Honda CB400-4 Model history
First seen in 1975, and little more than a development of the existing CB350, albeit a model never sold into the UK, the 400-Four established several design pointers that would hang around for a good few years after its launch. The clean European styling setting the trend for the rest of the decade and beyond with hints still emerging in modern machines thirty years on. An all-new, six-speed, gearbox provided the transmission while the tank and seat arrangement kept the overall look both a racy, and a modern one.
The iconic, four-into-one, exhaust is actually the result of mechanical necessity rather than styling genius, the Honda engine layout necessitated the oil filter to protrude at the very front of the casings which, in turn, meant the four down pipes had to side swerve to enable service access to this consumable item. The end result still stands as one of the finest bits of chrome work ever seen on a motorcycle, many feeling the design wouldn’t look out of place as furniture or pure art either.
When the baby four finally arrived in the dealers showrooms it was popular, despite being the most expensive lightweight machine in its capacity class, even so it is reputed that Honda lost money with every one they sold, there being little difference in construction costs to a larger capacity and far more profitable 750cc machine. The type was never a hit stateside either despite many attempts at kick starting its career on the other side of the pond. None the less the CB400-Four sold well in its day, effectively putting Honda on the UK map once and for all and still attracts more than a strong interest being one of the few machine from the 70’s that parts can still be readily, and more importantly, affordably bought for. The machines that followed the 400-four lacked all of the character and appeal set out by the earlier design. The 400cc twin Superdream, although an effective machine in its own right, and on the road more than a match for the inline four, never really captured the imagination, never achieving iconic status and as such has all but disappeared in the mists of time.
Honda CB400-4 Timeline
1975 – Chassis number CB400F-1007709
First seen in red or blue with matt black side panels the ground breaking CB400/four was an instant hit even at £669.
1976 – Chassis number CB400F-1010771
No major changes to the machine with the exception of the pillion pegs that were removed from the swing arm and bolted onto loops attached to the frame.
1977 – Chassis number CB400F-1048301
Once again no major mechanical improvement, a locking filler cap was added however. Longer cylinder studs were implemented as leaking head gaskets were a common problem.
1978 – Chassis number CB400F-1074740
The F2 model was launched (often prompting people to mistakenly call the earlier model the F1) little more than cosmetic changes marked the arrival of this new machine the most noticeable was the repositioning of the filler cap from the centre of the tank to an recessed, offset position.
Honda CB400/4 Specifications
- Engine – air-cooled 4-cylinder 4-stroke SOHC
- Capacity – 408cc
- Bore/stroke – 51x 50mm
- Power – 37bhp @ 8500rpm
- Torque – 24ft-lb @ 7500rpm
- Carburetion – 4 x 20mm Keihins
- Transmission – 6-speed wet clutch chain final drive
- Frame – steel cradle
- Suspension – 33mm telescopic forks. Twin shock rear
- Brakes – 267 mm disc single piston floating caliper, 160 mm single leading shoe drum
- Wheels – 300 x 18, 3.50 x 18
- Weight – 170kgs
- Top speed – 102mph
- Wheelbase – 1359mm
- Fuel capacity – 14ltrs
Honda CB400 Four Gallery
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