HONDA CB400 F
The CB400 Four is a little jewel of a motorcycle,produced in the Café racer style from 1975 to 1977. Its single overhead-cam inline-four engine is a conventional, two-valve per cylinder design, but the small dimensions of the engine internals allow it to rev to a dizzy-for-the-time 11000rpm.
The 408cc engine was developed from the CB350F powerplant, which had been rather underpowered for many riders. Though n ot an overly powerful motorcycle, the CB400's 28kW (37bhp), combined with a 178kg (3921b) dry weight, gives the little 400 exceptional performance for its capacity. The motor was extremely smooth, as well as willing, and was fairly reliable, although its high-rewing nature occasionally caused piston-ring wear. Screw and locknut valve adjustment and points ignition meant regular maintenance was required for optimal running.
Chassis technology in the mid-1970s was more than up to dealing with the little 400, a conventional telescopic front fork and twin-shock rear suspension offering plush damping. Although the steel-tube double cradle frame now looks rather spindly, it was just about stiff enough for good handling. A single front brake disc and a single-leading-shoe rear drum brake allowed reliable stopping, and starting was by electric button and kickstart.
But is was the CB400's styling that won many fans, particularly the serpentine chromed downpipes of the four-into-one exhaust, which culminate in a glorious chrome collector box and megaphone silencer. A slabby fuel tank holds just 14 litres, but the CB400's meagre fuel consumption means this will still carry the rider past 240km (150 miles) between fuel stops.
Although the CB400 Four was a successful design, it was soon replaced by cheaper, less impressive parallel twin machines, such as the three-valves per cylinder CB400 Dream and later Super Dream. However, these designs did not have the style, panache or performance of the little 400 Four.
Road Test Cycle World 1974
After putting 2000 varied miles on the test CB400F Honda, our lasting and final impression of the machine at the conclusion of the evaluation was just the same as it had been at the beginning. And that isn't the way it always works. Sometimes a bike will please our riders initially, then expose its annoying peculiarities as the miles add up. The midsized Honda Four displayed a strong personality the first time we pressed the starter button, and maintained its charisma from that point on.
The 400F was born of the one-time-around CB350F, a bike that was to be admired for its four tiny cylinders, but not much else. A Honda technical exercise… yes. An exciting, pleasurable motorcycle… not really. Yet it offered enough to make us look ahead and imagine what it could be like, and Honda, reading the motorcycling public's mind as usual, gave us what we were after.
Tacking new sheet metal on the 350 Four wouldn't be all it would take to up the 350's performance image. Far more was required, and far more was delivered. Honda began with the engine. The 47mm x 50mm undersquare engine got a bore enlargement to 51 mm, for a total displacement of 480cc. The old cylinder head was dispensed with and a new design with far larger intake and exhaust valves—housed in more combustion chamber area—took its place. Crankshaft and connecting rods remain 350 style, as do the camshaft and four 20mm Keihin carburetors.
If you're after a sporty image, you might as well go all the way, and Honda did. The 408 engine cases are new, necessitated by a larger gearbox with six speeds instead of five. Some ratio changing was accomplished with the second, third and fourth gears, but first and fifth remain the same as on the old 350. The more powerful 408cc unit handles the taller sixth gear ratio with no trouble.
More shifting and extra power are probably the reasons behind the new clutch, which has different friction material and stronger springs to hedge problems. The clutch on our test machine required only one adjustment at the lever during many abusive runs at the drag strip, where our 400F reeled off consistent and strong 14.1-sec. quarter-mile times.
On the line, the 400's engine would be revved to its 10,000-rpm redline with the bike in first gear, the rider's weight would be rearward on the seat, and the clutch lever would be dumped against its stop with a bang. The mid-sized Four would then howl the rear tire with a wisp of smoke and the front wheel would skim through first gear about four inches off the deck until second gear was hooked up. To say that the 408 was fun to run at the strip would be a gross understatement.
Of course, this is the second year of production for the stylish little bike, and we say little because that's the way it looks. Actually, it tips the scales at just over 400 pounds, ready to ride. Essentially, the 400F is the first off-the-showroom-floor production bike in recent times to pick up on the Café racer styling motif, but the Café look is more than skin deep.
Honda has carefully tailored the 408 into a true mid-displacement sporting motorcycle. The end result is a bike that delivers reasonable economy, comfort and exceptional performance in terms of speed and handling. There are flaws here and there, but the way the motorcycle handles most situations manages to re duce the quirks to minor annoyances.
Honda has dispensed with most of the foo-faw and kept the CB400's styling clean and crisp. There are a few distractions, such as unusually large turn signal lenses and brackets, awkward looking front fender braces and a taillight big enough to serve duty on the roof of a police car. But the 3.7 gal. fuel tank is nicely squared off and is the only spot on the motorcycle where the main color of the bike is applied. Last year's dark blue hue has been replaced with parakeet yellow, but the attractive red model remains on the list, as well. All other painted surfaces, such as plastic snap-on side covers, frame, and headlight nacelle, are finished in black.
Chrome plating finds a home on front and rear fenders, exhaust system and assorted do-dads. Engine cases are finished in a classy silver, and overall quality approaches the upper end of the spectrum.
The short, narrow and low bars, high footpeg location and four-into-one exhaust collector tie into the bike's character perfectly. A shortish 54-in. wheelbase keeps the 400 in the compact category, the appropriate place for a sporting machine. This, however, puts the 400 pretty much out of bounds for behemoths, and relegates passenger carrying capabilities to the "occasional duty" column. Riders who look down at the 6-ft. level and spin a bathroom scale past the 190-lb. mark will begin to dwarf the bike; their comfort level will register accordingly.
Honda street bike seats have been hard and uncomfortable for some time; the CB400F's offers no respite. The wretched seat strap nestles dead center under most riders' rear ends and is all but useless to passengers, unless they want to get on more friendly terms with whoever's at the controls. The seat is not the only fly in the comfort ointment.
The low handlebars have an awkward shape, bending the rider's wrists at uncomfortable and unnatural angles. Couple this to Honda's hard, biting grips and you've got an area ripe for change. We had an opportunity to ride a 400F belonging to a friend who had changed both grips and bars. The difference was remarkable. Footpegs are rubber covered and foldable; the right one moves completely out of the way to allow the kickstart lever to be swung through its arc. A slightly stronger ball-detent would help prevent the footpeg from being kicked up out of position accidentally, which happened with us on more than one occasion. It comes as a surprise to set your foot down and find no footpeg!
Handlebar switches need a serious rethink by Honda engineers. Good ideas stop with the turn-indicator switch, which features a lane-change detent and good positioning in relation to the rider's thumb. The same can be said for the horn button, though the horn puts out little in the way of sound. Over toward the right, yet still located on the left handlebar stalk, is the high/low beam indicator. Getting to it with anything less than a 6-in. thumb is a chore. On the right there's the usual kill-switch and electric starter button.
Unfortunately, Honda no longer installs headlight on/off switches on its street-legal bikes, so one must contend with a glaring headlight, instrument lights, taillight and even running lights day or night, even if the bike is idling in a garage during a tuneup! Needless to say, battery problems crop up more often due to the constant load, particularly if the machine is run only on short trips.
A further look around the motorcycle reveals subtle but nice touches. The ignition switch also doubles as a fork lock when the double-sided key is depressed and twisted counterclockwise with the handlebars turned to either steering stop. A warning light panel includes neutral, high beam, oil pressure and turn indicators. Both tachometer and speedometer glow a soft green at night and the odometer features a trip reset. Two helmet holder tabs are accessible when the locking seat is flipped up. Located underneath is a plastic tool compartment that can be removed, allowing access to the air filter element. Previously, there was a red warning line on the face of the speedometer at the 70-mph mark. That's been deleted, perhaps because of the imposed 55-mph federal limit, or because the bike will no longer self-destruct above 70 mph.
Owners running the first year model 408 discovered they could run out of gas in the reserve position when there was still fuel left in the tank. And that's frustrating. But Honda has moved the petcock a few millimeters lower in the tank so that it can now run completely dry and add a few more miles to the reserve capacity. Our bike averaged 45 mpg for the test, and the reserve position was usually called upon at around the 140-mile mark. That gave us about 30 miles to hunt for a station.
Foot controls will fall into place for most sizes of feet, though riders with creaky knees will have to bend their joints more than usual because of the high peg location. The brake pedal features a loop guard that prevents the rider from hanging his foot up between the clutch cover and the lever. This year Honda diddled with it some because riders were getting their pant legs caught in the guards! It shouldn't happen now that they've moved the pedal out 4mm and increased the size of the wire loop.
On the shifter side Honda uses Heim-joint connectors to hook up the remote shift linkage, eliminating slop normally associated with a clevis-and-pin arrangement. This is another first-class touch.
Starting requires a practiced routine. With the petcock and ignition turned on, the choke lever must be placed in the full-on position. The starter motor begins cranking the engine over and things begin sputtering. The choke must then be nursed open and closed until the engine comes to life. But the 408 won't idle until it warms up some. And that takes a few moments, because the Four seems cold-blooded by nature. It eventually settles into a smooth idle and is perfectly happy about heading out into traffic.
Silence is the little Honda's forte. But there is enough personality left in the exhaust note and intake growl to let the rider know there's some spunk beneath him. So uncanny is the sound of the exhaust, that it almost seems as though the gases aren't emanating from the muffler's tip.
Revolutions build in an instant when the throttle is opened and unwind almost as quickly. With such effective muffling, one can hear the mechanical murmurings beneath the various engine covers, and it's these noises from within that tell lovers of high spirited motorcycles that this is the genuine article. The "whoop" sound produced when the 408 is doing its siren song at 10,000 rpm is enough to convince anybody that Honda's smallest "F" is more than an ordinary two-wheeler.
Clutch pull is light, but actuation is deceptive, since the hand lever has to be near the end of its release arc before driveline components start coupling up. Once underway, another annoying trait of Honda drive systems surfaces: excessive gear lash contributes a fair share of slack when the throttle is rolled off and on. At low traffic speeds in a line of cars, this problem rears its head and makes the rider wish for the open road once again. But even at highway speeds the driveline slop is noticeable, because throttle inputs transmit to driveline jerkiness unless a trained and careful hand is used on the twistgrip.
There is no room on a sport bike for mushy and ineffective suspension components. The Honda's aren't really mushy, they just lean more toward the harsh end of things. The Showa forks have 4.25 in. of usable travel, which is close to enough, but use a 40-lb. spring that is far too stiff. With 10 lb. of compression damping and 25 lb. of rebound damping, the end result is a fork that ignores many road irregularities to the point that control can be affected at high speeds on bumpy surfaces. We improved the fork action considerably by changing to a 25-1b. spring with a preload spacer, and worked out the fine points on the dyno for an easy fork-fix how-to that will appear next month.
This year's 400Fs have new rear shocks with increased rebound damping. But the oil capacity remains very limited, and riders who make a habit of going quickly through the twisty-turnies should consider replacement with S&W, Red Wing, or Koni shocks. All work well in that particular application. Spring selection will vary according to rider weight and loading conditions.
Aside from the unnecessary harshness, the suspension will not make too many owners unhappy. In fact, considering the standard suspension many street models come with these days, the 408 Honda doesn't fare badly at all. One can pitch the bike into corners with the footpegs on the asphalt and not get into too much trouble as long as the road is nearer to smooth than rough. There is no annoying tendency to nosedive upon braking, and the Honda hauls itself down from speed quite smartly.
Current motorcycle fashion dictates a rear disc brake, but the "F" gets along fine without it, though the drum does, upon occasion, get spongy when hot. The front disc squeaked every once in a while, but didn't make a habit of it. Feel and lever pressure were right in the ballpark. The only change we made with the brakes was to remove the front "fender" on the disc. It's really superfluous and only serves to prolong wetness on the disc in rainy weather by preventing water from slinging off. And really, who is foolish enough to believe that a mini-fender on a disc brake is going to keep a rider dry when it's wet out? Shades of Detroit from Japan.
The 408 is happy following the straight white line, but will prove itself agile and nimble in tighter situations. Engine vibration remains minimal except in the immediate vicinity of 5000 rpm and up in red-line territory. Cornering clearance will only be exceeded by the best of road jockeys. It's a good idea to roll off when it's used up anyway, since the standard tires will be at the end of their rope in tractive ability. This year the tires feature wear-limit indicators in the tread pattern, but we doubt that some will heed the warning until the carcass starts peeking through.
In its corner of the marketplace the Honda fares nicely. People will be quick to draw comparisons between it and Yamaha's new RD400, and a few will even throw in Kawasaki's KH400 Triple. The three machines are very close in ability and they all project a "performance" image. But the Honda 408 does its thing with eight valves, four carburetors, four cylinders and a single overhead camshaft; the strokes add up to four, as well. For many, those kinds of numbers are convincing enough. But if a little prodding becomes necessary, one ride down the road with the 408 reaching for redline in any of the six gears should do the trick.
Source:Cycle World 1974
By Frank Melling, Contributing Editor at motorcycle-usa.com.
"Thanks to reliability and spunky nature,the Honda CB400F certainly qualifies as a successful Memorable Motorcycle. I have been riding motorcycles for a long time and, fortunately, I have not lost any of my passion for bikes. I have ridden an awful lot of good bikes, a few mediocre ones and the occasional two-wheeled horror story but a few, rather special, motorcycles are truly memorable. One of these is the Honda CB400F1 which simply makes me smile with the memories of one of the nicest motorcycles ever to grace a highway.
The CB400 isn’t perfect but it is such a thoroughly good motorcycle that even its worst enemy would find it hard to say a word against it.
The CB400’s dad was the technically brilliant, but rather dull, CB350. A story about this bike - allegedly built at the behest of Sochiro Honda, who felt that a 350cc motor was the perfect size for a four-cylinder road bike - appeared recently in “Memorable Motorcycles”.
The problem was that whilst “Big Daddy” Honda loved the 350 - paying customers didn’t. This is not surprising since the 350 “4” was slower, heavier, more expensive and cost more to build than its twin-cylinder brother, the 325cc CB350 Dream.
In essence, the 350 “Four” was just too well-behaved a motorcycle. It brushed its teeth every morning, combed its immaculate hair, always wore clean jeans, which were freshly ironed, and only drank one can of beer on a Saturday evening. As your accountant it would have been fine. As a friend to party with, it was a disaster.
Honda’s answer was elegantly simple. The 350 “Four” was a fine motorcycle. It just needed some help to come out from behind the door and reveal its true potential.
Using its CB350 as a base, Honda bored out the four-cylinder powerplant to up to 408cc. The first job was to take the 350’s powerplant to the gym. Incredibly for such a sophisticated motor, the 350 was undersquare at 47mm x 50mm. Honda bored the new motor to take a 51mm piston which gave a marginally over square engine with a capacity of 408cc. They fitted new, bigger valves than the 350 plus a stronger clutch and a four-into-one siamesed exhaust system, which both increased torque and looked cool.
A sweet, close-ratio, six-speed gearbox meant that the motor could be kept on the boil and the delightful howl from the long, tapering silencer took us Grands Prix wannabees right back to the golden days of Honda racing with Jim Redman and Mike Hailwood.
The end result of Honda’s re-engineering was a bomb proof engine which gave a very healthy 37 hp @ 10,000 rpm - equivalent to around 100mph with a small, light rider tucked in tight on the fuel tank. This needs putting into perspective. 37 hp was slightly more power than a good 350cc Aermacchi or AJS 7R produced - and these were still competitive in Grands Prix four years earlier.
The chassis remained more or less unchanged in terms of being small and light but cosmetically the new bike was very much a sportbike. The flat ‘bars, narrow tank and seat and, most of all, an engine which positively demanded to be revved, all pointed to hard riding.
Honda encouraged the Cafe Racer image that the CB400 inculcated and this was both good and bad in terms of sales. The firm suspension and high-revving engine did not endear the bike to American riders, and the USA, even more so than now, was the critical market for Honda.
By contrast, European riders, with road-racing genes running through their bodies, loved the CB400. With the beautiful little power unit howling between 6,000 rpm and the redline at 10,000 plus, the Honda was a true racebike for the street. Hammered through rough corners, the firm suspension was in its element and best of all, it flattered the rider - regardless of his ability.
It may not have been the fastest bike in its day, but the Honda CB400F did perform well and won over many a rider. Only the brakes were less than ideal, but with four-stroke engine braking available, this was not a problem in the real world.
The 400 “4” was never going to beat the killer quick Kawasakis of the day, but it was an infinitely more refined and sophisticated motorcycle and one which won the hearts of all who rode it.
Today, CB400s are still recognised as outstanding motorcycles and this is a problem for would be owners. On one side of the coin the 400 is a mass produced motorcycle with no racing pedigree or exotic bloodline. It is, however, one of the nicest motorcycles ever built. The end result is that it will take a solid $5000 to own one of the best examples of these lovely little bikes - although considerably less will buy you a running, but un-restored example.
I got to know the CB 400 on a rather more personal level than I would have preferred. My College degree was as a teacher and I majored in English Literature. In English schools of the day, kids with a leaning towards Fine Arts never went near an engineering shop.
However, I had raced bikes from the first time I could afford an entry fee and had become reasonably proficient at gas welding simply because in those far off days bikes broke all the time and needed mending.
Colin Wilkinson, a long time friend of mine, was a good national class racer. He had campaigned a very fast Norton for many years but even by his tolerant standards was weary of it breaking. In August 1975 Colin purchased a brand-new CB400 road bike with the intention of riding it in the 500cc class of the Manx Grand Prix held over the incredibly tough Isle of Man TT course.
How reliable was the Honda CB400? Our writer's friend used it as a commuter and a Isle of Man GP racer! He arrived at my house with the bike having covered about 5 miles from new and asked that I cut and re-profile the exhaust pipes so that they tucked tight against the frame and fabricate a meagphone exhaust. The little Honda sat there with its chrome exhausts gleaming and I began to feel like the vet approaching the happy looking stallion which was about to have its life changed.
Fortunately, I got the cuts right and doubly fortunately none of the welds broke during the killer tough two weeks of the “Manx”. I would never claim to be a master craftsman but when it came to welding my work was always durable.
Colin made a few basic modifications to the Honda and raised the gearing slightly. These mods, plus Colin’s riding ability, were enough to give an 88-mph lap in the “Manx” and that was with the frame, suspension and motor completely standard.
Colin used it again in the “Manx” and then sponsored another rider who finished 8th in the Production TT. In between, the CB400 was used as a commuter bike and for recreational riding.
10,000 miles later, the Honda was sold - still running perfectly and, except for checking the valve clearances, with the motor completely untouched.
That’s why riders loved the CB400!"
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