Sunday, March 1, 2015

Honda Four

The ubiquitous Honda Four. Honda first released their original four cylinder motorcycle, the CB750, in 1969. (Technically the design is termed an “inline, transverse mounted, four cylinder” engine.) This bike, with just a few changes, mainly going from single overhead cam to double overhead cam in 1979, was sold right into the 21st century. In 2007 Honda was still selling the CB750 (at least in Japan) and a larger version of the four cylinder bike is still being made in 2015.

The successful design spawned many imitations from other Japanese brands as well as sister bikes from Honda. The term “superbike” was pretty much coined to describe the CB750, and this bike cemented Honda as the greatest motorcycle company in the world. Although a few riders would identify some other brand, Honda pretty much owns the title for producing the most sophisticated and technically advanced bikes around. Certainly they are the biggest seller of motorcycles and motorbikes in the world, a title they’ve held for several decades.

One of my favorite bikes of all time was my Honda 550 Four. It fit me so well and was a great around town bike. I also rode it from Denver to Lewistown, Montana, but it was a bit small for that trip. The smoothness and sound of that engine were unsurpassed at that time, and the reliability was legendary.

Four cylinder motorcycles are not new. Belgian arms manufacturer FN Herstal, which had been making motorcycles since 1901, began producing motorcycles with inline-fours in 1905. The FN Four had its engine mounted upright with the crankshaft longitudinal. That is, the pistons were in line with the front and rear tires. Other manufacturers that used this layout included Pierce, Henderson, Ace, Cleveland, and Indian in the United States, Nimbus in Denmark, Windhoff in Germany, and Wilkinson in the United Kingdom.

In those days internal combustion engines were not high efficiency performers, so it took a large displacement to produce adequate horsepower. Yet these all put the cylinders longitudinal to keep the overall design of the bike narrow. This meant the rear cylinders didn’t get as much airflow as the front causing problems with cooling. There were also torque effects with this design.

The 1923 design by Carlo Gianini and Piero Remor was the engine that fist demonstrated the transverse mount. After a slow start — it took until 1926 to get the motor up and running — it became the basis of the OPRA 500 GP bike in 1928 and eventually turned into the Gilera Rondine in 1935. The layout was a winner, and that engine was the basis of Gilera’s racers right into the 1970s!

The modern inline four-cylinder engine, mounted across the frame, has become virtually the default layout for today’s large bikes. Sure, there are plenty of alternatives, but the transverse four is one of the designs that’s closest to perfection, whether it’s in a Yamaha M1, a Kawasaki Z1, or an old Honda CB750.

The original Honda four produced 68 HP at 8,500 rpm which propelled its 481 pounds to a top speed of 125 mph. (These figures vary slightly from year to model year and with the test organization. I never had one, so I can’t contradict these values.) When Honda first brought this bike to market they weren’t sure how successful it would be, so they didn’t invest in high quality tooling. Now those original CB750s with what is often miss-named as “sand cast” engines demand the highest amount on the restoration market, some in the $30,000 price range for a bike that cost around $1,500 when first released.

This first model had a dry sump, which means the oil is stored in an external tank. This allows the engine to be a little lower in the frame because the bottom oil pan doesn’t have to store a lot of oil. Dry sump designs also provide some additional cooling in the circulation of the oil to an external tank, and it is easy for the manufacturer or an after market supplier to add an oil cooler. Later variations of the original Honda four had the simpler wet sump design.

Under development for a year, the CB750 had a transverse, straight-four engine with a single overhead camshaft (SOHC) and a front disc brake, neither of which was previously available on a mainstream, affordable, production motorcycle. Adding to the bike's value were its electric starter, kill switch, dual mirrors, flashing turn signals, easily maintained valves, and overall smoothness and low vibration both underway and at a standstill. Ten years later Honda added dual overhead cams to the CB750, and later models, from 1991, included maintenance-free hydraulic valves. Many of these features were unique in 1969, and now are the norm for most performance machines.

The angled-forward 736 cc engine design used many lessons learned during Honda's days of racing multi-cylinder machines in the Sixties, although the roadster relied on a single overhead camshaft and two valves per cylinder, in contrast to the racers with their twin cams and four valves per cylinder. The original engine was slightly under square with a 61 mm bore and a 63 mm stroke with 9.0:1 compression. Equipped with 4 - 28 mm Keihin carbs, the overhead cam was driven by a chain with a manual adjuster. The primary drive is gear and the secondary drive is chain. Disc brake in the front 19” wheel and drum in the back 18” drive wheel.

In 1975 Honda added a newer trim version of the basic bike called the Super Sport or CB750F. Those models had Honda’s own Comstar wheels and were sold from ’75 to 79. My favorite from that era had a black engine and canary yellow paint. It was a very pretty bike with a four-into-one pipe and a nice tailpiece behind the seat.

In 1979 Honda released the new CB750F with a dual overhead cam. I am not a fan of the trim on this bike as the tank flows into the side covers which extend onto the back. One might consider that a very modern and clean design, but I guess I'm just old fashioned preferring the previous styling. The seat was also redesigned, but — again — I’m not a fan of the overall style. This model continued on to 1986. A slightly different model called the CB750F2 was released in 1992 and produced for five years.

The latest model of 750 Four was the Nighthawk which was produced from 1991 to 2003. Although the 700cc Nighthawk (sized to avoid the 45% tariff for larger bikes) had the same basic DOHC engine of the earlier CB750s, this bike had a 6-speed transmission, hydraulic valve lifters, shaft drive, front bikini mini-fairing, gear indicator, and 16" front wheel. In 1984, the bike retailed at a MSRP of $3,398.

In 2007 Honda Japan announced the sale of a new CB750 very similar to the models sold in the 1970s. Announced as the CB750 Special Edition that was in the silver colors of the CB50 AMA racer of the 1970s and the CB750. It was offered in three color schemes reminiscent of CB750s previously sold. These bikes were intended only for release in Japan. Will we ever see a brand new version of this popular bike? That is the question.

In ’81 Honda introduced the CB900F. Style was reminiscent of the 750 but the new 901cc engine added humph. With 95 HP at 9,000 rpm and the four Keihin 32mm constant velocity carburetors, this was a bike to be reckoned with. But things were changing in the early eighties, so this bike was only produced for two years.

You see, early in the 80s a certain motorcycle company in Milwaukee started to complain to their congressmen that they couldn’t compete with the influx of Japanese large iron and got congress to pass a tariff on bikes larger than 700cc. Honda responded with the CB700SC Nighthawks. These toned down bikes had 696 cc displacement and a top speed of 147 mph. Again Honda went a little Disneyland in their styling adding a squared off headlight and miniature fairing to the front many compared to a bra. They also replaced the chain drive with a shaft and upped the ante to a six-speed transmission.

1983 would prove to be the final tariff-free year for foreign motorcycle manufactures before implementation of the five-year tax on foreign motorcycles over 700cc. Honda released the CB1000C that year. This was a continuation of the CB900C in many ways, but carried additional displacement to its engine. Both “custom” and “cruiser” models were available. The 902 cc engine was increased to 973, but otherwise the bike was unchanged. Still a 5-speed transmission but with dual ranges. The rider could select between two sets of 5 gears to match requirements. The shaft drive and a lengthy 64 inch wheelbase delivered a stable ride, while the 608 pounds limited performance somewhat, although 121 mph was listed as top speed.

The follow-on Honda CB1100 is a 1,062 cc (64.8 cu in) air-cooled inline four-cylinder naked bike that was introduced by Honda in 2010 as a modern successor to the CB750. At introduction the motorbike was available in Japan, Australia and New Zealand; it was later introduced to Europe and the US in 2013.

The CB1100 is styled as a universal Japanese motorcycle. The model underwent a revision in 2014, gaining a sixth gear and new gauge cluster. Honda also released the CB1100 Deluxe, an upgraded variant on the standard CB1100.

That's a 2014 CB1100 in the picture at the start of this article. The 2015 looks the same. Here's what Honda says in their brochure:

Though the CB1100 pays homage to Honda's long line of capable, reliable and fun street bikes, we wouldn't look to the past without looking forward. This is a modern bike for riders that love to ride. Its 1140cc, fuel-injected inline four is powerful and smooth, its chassis and suspension are agile and responsive, and it's comfortable around town or on weekend rides. For 2014, we're offering a Deluxe model with even more features. It’s a bike a whole new generation of riders is going to appreciate.

In addition to the new six-speed transmission on all CB1100s, this year, there's a Deluxe model that adds twin exhaust pipes, a slightly larger fuel tank, and a stitched-look seat. The Deluxe model also comes with ABS [automated braking system].

Honda’s inline-fours are timeless — some of the best engines in all of motorcycling. The CB1100 carries that tradition and takes it to the next level, displacing 1140cc and featuring air cooling to look the way many think a bike should — why hide under a fairing?

This is the largest Honda went with this basic inline four design. They did produce a six-cylinder, inline engine powered bike from 1979-82 called the CBX, but that was more a demonstration of technology than a serious bike since Honda was making and selling plenty of water cooled large bikes in its Gold Wing line first introduced with an opposing four engine in 1974 which continued to increase in size until it was replaced by the six-cylinder version in 1987. Today Honda still makes cruiser and touring versions of the Gold Wing with a maximum displacement of 1832 cc. That’s one big bike, but not part of the inline four family.

Honda’s history seems to be a quest to produce a motorcycle for every particular want or need out there. How else do you explain the single cylinder “Tourist Trophy 500” and the various unusual designs of V-twins from horizontal like a Moto Guzzi to V-fours and water cooled designs of many shapes and sizes. Meanwhile, the inline, air-cooled four design was expanded on and new versions and sizes were released every few years.

After introducing the four-cylinder CB750 motorcycle in 1969, Honda followed with a string of lighter fours featuring engines as small as 350 cc (CB350 Four, CB500 Four), and the CB400F 408 cc Four, produced in 2 models.

The popular air-cooled four spawned smaller siblings starting with the CB500 released in 1972. It is similarly styled to the CB750, but smaller and lighter, with an output of 48 bhp and a manufacturer's specified top speed of 102 mph. This original design was produced for two years

Like the earlier CB750 it sported a single front hydraulic disc brake, rear drum brake, electric starter, and SOHC eight-valve engine. The four-into-four exhaust pipes echoed those of the CB750. It was deemed a better handling bike than the larger model, although it was still no featherweight at 443 lb dry.

Unlike the earlier dry sump CB750, the smaller bike has a wet sump engine. Also, the primary drives were different, the CB750 having a duplex chain, while the CB500 had a "Hy-Vo" Morse chain.

Several CB500 machines were entered in the Production TT races on the Isle of Man in the early 1970s. Bill Smith won the 1973 500 cc TT Production race (four laps) riding one, 8.2 seconds ahead of second place Stan Woods mounted on a Suzuki T500 two-stroke twin.

The CB500 was a 498 cc (30.4 cu in) displacement machine. In 1974 the Honda CB550 with a 544 cc (33.2 cu in) four-cylinder was produced until 1978 when it was replaced by the CB650 increasing displacement to 626 cc by boring out the 550 block. Honda added domed pistons and produced 63 hp @ 9,000 rpm. The CB650's performance was comparable to contemporary DOHC 750 cc motorcycles because of it being built on the lighter, more compact chassis of the CB550. It was Honda's last SOHC aircooled straight-four engine, which was a culmination of the engine technology of Honda up to that time.

Like the earlier CB500 the original CB550K had 4 exhaust pipes and 4 silencers. The CB550K went through some minor iterations, the last being the CB550K4. Shortly after the CB550K was introduced, a second version of the CB550 was offered, the CB550F "Super Sport”.

The Honda CB650 is a four-cylinder middleweight motorcycle manufactured from 1979 to 1985 by Honda. The machine was largely based on the Honda CB550 and had the same frame, speedometer, and tachometer as the Honda CB550 of the 70's.

In 1973, Honda downsized the venerable four yet again with a very sporty model called the CB350. This smallest version of the inline, air-cooled, transverse engine was a 347 cc motorcycle based on the larger versions of the day. The motorcycle was manufactured in Japan from 1972 to 1974. In 2012, Motorcycle Classics magazine said the 350F was "the smallest displacement multi-cylinder motorcycle ever to enter into full-scale production." There were no changes to the 1973 model, but Honda designated the 1974 bike the CB350F1.

Soon after production was discontinued, it was replaced by the CB400F. Although Honda had a 350 Twin that critics said was more powerful, lighter, and cheaper, many felt the 350 Four was faster and smoother running.

The apparent fact that Honda was “fine tuning” their product line is indicated by the fact that the CB350F wast the successor to the CB500F and was predecessor to the CB400F. The Honda CB400F was made by Honda from 1975 through 1977.

For the most part, the CB400F was simply an upgraded version of the 350 model from the previous year. The most striking change was the swoopy four-into-one exhaust system that snaked around the frame, converging into a single muffler on the right side of the bike. Check the end of this article for a picture of that fine exhaust system. Also noticeable were the angular fuel tank and flat cafe-style handlebars, all of which gave the bike a more racer-like look and feel than the rather pedestrian 350.

Although aimed at the sporting segment of the market, the four-stroke CB400F did not have the acceleration of the competition's two-strokes, particularly the triples from Kawasaki. But what the CB400F engine lacked in power it made up for in refinement, the small-displacement four-stroke being smoother, quieter and much more economical than the two-strokes. To help keep the engine in its power band, Honda employed a six-speed transmission — something of a rarity at the time.

The CB400F was a very successful motorcycle in club or privateer racing. Kaz Yoshima and other racers were able to take Honda's little 408 cc engine up to 490 cc and with the addition of other racer options, this small bore was considered a “giant killer.”

That is the evolution of the versatile and popular transverse, inline four from Honda. Over the nearly 50 years of its production it went from a single overhead cam design to DOHC. Honda added hydraulic valves, fuel injection, electronic ignition, and even some fairing as the basic design was improved and expanded. Four valves per cylinder and automatic primary chain adjustment are just a few of the performance and reliability enhancements added since the original CB750.

The transmission went from 5-speed to 6 and there was even an automatic transmission available at one time. The original CB750 pioneered disc brakes and the latest versions even add Automatic Braking Systems. (The first disc brake was actually on the CB450K3 model, and that led the way for the CB750 released that same year.)

Still for sale today, a popular 1100 cc version has continued its role as the successor to the first “superbike.” Although I personally find the larger Honda fours both too wide and with a seat that is a bit too high, leaving me looking at V-twin designs, the smoothness and power of this engine, as well as its superb reputation for performance and reliability makes it a very popular bike for current riders as well as nostalgic collectors.

Hard to imagine how old this basic design is. It's approaching 50 years since it was first produced. Also hard to imagine the impact the Honda Four had on the riding public. Many beautiful design examples exist, but my personal favorite is the serpentine bent pipes on the CB400F. No modern sculpture in the Louvre or the Metropolitan Museum brings as much emotion to me as that sculptured metal and the promise it holds for a fast and joyous ride. With a roar like a European sports car, a Honda Four will still turn heads even in this high-tech, computer saturated 21st century. I'll take one in the canary yellow please.


Disp. 325 cc
19.9 ci
408 cc
27.1 ci
498 cc
30.4 ci
736 cc
44.9 ci
901 cc
55.0 ci
1062 cc
64.8 ci
@ rpm
Weight 328 412 443 481 514 536
MPG 55 50 45 35 32 30
0 - 60 sec 6.5 6.3 6.0 5.2 4.5 4.0
1/4 Mile Sec
Trans. 5-spd 6-spd 5-spd 5-spd 5-spd 5-spd
Top Speed 98 106 110 125 130 138
Price New $1100 $1200 $1270 $1495 $3495 $3698

CB500 updated to CB550 in 1974

1 comment:

  1. Enjoyed the article , one error I found was the displacement of the 1983 CB1100F . It's 1062 CCs (64.8ci )