Saturday, December 27, 2014


In the latter part of the 80’s, Honda sleeved down the motor from the off-road XR600, chromed it, mated it to a dual-shock vintage-y chassis, added a bum-stop seat, low clip-on handlebars, and wire spoke wheels, and created the GB500 TT, a stone reliable, retro-modern 1960’s café racer.

(Introduction paragraph paraphrased from the Clubman TT website,

The café racer is a light-weight, lightly-powered motorcycle optimized for speed and handling rather than comfort. The bodywork and control layout of a café racer typically mimicked the style of a contemporary Grand Prix roadracer, featuring an elongated fuel tank (often with indentations to allow the rider's knees to grip the tank), low slung racing handlebars, and a single-person, elongated, humped seat.

A signature trait was the use of low, narrow handlebars that allowed the rider to "tuck in" — a posture with reduced wind resistance and better control. These handlebars, known as clip-ons (two separate bars that bolt directly to each fork tube), clubman or ace bars (one piece bars that attach to the standard mounting location but drop down and forward). The ergonomics resulting from low bars and the rearward seat often required rearsets, or rear-set footrests and foot controls, again typical of racing motorcycles of the era. Distinctive half or full race-style fairings were sometimes mounted to the forks or frame.

The bikes had a utilitarian, stripped-down appearance, engines tuned for maximum speed and lean, light road handling. The well-known example was "The Triton," a homemade combination of Norton Featherbed frame and Triumph Bonneville engine. It used a common and fast racing engine combined with a well-handling frame, the Featherbed frame by Norton Motorcycles. Those with less money could opt for a “Tribsa” — the Triumph engine in a BSA frame. Other combinations such as the "Norvin" (a Vincent V-Twin engine in a Featherbed frame) and racing frames by Rickman or Seeley were also adopted for road use.

(Since Norton would not sell a bare frame, many riders would purchase the complete motorcycle and then remove the Norton engine. The famous frame got its name from Harold Daniell, a successful Isle of Man TT racer with three victories and several placings in the Tourist Trophy races and the Manx Grand Prix. After testing the new Norton frame in 1950 he declared that it was like "riding on a featherbed" compared with riding the "garden gate" — and it has been called the featherbed frame ever since.)

The Honda GB500 TT was a motorcycle introduced in the 1980s. First marketed in Japan in 1985 in two 400cc and one 500 cc version, followed by a third 400 cc version for Japan and finally a 500cc version for the US.

(The "Tourist Trophy," or TT, derives its name from the Tourist Trophy motorcycle races on a 37-mile road circuit in the Isle of Man off the coast of England.)

The GB500 engine was based on the motor from the Honda XL600, a dry-sump, four-stroke dirt bike. The four-valve single cylinder engine featured a radial four-valve combustion chamber, along with a tubular frame, wire wheels, clip-on handlebars, solo seat, seat hump, and pin-striped gas tank. The styling resembled TT single-cylinder racing bikes (such as the Manx Norton, the BSA Gold Star and the AJS 7R) that were prominent in the TT until the 1960s.

In the USA, GB500s were imported for model years 1989 and 1990. In 1992, a third-party exported 1,000 unsold Honda GB 500 Clubmans from the USA to Germany as unofficial import vehicles.

The GB500 looked like an antique, but it was a modern machine. A single-cylinder, 499cc overhead cam engine was similar to a multitude of British machines that had been powered by "thumper" engines in their heyday and the GB embodied the emotion. A two-into-one exhaust handled the departing gases and the muffler was finished in chrome. (Although a single cylinder, with two exhaust valves, there were two exhaust pipes.) Starting the GB was accomplished via electric start or kick-start pedal.

Released in 1989, it had been many moons since Honda included a kick-starting on a street-going machine. The solo saddle was truncated by a small rear cowling that, along with the classic shaped fuel tank, were draped in Black Green Metallic paint and offset with gold pinstripes. Everything about the Tourist Trophy said "classic," right down to the spoke wheels at either end. Low mounted handlebars or "clip-ons,” and a five speed gearbox complete the list of features. This bike would feel right at home at the Isle of Man.

A drop in the price of $500 for 1990 probably spoke to the poor sales of this very un-Honda, Honda. Dropped from sales in the US in 1991, perhaps it was replaced in the eyes of Honda management by the new, sportier looking Nighthawk incarnation of the venerable CB750.

It is hard to understand why Honda built a bike like the GB500. Its engine configuration, styling, and even its name tie to an earlier time in motorcycle racing. A time when bikes such as the BSA Gold Star were the sporting bikes of choice and the Isle of Man TT was the premier motorcycle event in the world. But that still leaves the question of "why?" It is almost as if someone at Honda suddenly realized that they had never bulit a 500cc single-cylinder sport bike, and decided that it needed to build one to fill a perceived void.

Even the numeric code was a bit of a mystery. Honda had well used the letter C and also V, X, F, S, and even R and P. GL, of course, was used since the first Gold Wing in 1975. But GB is rather unique. Could it actually stand for "Great Britain?" Is the 500 TT just a tribute from one small Pacific island country to another small island nation in the Atlantic?

The main feature of the GB500 was a 500cc, single-cylinder, overhead-cam four-stroke. The head had four valves in what Honda called a Radial Four Valve Combustion chamber (RFVC). To dampen the vibration inherent in a big single, the engine was equipped with a gear-driven balancer shaft.

The RFVC head has the valves arranged radially and none of the valves are on the same plain giving a hemispheric shape to the combustion chamber. Think of all the valve faces resting on the surface of a ball and how they all point out and away from each other.

Other four valve engines have a pent roof design where the intakes are usually on the same plain and the exhausts are on the same plain. This gives the combustion chamber a shape like a tent.

How is one better than the other … well … pent roof chambers have the advantage of a squish area that makes them less prone to detonation. Hemi's on the other hand have a nice even burn. In theory the hemi-head has advantages and disadvantages. I note that the latest designs of both automobiles and motorcycle heads tend more toward pent roof and squish band designs. The entire semi vs. pent-roof argument all goes back to european designs. Neither the Japanese nor the Americans were first to these high performance head and valve designs, although Honda certainly has made a name for themselves as a four- (or three-) valve engine company. One always wonders about the level of cross-pollination between Honda motorcycle engineers and the automotive group.

For relief from the ritual usually required to start a big single, the GB500 was fitted with an electric start and an automatic compression release. Honda claimed an output of 40 horsepower for the engine. Every bit a throw-back and every bit a modern example of precise Honda engineering.

With a counterbalance that quells vibration, about 33 stock horsepower, and a 7500 or so redline, it is an engine that needs to feel its oats. Somewhere, right now, on some winding slab of asphalt, there’s a happy owner winding this thumper out. I’m sure you couldn’t wipe the smile off his face with a roll of paper towels. I just wish that rider was me.

The styling of the GB500 is very attractive, particularly if you were fond of British café racer styling. With wire spoke wheels, dual rear shocks, a separate speedometer and tachometer in chromed housings, the small front fenders, clubman (clip-on) bars, the seat tailpiece, and the black green paint with gold pin-striping, and you had a bike that fitted the vision of what many people thought motorcycle of the earlier era should look like. A very attractive motorcycle, indeed.

Although only sold for two years due to poor marketplace performance, the bike has a special group of followers including this definitely anglophile rider. I’m actively seeking one of these special bikes for my collection.

There is even special websites dedicated to this single Honda model. Check out and

At this website, the rider looks suspiciously like yours truly.

Owners of these special bikes are almost a cult. A much smaller group that those that still ride classic vintage Hondas such as a CB77 Superhawk of the original K0 or K1 versions of the CB450 known as the “Black Bomber.” The few lucky owners of this Honda “Clubman” would not part with their bike for love or money. I suspect they keep the machine safely parked in their living room, or — even better — their bedroom. But trust me, these are not museum pieces. No, any owner would spend his (or her) weekends out on the road, possibly humming some British folk song.

Check out these pictures of the original prototype, a 1962 AJS 7R, 350cc. Now you can see where those tricky Japanese got the look. It’s a simple recipe: one stone-reliable Japanese thumper in one British style frame, and you’re ready for a trip to the Isle of Man. I can recommend several good pubs in Douglas or Castletown. Just park your bike outside.


Norton Manx

Honda GB500 TT

1 comment:

  1. Well written and all can see the comparison with the AJS 7R.... I live in the I.O.M. yup! he is quite right about the pubs in Douglas and Castletown! come over! assured of a warm welcome! I have met here many American bikers at both the TT and the later Manx meets!