From our Old Bike Archives – Issue 67 – first published in 2017.
Story: Tony Sculpher • Photos: Tony Sculpher and Jim Scaysbrook
Inspired by German design, built in Japan. Honda’s first 250cc OHC model was the start of big things to come.
It is well documented and universally perceived that Soichiro Honda was an exponent of the four-stroke engine, but his early motorcycles were in fact two strokes. From one of my Honda publications it is claimed that the idea for the company’s shift to four stroke engines actually came from Soichiro Honda’s business partner Takeo Fujisawa and their engineer, Kiyoshi Kawashima.
Traditionally, the Honda Motor Company had only manufactured smaller capacity motorcycles for the commuter market, which were in high demand in post-war Japan. The 1955 – 1956 SA250 + SB350 Dream models (and the subsequent 1957 ME250 + MF350 Dream) were the first 250 cc and 350 cc models that Honda Motor Company manufactured, and were the first step by Honda to enter the sports motorcycle market. These new models featured a number of technologies and features that the Honda motorcycle brand would later become famous for.
From my research it became quite clear that this new range of Honda models was a direct result of events that Soichiro Honda experienced during the early 1950’s; the first being his two-month trip to Europe commencing late May 1954 to visit established manufacturers; and secondly the relaxation of duty and tariffs for imported motorcycles to Japan for domestic manufacturers (only), encouraging those very same manufacturers to buy in an overseas motorcycle for any form of “technical inspection” (read: copying).
Soichiro Honda and Takeo Fujisawa wasted no time when in Europe. They toured major motorcycle manufacturers such as NSU and Kreidler in West Germany, Moto Guzzi in Italy, and Triumph in England, and took every opportunity to examine major European brands in their “fact finding” tour. As a designer and manufacturer, Soichiro Honda recognized the outstanding German design and high quality finish of the NSU and Horex motorcycles: they were the benchmark for his philosophies. They also visited automobile manufacturers DAF in Holland and Volkswagen in West Germany to investigate their production techniques. Even the German and Italian-made scooters that were ever-present in European streets, and all that was displayed in retail motorcycle dealerships, were not ignored. Soichiro Honda formed an admiration for the power and speed of the NSU racing machinery that he witnessed at the Isle Of Man TT races. And it is this admiration of the NSU brand that would heavily influence his own new designs from the early 1950s onwards.
There is an infamous (and unsubstantiated) story of when Soichiro Honda was returning home from his 1954 European trip, he had three suitcases and was only allowed two on the plane. Wearing as many clothes as he could, he left his last suitcase containing the balance of his clothes at the Rome International Airport. His priority was to bring home the valuable cargo of motorcycle components including tachometers, spark plugs, rims, magnetos, carburettors, drive chains, and tyres that he had purchased on the trip. These were duly inspected and copied by the Honda Motor Company and their selected local component suppliers.
As stated, the design and manufacture of the Honda SA + SB and ME + MF series were the result of the above events. But these new single cylinder overhead camshaft Hondas were expensive, and were marketed as top of the range, prestige, luxury models for the Japanese domestic market. Their production runs were not large. The emergence of the new 344.6 cc SB model also signalled that Honda was now ready to expand their products outside the traditional commuter engine capacities of up to 250 cc. The SA + SB models with their German appearance (notably the engine castings, the pressed steel frame, single seat, carrier and rear mudguard design) mirror both the Horex Regina models and the NSU models from the early 1950s. The later ME + MF models with their leading link front end tended to look more like the early 1950s NSU Super Max. In fact, the SB350 Dream owner’s manual openly declares that the motorcycle has been manufactured “ to maximize that comparable to NSU of Germany .” The 89 cc J series Benly models released in 1953 were copied from the smaller NSU Fox design, but with some of Honda’s own improvements, especially the design of the telescopic front forks.
The German styling influence remained in the Honda motorcycle range right into the 1960s, especially those models that featured pressed steel frames, for example the C72 and C77 Dream models. If you see one of these 1960s Dreams with the single saddle option, you can clearly see the 1950s German design. I strongly suspect that Honda added the leading link front forks to the ME + MF Dream models to emulate current trends seen in Japanese racing motorcycles from around 1957 onwards. Remember that the most prestigious event on the Japanese racing calendar was the Mount Asama races and these races were on unsealed roads of volcanic ash. Many of the racing motorcycles at Mount Asama featured leading link front ends in order to adapt to the unsealed roads.
The single cylinder SA250 engine is Honda’s first ever overhead camshaft engine, and their first model with a four speed transmission. With this engine, Soichiro Honda was already stamping his mark as an individual manufacturer by innovating – he added his own design of chain drive for the camshaft – eliminating the gear drive of the Horex Regina engine he copied. The engine crankcases and exterior covers of the Honda engine all look similar to those of the Horex. By no means was Honda the first manufacturer of overhead camshaft motorcycle engines in Japan: Sanyo, Showa, Pearl, Hosk and Portly all had attempted overhead camshaft designs of their own, unfortunately without good design which affected reliability. Liner had also duplicated the English Sunbeam in-line twin design, again with an overhead camshaft layout.
The carburettors used on the SA + SB and ME + MF series are a metric version (copy) of the English Amal, and were manufactured by Mikuni in Japan. What is not recorded is what had transpired to gain the manufacturing rights. My suspicions are that back in the mid 1950s, this type of copying was mostly ignored by the established manufacturers in Europe and North America. As Japan was only manufacturing motorcycles for their domestic market and (to the outsiders’ knowledge) not exporting to their markets, Soichiro Honda was not considered a threat to them when he visited their factories in the (Northern hemisphere) summer of 1954. His timing was incredibly lucky as the manufacturers happily answered his many questions without hesitation. Little did they know that they were fuelling the fire…
The front forks on the SA + SB series imitate English Norton forks of the era, right down to the imperial dimensions for the fork seals. The headlamp cowling, including the two horizontally-split housings complete with chrome side mouldings, are reminiscent of the 1950 Triumph Thunderbird. The rear swinging arm design was definitely leading edge technology for Japanese manufacturers in the mid 1950s. Most brands offered traditional plunger rear ends, with exception in the case of the early 1950s Honda Benly models’ combined rear torsion suspension and the engine design, which were copied directly from the NSU Fox with improvements.
Interestingly, Honda innovated with fibreglass technology early. The SA + SB and ME + MF series feature early fibreglass panels including the upper headlamp shroud and their left hand side covers. This also may be an attempt by Honda to help reduce the overall weight. The portly single cylinder 1955 SA250 Dream weighed in at 171 kg (377 lbs) – a little more than a four-cylinder 1972 Honda CB350F at 169 kg (373 lbs) dry. The performance was also disappointing due to the poor power to weight ratio. They were simply too heavy and underpowered to compete with the lighter twin cylinder two strokes offered by some of the competition, especially the Suzuki Colleda, with an incredible (for 1955) 16 hp on tap.
The SA + SB Dream models were released in May 1955 (Spring in Japan and the Northern Hemisphere), and again were clearly positioned to sell as the top of the line/premium luxury/touring models from Honda. The materials, engineering, machining tolerances and heat treatments of the Honda products were better than the competition. The machining was a direct result of Soichiro Honda’s investment in modern and very expensive West German, Swiss and American manufactured machine tools purchased during 1953. Due to the increased productivity created by these new machine tools, coupled with lower production costs, Honda motorcycles were increasingly competitive in cost and quality, especially as production volumes increased.
Honda subsequently outsold its largest rival – Tohatsu – in September of 1955, becoming the largest motorcycle manufacturer in Japan. Due to their superior reliability, in 1956 the Honda Motor Company commenced offering a twelve month warranty for their entire range, something their competitors simply could not offer, nor afford to support.
For 1956, the SA250 Dream was lightened to 164 kg, and featured a higher 12 hp@ 5,800 rpm, giving a top speed of 100 km/h (62 mph). The 1957 ME + MF Dream models with their increased power helped to mitigate the obesity of the earlier models, but better performance was coming when Honda moved to the twin cylinder C70 series offered from late 1957 onwards.
The SA250 featured a pressed steel frame, with tubular engine front support, using the engine as a stressed member. It had a pressed steel rear swinging arm with twin shock absorbers. Front forks are telescopic type, and leading link on the ME + MF series. Front and rear brakes are single leading shoe, with full width pressed steel hubs on 19” diameter wheel rims (18” on ME + MF series). The drive chain is fully enclosed on the right side. There is a single cantilever saddle, with rear carrier. Mudguards and right side covers are pressed steel, while the headlamp cowling and left side cover are of fibreglass construction. The fuel tank is Chromium plated and electrical system is 6 Volt.
This particular 1956 SA250 Dream spent most of its life residing in the Ibaraki prefecture, north of Tokyo. Privately imported in 2015, this is the only SA250 Dream in Australia and possibly the oldest Honda four stroke motorcycle in Australia. There is a later model 1957 ME250 Dream in Australia, but there are numerous differences from the SA250.
Selecting and purchasing a motorcycle by photographs and emails is a risky business. My SA250 Dream was almost complete, and this aided the restoration process. Remember that there are no new-old-stock parts that are readily available, and you only have what you see to restore. The best advice I can give any restorer contemplating restoring a 1950s Japanese machine (especially a non-export model), is to source a machine that is as complete as possible. As I progressed with the restoration, it occurred to me that there was very little (virtually nothing) in the way of technical information; no workshop manual, let alone finding any used spare parts, or any of those treasured new-old-stock parts. There is a language barrier between Japanese and English, and most of the information I found was only in Japanese. My Japanese language skills are very poor, so to translate documents such as the wiring diagram was indeed another challenge.
Due to the condition and the irreplaceable nature of the components, I commenced the restoration with the smaller electrical components including the handlebar switch and the stop lamp switch. This ensured I had the most time available should I need to improvise, or if lucky enough, to find a second hand replacement. The wiring had to be completely replaced, as it appears to have experienced some form of electrical short circuit in the back part of the wiring.
The engine was in surprisingly good condition, however the previous owner had completed some poorly conducted internal repairs which all required re-addressing. The valve rocker faces had been poorly ground, ultimately damaging the camshaft lobes. The piston rings had no gap and I was thankful that I did not try to run the engine before disassembly, or it may have seized. The cam chain tensioner bolts were all loose. I enlisted my friend Mike DeWith to complete the repairs and the correct assembly of the engine.
Although this particular SA250 Dream was originally the black colour, I elected to re-paint in a red colour as close as possible to the red that was originally offered. After much deliberation, I chose Venetian Red, and I am sure the end result is attractive without looking inaccurate for the age of the Honda. The panel repairs and paintwork were all completed by a good friend, and fellow VJMC member, based in Melbourne.
Not so surprising was the fact that no-one I knew had really heard of this Honda as it was a Japanese domestic market model only and not officially exported. They are a rare commodity. I have been researching and canvassing other 1955-1957 Dream owners and restorers for information on the whereabouts of these models. From my research for the compilation of an International Register, there seems to be semi-regular offerings of both SA250 and ME250 Dream motorcycles for sale from Japanese websites of exporters such as RMD Motors near Tokyo, but the total numbers surviving in Japan are not known, and are proving difficult to research. The register now lists eight 1955-1956 SA250 Dream models – five in Japan and three internationally including this one in Australia. To date we have not found any of the SB350 Dream models. We have recorded twenty of the later 1957 ME250 Dream models, and only four of the 1957 MF350 Dream models, either internationally or within Japan.
The cast iron on a 60 year old Honda was not of a very good quality. Back in the 1950s Japan had very poor material resources; supplies of high quality steel and materials were in high demand and were unreliable. Japan offset this shortage by importing any old or waste steel (including old cars) for recycling, and this recycling reflected in the quality of the cast iron and steels utilized in production.
On my SA250 Dream, there were several teeth missing on the sprocket, and all of them were worn to some degree. Replacing the sprocket only on the cast iron brake drum creates a large problem – any welding of the new sprocket to the existing aged cast iron would create warping of the brake drum, making the assembly unusable.
Do your research and find a gear cutting manufacturer who will measure and write a programme for his Computer Numeric Control (CNC) milling machine to fabricate a complete new assembly. My machinist fabricated the new sprocket assembly from fine grained 3D ductile cast iron, which is stronger than conventional cast iron. This may sound expensive, but you will only ever do this once for the life of your Honda.
Specifications: 1955 Honda SA250 Dream
Engine: Single cylinder, single overhead camshaft.
Maximum speed: 98 km/h
Wheelbase: 1364 mm
Weight: 171 kg