Tuesday, January 15, 2019

Eighth-liter wonders… the Honda 125... singles, twins, fours and fives!

Street bike models
As Honda’s new Benly J-series machines evolved, from 1953-58, the engine displacement began at 89cc and eventually rose to a full 125cc, with the introduction of the 1955 JB Benly model, which took advantage of a new law allowing for this larger-sized engine in Japan. There were severe restrictions on manufacturers in the 1950s, which eventually loosened up, as the decade passed.

The Benly J-series 125cc engines doubled in horsepower from 4.5 to 9.5 between the 1955 and 1958 editions, as these simple pushrod-powered bikes fought to compete and overcome challenges from the hundreds of other Japanese motorcycle manufacturers in post-war Japan. When the limit was reached for the single-cylinder models, the “new” 125cc Benly models became OHC, short-stroke, twins with 44x41 engine dimensions. Similar to the new 250-305cc Dream twins, the first-year 1958 models, named C90, came without electric starter motor options.  By 1959, Honda expanded the line-up, adding the new electric-start model C92, along with a highly-engineered “Sport” version called the CB92 Benly Super Sport. And with a twist of the boring bar, new 154cc models, based upon the 125cc engine design were announced as C95 and even a CB95 for that one year.

All Benly twins rode on leading-link suspension up front and a simple pressed-steel swing arm in the back, located by a pair of non-adjustable telescopic shock absorbers.  The standard Benly 125-150 models looked like little 7/8ths scale versions of the larger 250-305 Dreams, which came to market in late 1957, thus they have become known as “Baby Dreams” by some owners.

These sturdy little OHC twins featured a single carburetor which split the mixture into each cylinder alternately, due to the 360 degree crankshaft configuration. Ignition was a simple single set of contact points operated from the end of the crankshaft for accurate ignition timing. A single 6v dual-tower ignition coil was bolted up inside the backbone frame with its twin spark plug wire leads dangling downwards connecting to small 10mm spark plugs for the first few years. Eventually, the spark plug size was increased to 12mm and numerous changes to crankshafts and other engine internals yielded a fast and reliable small-bore street machine. The C92 models were rated at 11.5hp at 9,500rpms, while the CB92 Super Sports model carried a 15hp rating at 10,500 rpms; power unheard of in those days. Honda made specific tank badges for most of their models, until 1968. The little Benly models used “Benly” only badges for 1959-61, then switched to “Benly 125” badges for the remaining years of production, including the use on the CR93 street bikes.

American Honda did import a 1959 CA92 125cc model for just that one year, followed by the larger-bore 154cc CA95s (named the Honda 150Touring), which sold from 1960-65. The US did not impose cc restrictions on small bikes and riders, unlike Japan, so it was “the bigger the better” for the US market enthusiasts. Honda responded rapidly to the unfolding new bike market, offering the 305cc options for the larger models, over the almost identical 250cc versions.

Other than the CB92 Super Sport models, of which only about 1,000 came to the US, there were no other 125cc offerings in America until 1967, when the SS125A/CL125A models were introduced. Design-wise, the “new” 125cc twins were visual duplicates for the early Benly models, which shared the “side camchain” feature, but it became apparent that almost none of the early Benly parts were being shared with the new-generation machines.

There was a Honda CB125 (CB93) model, which was a 125cc version of the CB160 (CB96), but they were not officially imported into the US.  The mysterious Honda CBXX codes were finally dropped in 1968 for the most part, when the bikes were designated by their displacement size; i.e. CB350, CL175, CB450, etc.

In the US, only the pressed-steel framed models (with 17” wheels) were offered in that 1967-68 timeframe, whereas the domestic and European editions had twin-carb, 5-speed versions stuffed into tubular frames with full 18” wheel sets. Non-US models were marked as CB125K3 for the early models, which featured CB77-style 2:1 instrument gauges with tach and speedo in one single oval-shaped unit. These bikes featured an 11,500 rpm redline and all the full features of the larger CB/CL175 models, which were seen in the US.

Honda did use the single carburetor engine in the domestic CD125 models, again not seen in the US, but they were delivered in Canada at the same time as the SS/CL125A models were sold in America. In photos of European models, the same side-cam engine was used in various frame/chassis setups, with variations in the locations of the ignition systems and other details.

When Honda finally retired their aging 4-speed S90/CT90/SL90 horizontal singles in 1969, their replacement was first released in Japan as the CB90, a nearly-vertical OHC style single with a 5 speed transmission. By 1970, the engine was bored out to 100cc and released to the US markets in CB100 and CL100 versions. These continued until 1973 when Honda broke out the boring bar, once again, bring the displacement out to 122cc as the new CB125S0 edition. It was basically a bored out CB100 and continued to have the same drum-brake as the base 100cc models. When Honda rolled out the 1974 version of the CB125 (CB125S1), enthusiasts were surprised to see a full-featured model with a tachometer and a clever, mechanically-operated disc brake in the front wheel. Curb weight climbed only 10 lbs from the near-200lb weight of the S90/CL90 models of the 1960s, but the bikes top speeds barely improved at all. While many S90s seemed to be able to touch 70mph, the CB125S1 was a 65 mph machine, even with a tail-wind. Just about all of the 100-125cc editions had a single 22mm carburetor attached, with only minor jetting setting them apart.

(Side-bar story: Your author bought and tuned a 1974 CB125S1 for the 125cc production class racing in Southern California. At the end of the season he captured the 125cc class championship in both the CMC and AFM racing organizations. With help from Yoshimura-supplied engine parts, the bike regularly reached speeds of 80+mph and had the best brakes of the class.) 

The CB125S1 and 1975 CB125S2 models were identical apart from their paint schemes, still sharing the same one-piece cylinder head design inherited from the CB90/100 models. The minimalist cam bearing support of that cylinder head design lead to worn cam/head bearings, causing the camshafts to wobble around in the head during operation. With the point cam mounted at the end of the camshaft, ignition timing also suffered inaccuracies, especially at high rpms. Hard-core racers, who campaigned the SL125 variants in off-road racing, resorted to machining the camshaft and cylinder heads for needle bearing conversions to help secure the camshaft firmly in the cylinder head.

By 1976, the revised CB126 ’76 models gained 2ccs, a new 2-piece cylinder head, but lost their tachometers. The cylinder head was also redesigned with a split-port intake runner to help boost mid-range torque and engine efficiency and the carburetors were finally rubber-mounted to help reduce fuel frothing at high rpms. Continued use of small-bore carburetors and mild valve timing yielded reliable performance, but nothing truly noteworthy.

The 1977-78 editions were again just a color change upgrade. By 1979 the front disc brake disappeared, replaced by the generic drum brake package seen in the first editions. The 1979-80 models continued much the same as the earlier editions but with new mufflers and a styling package. Finally a CDI ignition package was installed for the 1981-84 models. The 1984 models were upgraded to 12v, after 14 years of suffering with tiny 6v electric power.
Honda did not offer any CB125S models in 1983, owing to a backlog of unsold models in their inventories. The 1984-85 editions were all made in Brazil, as Honda phased out the 125cc streetbike line-up for good.

Not sold in the US, but were offered to MSF course sites was the CB125T. This engine was a derivation of the US-spec CM185T and CM200T designs (forerunners of the Honda 250 Rebel). While the US “Cruiser” models had 360 degree crankshafts,  6v electrics, single carburetors and 4-speed gearboxes, the CB125Ts came out of the box with 180 degree crankshafts, 12 v electrics, dual carbs and a 5-speed transmission. The first-generation bikes came with regular, spoke wire wheels and the mechanical disc brake seen on the CB125S models.  The dry-weight figures were in the 250 lb range, but these bikes would pull upwards of 80mph at their 12k rpm redlines. While the early bikes never made it to the US, American Honda worked out some kind of a lend-lease program with the Motorcycle Safety Foundation organization and supplied some specially-equipped CB125TT models as “learner” bikes for the rider programs. The bikes were never supposed to be titled or registered in the US, due to lack of EPA approvals on that model.

The CB125T2 models had Comstar wheels, a front hydraulic brake and other amenities in keeping with the design themes of the 1980s and early 1990s. The bikes were widely distributed throughout Europe, Asia, Africa and Australia, where countries created rider/taxation restrictions on certain classes of riders.

Workhorse model CG125 Honda singles were mass-produced and featured a plain, pushrod engine configuration vs. the typical OHC models sold as a higher level model. Low-powered but reliable as a rock, these bikes suffered at the hands of non-mechanics worldwide, where they were treated more as a transportation appliance than as a spirited means of riding joys. Just another example of Honda targeting a specific market with their very “Benly” product line. Convenience over all other considerations, with reliability as a must. Millions would agree that the target was met successfully.

Roadracer 125s
Primarily offered as a high-performance street machine, Honda did offer CB92R models, kitted for 125cc class road racing in the US. Starting with the base CB92 machine, a long list of “YB” race kit options was available as a turn-key racer or the individual parts could be ordered separately. YB parts included: pistons/rings, camshaft, valve springs, racing ignition coil, two lengths of racing megaphones, alloy rims, tachometer option, racing seat, footpegs, starter delete and stator/rotor delete options and even pre-drilled fasteners. CB92Rs were capable of nearly 85 mph at 11.500rpms.

In 1962-3 Honda offered the CR93 production roadracer and a handful of "street bike" versions. Few of these made it to the US, but they were popular racing machines in Japan and the UK. These bikes were DOHC, 4 valve powered with gear-driven camshaft drives, capable of approaching 100 mph.

Honda made huge headways with their 125s, eventually on the world GP stage, however their first efforts in 1959 were a bit under the competition’s levels of achievement. The RC141 was a 44x41mm twin with 2 valves per cylinder, featuring a bevel-drive system to drive the camshafts.  It was quickly replaced by the 4 valve per cylinder RC142 at the IOM races. Honda actually used CB92 bikes as trainers for the fresh-from-Japan riders who had never seen the IOM course before.  It was said that the bike actually arrived with knobby tires fitted, as used on the Mr. Asama race course, which is made of volcanic cinders. Honda quickly fitted proper roadracing tires on their bikes for the rest of the events, but the first bikes all had leading-link suspensions at the front end, which lead to rather poor lap times. Honda did achieve a team prize for their 6-7-8 finishes in their first attempt at the IOM course, however.

Honda returned in 1960-61 with RC163 and 2RC-163 models, still DOHC 4 valve twins with 6-speed transmissions. By 1963 Honda served up a 125cc four cylinder model RC146, followed by 1964 2RC-146 and 4RC-146 models with 7-speed transmissions. In 1965-66 Honda dropped the big 5-cylinder, 8-speed bomb upon the 125cc class and won championships easily. These engines revved to 22,000 rpms and were capable of over 125 mph.

Honda left the world motorcycle racing stage in 1967, as they concentrated upon F-1 racing and the manufacture of automobiles and other automotive equipment. The next “factory” racer models to become available to a select few in the US were the CR125 Elsinore-based MT125R racers. The first generations had the same mechanical front disc brake and used a fairly stock CR125M engine with a special close-ratio gearbox. Feather-light, they could eclipse 110-mph if you could keep them on the boil. Later MT125R2 models were equipped with a water-cooled top end and hydraulic disc brake on the front wheel. These bikes were raced extensively in the late 1970s and into the 1980s. Eventually, as Honda re-entered the world of roadracing with their new NSR250 and NSR500, the 125cc class became the place to learn your roadracing craft, so Honda tooled up roadrace -specific RS125/NSR125 machines for world-wide distribution.

Dual-Sport/Off-road models
Honda offered a different set of “YB” racing parts for the CB92s, which created a “Scrambler” version of the 1960-62 streetbike. Dave Ekins, famous off-road racer in the 1950-60s, successfully raced a CB95 version of the bike in off-road competition; however it was eventually disqualified because it wasn’t a model that was officially sold in the US. That was Honda’s only 125cc-sized racer in the 1960s.

Honda broke new ground with 2-stroke CR125M Elsinore MX racers and the MT125 Elsinore street version, starting in 1974. This was Honda’s first departure from the reliable, but heavy and underpowered, four- stroke singles, which could never make the same kind of horsepower that a two-stroke single of the same size can generate.

Honda offered Dual-Sport and Trials 125cc versions of these early singles in TL125, CL125, SL125 and XL125 models.  Ironically, the SL125s were offered as early as 1971, while the street models didn’t arrive until two years later. The early XL125 models were pepped-up with higher compression pistons, upgraded camshaft, larger valves and a 24mm carburetor. The 1979-1985 XL125S models featured a slick 6-speed transmission. The TL125s, offered for just 3 years, spanned the transition of one-piece to two-piece cylinder heads, as did the other versions. TL125s were specifically designed to go SLOW, so they were detuned and setup for slow speed riding and low-end torque for Trials events.

By 1985, the four-stroke 125cc Honda singles had died out, in all of their variations. There was a NX125 offered from 1989-92, but these little dual-sport machines sold poorly, at least in the US.

You can’t buy them here, in the US, but the 21st Century has brought bikes like the CBR125R, water-cooled, SOHC, 2-valve, four stroke single in a cool sport bike chassis, with fuel injection! So, I guess after 58 years the concept of the “Honda 125” will never die after all.
These are just the highlights of the 125cc Honda series. I know there are many, many other 125cc models, sold in specific countries/markets which I have never seen or heard of before. In countries where 50cc bikes rule, a 125cc model is a “big bike” to those enthusiasts. Long live the Honda 125!
Bill “MrHonda” Silver

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