Honda made thousands of 125cc Benly and Benly Super Sports in the 1959-64-era. Despite the outward appearances there were numerous changes to the engine’s internals, including a half dozen crankshaft types and variations, which finally settled down by 1962 into a final part number, at least for the ones with a center main bearing.
Chassis types were based upon the C92 (actually starting with a C90 model w/o electric starting in 1959) with C95/CA95 (154cc engines), CA92 (1959 only), CB92 (1959-64), CS92 high-pipe Sport models and some more pedestrian C92s with unsupported center main bearing designs and rotary gearbox shift patterns. CB92s went to all countries with that model name, but Benly models coming to the US received an additional “A” in the model nomenclature; CA92 and CA95.
In Japan, various Benly-styled machines turned up in the mid-1960s using a look-alike engine style, but with entirely different parts installed. The C92-95 engines had “side camchain” engines designs with the camshaft driven off the left end of the crankshaft. When the 160 replacement engines came out for the CA160 models, the camchain drive was in the center of the crankshaft/crankcases. In 1966-68, the new generation 125 twins were released, still in pressed-steel frames, but with telescopic forks, instead of the earlier leading-link designs. The engines, however, continued to use the side camchain design, but all of the part numbers were 230 code-based, instead of the earlier 200-215 Benly types.
This 230 code bike was designated a CD125A. From that basic architecture sprang the 244 code SS125A Super Sport and the 243 code CL125A Scrambler 125 models, which were sold in the US, during the 1967-68 period. Honda was suffering some considerable financial hardships in the mid-1960s, with warehouses bulging with unsold inventory, which begs the question; “Did the US really need another pair of 125cc twins, while they were trying to sell the S90/CL90, CA160, CB/CL175, CB/CL450, leftover 250-305cc models and new CB/CL350s at the same time?” Apparently SOMEONE thought they would be a good fit! The US was spared the base model CD125A machines, with their carry-over Benly styling, but the CL/SS125As were offered in several colors and full support of the factory and AHMC. These small twins were the first Honda models to use the new CV (constant-velocity) carburetors, of which only one was placed on each of the single-port cylinder heads. The bikes came with a 4 speed transmission and seventeen-inch wheel sizes. Electric starters were a non-starter on these bikes, which helped keep the weight down to a manageable level.
In some markets, beyond the US, there was a very trick version CB125K3 model, using the same basic 230 code design engine, but with a tubular frame, dual-carb head and 5-speed gearbox setup. While the 5-speed transmission should go into the 4 speed cases, the dual carb head and intake parts won’t work with the pressed-steel frame design parameters. It really is a CB175 chassis with a 125cc engine transplant, one of numerous models which were never seen in N. America. Likewise, in Japan a 125cc version of the CB200T exists, which again was never shared with the US market. The SS125A and CL125A models shared the same basic chassis components (on 17” wheels), but differed in cosmetic items, including the seat, fuel tank, handlebars, fenders and exhaust systems.
In the past week, a friend’s original CL125A came down from Orange County, along with a 1965 CB77 for some tuning and general maintenance. The little 125 Scrambler only shows 6700 miles on the odometer and still carries the original front tire. The maintenance request began with a valve adjust, camchain adjustment oil change and general tune-up. While going through the valve adjustment and camchain adjustment steps, I came to the discovery that the camchain adjuster screw didn’t seem to be connected to anything inside. The screw went down several turns and then back up a number of turns without feeling any kind of resistance or contact with the camchain tensioner mechanism. My experience with the early Benly models is that they were designed with a wedge shape, which pushed the spring-loaded tensioner away from the chain when the screw was turned clockwise. Once that is felt, you just back the screw out enough to where it begins to feel loose again, then down a quarter turn or so. These newer versions had three rollers, instead of two and the tensioner pressure came from a combination light spring and hydraulic oil pressure which pushed a piston upwards against the camchain tensioner adjustment arm. It might have been quicker to refer to the online diagrams to get a refresher on how the CL125A tension system worked, but I decided to just dive in knowing that something serious must be wrong! Other than loosening some tight factory-installed Phillips screws with the usual impact driver, the engine is pretty easy to disassemble on the left side. Being a Scrambler means that that the exhaust pipes are always going to be in the way of some phase of maintenance. Rather than completely remove the exhaust system, I just loosened up the exhaust flange nuts a few turns, disconnected the rear muffler mounts and let the system float on the bike.
I was able to access all the engine case screws and remove the covers by just pulling up on the muffler system a few inches. The rear sprocket cover is only held on with 2 screws, but it has to be in place to retain the clutch cable joint, which is half installed in the forward cover and half in the back one. The dyno cover is held with just three screws, exposing the point plate and the end of the crankshaft, which carries the spark advancer. The whole system is very reminiscent of the early Benly designs, but somewhat more streamlined and efficient. Removing the stator gives access to the rotor which needs a special tool to pop it off the end of the crankshaft. All of my OEM Honda puller tools are too large, as the thread size is 14×1.5mm, instead of the 160-450 size of 16×1.5mm. Fortunately, the front axle from a CB77 is just that 14mm size and I keep one or two around here just for that use as a rotor puller tool.
With the rotor popped off, you see that the rotor was indexed to the crankshaft snout with a tiny dowel pin instead of the customary woodruff key. It is so small that you don’t have to remove it to get the inner case off the engine. The seal slides right over the end of the pin without causing damage. Once the inner case cover is out of the way, you can view all of the camchain tensioner components. The adjustment screw can move through a wide range of travel without touching either one of the tensioner arms. That is what I felt, but didn’t realize that turning the screw counter-clockwise far enough will engage the upper arm of the tensioner. Basically its job is a stopper to keep the tensioner from retracting too far back when the engine has stopped. The hydraulic piston only pushes up with force when the engine is running. A light spring helps keep the piston up in position, ready to go back to work when the engine fires up again.
Nothing was terribly wrong with the tensioner, other than it was 48 years old and the original rubber texture had hardened with time and exposure to heat and oil chemistry. I happened to have a couple of new tensioners in stock and offered to install a fresh one in the bike. The owner is very fond of the bike and wants to keep it up as much as possible, so he agreed to have me install the part. The tensioner assembly is centered on a circular base, which can rotate on the engine case bosses. There is a three screw retainer system to keep the tensioner secured to the engine, but allowed to rotate as necessary. These parts are located behind the camchain, so the cam bolts must be removed so the sprocket and chain can drop down far enough for the tensioner to slip out around the end of the crankshaft and the new one to go back in the reverse order. With the outer case covers removed there is nothing for the stator to secure to, which carries the index mark for the ignition and crankshaft timing. The basic rule for Honda motorcycles is that the keyway lines up with the centerline of the cylinders. Sliding the rotor back on the end of the crankshaft enough to engage the locating pin allowed me to turn the crankshaft back and forth while the camchain and sprocket were reset properly. The camsprocket has a small “o” stamped into the edge which is supposed to be aligned with the 12 o’clock position of the pistons. Basically you can draw a line between the center of the crankshaft snout, the keyway/locating pin and the “o” mark on the camsprocket, when positioned at the top. Because these are 360 degree firing crankshaft engines, you could install the camshaft in 180 degrees out, which just changes the opening sequence of the valves to the opposite cylinder. The engine fires both spark plugs at the same time and the cylinders just change phases between firing and overlap on each revolution. FYI: Most Honda twins up to 250cc are all the same configuration; 360 degree firing.
With all the tensioner pieces and the idle roller in place, it was time to button up the engine covers and fire it up. All went well until I went to check the ignition timing, using a small 12v test light (the bike has a 6v system, however). I looked up at the switch and the key was already in ON position. I touched the horn button and not a sound was heard… a dead, very dead battery. Removing the battery from the right side cover, I checked it with a voltmeter on the work bench. The reading was .4 volts, as in four tenths of one volt! The battery didn’t look particularly sulfated, but wet-cell batteries just HATE to be run down flat like this. I hooked up my 1 amp battery charger, switched it to 6volt setting and plugged it in. I went back to doing more work on the little bike, but periodically I would hear a “PING” noise coming from the shop. The charger worked as hard as it could but apparently one of the cells was shorting out, so the built-in circuit breaker would kick in and cause the pinging noises. It did this about every 4-5 minutes all morning long. Checking the voltage periodically, the readings rose from .4 to .8, then to 1.5, slowly moving upwards until it hit about 4.5 volts and that was the end of the charging efforts.
Truthfully, I didn’t expect to get much out of the battery at all, but put it back into the bike to see if there was any glimmer of hope that the bike would fire up on only 4.5 volts. The charging system is permanent magnet, so as soon as it starts to spin, it tries to build up voltage and send it along to the rectifier, which converts AC to DC volts and tries to charge the battery. I turned on the key and kicked and kicked and kicked… nothing! Then I looked up at the gauges and saw that the turn signal switch was pushed over to the right side selection which lit up the indicator light dimly. That is a BIG power draw for these little bikes. Switching the turn signal switch to OFF and kicking the bike one more time yielded a big roar and the engine spun itself up happily to a high idle speed. The neutral light glowed a little bit brighter, but subsequent voltage checks at the points only verified that the bike was running along on 4.5 volts being fed to its 6v coil.
You have to be careful running the engines with a dead/dying battery and running the bike off the charging system. The battery is the electrical load for the charging system output, so when it can’t handle the charging current, the excess goes out to the light bulbs that are illuminated and they often go very bright then burn out from the excess power in the system.
As mentioned, the carburetors used on these bikes are a CV-style which was new to Honda back then. This tiny fuel mixer has a rubber diaphragm connected to the slide by a plate with three screws. The throttle arm, on the top carburetor cover, presses the diaphragm down against a small plastic button. Unlike later CV carburetors, there is no separate throttle plate. The choke is a butterfly design which does have a through shaft across the carburetor body, but that’s it! As the throttle cable lifts the top cover arm, the slide begins to rise up and expose more and more of the carburetor throat.
The biggest problem with servicing the carburetor is that you cannot remove it from the bike without loosening up/removing the engine mounts and tipping engine forward enough to clear the two mounting studs. The inlet of the carburetor is surrounded by the air filter tube flange, which is force-fit into the frame, itself. There is no flexibility or room to back the carb off the studs and off the bike, as designed. I went ahead and tipped the engine forward, removing the carburetor and then removed both of the studs, as well. I found some short 6mm bolts which, were just the right length, to angle into the flange holes and capture enough threads in the cylinder head to hold it all securely in place. I replaced the 230 code 32mm carburetor flange o-ring with one that is designed for a Honda Dream (28.5mm) and it was a perfect match, despite different part numbers.
The carburetor parts on these bikes are very tiny. The main jet holder requires a 7mm wrench to loosen it up. Main jet size is #95 with a #35 idle jet and a 21mm float level. The main reason for pulling the carb was that it was seeping fuel past the float valve overnight. I checked the float level setting first which was right on the money. The float didn’t seem to be “sinking” from pinhole leaks, but the float valve needle appeared to have a little bit of a ring worn around the tapered tip. It is so small that I could barely see the surface of the needle tip. Nothing really stood out as an issue, other than the worn needle, so it went back together and was reinstalled with its new hardware setup.
The air filter design is another piece of work… The long air cleaner tube is fitted around the opening on the frame in front then extends into and through the backbone of the frame. A metal bracket secures it to the frame with two bolts, and then the filter assembly, with the inlet piece, gets pushed down inside the filter tube into an indeterminate final resting point. Apparently, if any of the pieces are not properly aligned the bikes will run poorly. I pulled the air filter element out as far as I could, but it seemed to be jamming up inside the frame/filter tube and I was unable to extract it successfully, at first. Finally, I felt that to remove the filter, the rear fender would have to be loosened up and dropped down on the forward mounts. This action did give access to the filter components, which are tightly crammed in place and the rubber seal area at the back of the air filter tube becomes oval when you remove the filter, making it very difficult to reinstall again.
It is hard to fully evaluate the running condition of the bike, due to the limited voltage available to the ignition coil with the current 4.5volt battery situation. The bike will go back to the owner as-is with instructions to install a new battery then test the bike fully, afterwards.
With only a 4-speed gearbox, the bikes are geared low and get buzzy very quickly as you attain road speed. They are comfortable enough at about 50 mph, but sound strained much beyond that. Little twins such as these are capable of turning up 10,000 rpms in some applications, but the limited breathing of the single carburetor restricts any great power output.
It is interesting to be able to re-experience these little twins, which had only a two-year appearance here in the US. The other CD125 variants thrived in Asian and European markets for a number of years, but that was the end of the road for the 125cc Honda twins in America. The 125cc street bike market in the US is very limited, but AHMC did offer the CB125S single-cylinder models from 1973 up into the early 1980s, but with limited sales success. Honda completely remade their 125cc twins in 1977, with the introduction of the CB125T, which arrived with a 180 degree crankshaft firing engine, capable of 12,000 rpms, fed by dual carburetors and a 5 speed transmission to complete the 80 mph out-of-the-box package. Those bikes never made it to the US, except as some MSF training machines in some areas. The engine package was extremely robust and began to grow and grow in displacement in steps from 185 to 200 and eventually to 250cc. In the US, they were known as Twin Star 185-200s, then CM250s and finally as the Honda Rebel and Nighthawk 250s, which sold in the thousands of units and still available today. That was a major leap for a tiny twin, wasn’t it?