Wednesday, December 30, 2020


Often, when you discover a vintage Honda 250 or 305cc twin available for sale, it is lacking the title or other necessary documentation. Depending upon the state or country's requirements, you will find it necessary to "create" some paperwork for registration purposes. The first step in this process is to determine the correct year of production.

On early-'60s (1960-64) Honda 250-305cc twins, this can be pinpointed accurately, using the frame/engine serial numbers, found at various locations on the bike. You will notice that Honda's serial numbers carry a letter (or two), followed by a number (i.e. C or CA77, CB72, CL77, etc.). The "72" designation (as in CB72) denotes 250cc models, while the "77" designation signifies 305cc models (for instance, CL77). All pre-1961 (C70-71 & C75-76) engines were "dry-sump" design (separate oil tank). After 1960, the C/CB/CL 72/77-series engines were all of conventional "wet-sump" design (all oil carried within the engine).

Honda's frames were classified as either: C "Dream" (touring-style); CA or CE (US-only versions of "Dream" touring models); CB, "Super Sport" road models; CL "Scrambler" (dual-purpose); CR (production roadracing models); and CS, the "Dream Sport" (usually featuring high-mounted side pipes). The C (or CA, CE or CS)-series "Dream" models have stamped, sheet-metal frames, forks and swing arms, riding on 16" wheels (except CE71s) and equipped with "leading-link" front suspensions. All other models (CB and CL) will have tubular-type frames and swing arms, fitted with 18" (CB) or 19" (CL) wheels and conventional, "telescopic" front forks.

For 250-305cc street bikes, built before 1965, the identifying process is relatively easy. In the late '50s and early '60s, the year was often coded within the serial number (i.e. C71 59 12345); the center numbers denoting the year ( in this case 1959). Later, the first digit of the 5-digit frame (and 6-digit engine) number was used as the year code (i.e. CB72-11123, a 1961 250cc Sports model). Here's an overview of the three most popular models:

CB models: The CB72/77-series (known as 250 Hawks or 305 Super Hawks) were numbered as follows: '61-63, first digit in frame (five digits in '61-62; and six digits in '63) and engine serial number (all six digits) was year of manufacture (i.e. CB72-1XXXX; CB72-2XXXX or CB77-31XXXX frames and CB72E-11XXX; CB72E-21XXX or CB77E-31XXXX engines).

In '64, frames and engines both started with 100001 (both six digits) OR 4XXXXX numbers. The 1965 models started with 1000001 (seven-digit frame and engine numbers) and continued in that fashion. Generally, the frame and engine numbers are within 150 numbers of each other or less (often within 15 numbers), if they are the original factory pairing. One possible reason for the mismatch is that Honda would pull engines from the assembly line and dyno-test them for durability, performance, and any design/manufacturing flaws. Interestingly enough, I once owned a '64 CA77 which did carry matching 108106 frame and engine numbers; a very rare occurrence in my experience! I have noticed that, in general, the '64 engines and frames are more closely matched than for other years.

Getting back to the CB's, there are several variations, other than the "regular" Hawk/Super Hawk versions, but they were never sold in the US. The vast majority of CB-series bikes all seem to be normal Type 1 (180 degree crank) engine versions. Then, you may also find the odd CP77 frame, which may or may not be a "Police version," (which is usually called a CYP), as well as a CBM72, which has high bars, turn signals and a Type 2 (360 degree) crankshaft. The actual CP77 Police models had a different second digit in the serial number to separate them from the non-Police CP77s.

There are also "domestic" versions of CB77s with Type 2 engines. (I owned an original '62 model carrying CB77E-260474 and CB77-62-60453). Deviations from the "normal" numbering sequence usually denote models for specific countries or special applications. Genuine CYP77 Police bikes are all white and have a single, round speedometer, rather than the oval, dual speedo-tach gauges of the other models. Some Police models had 17" wheels, front and rear. Police versions have crash-bars, turn signals, solo seats, a rear rack, special lever brackets for the siren controls, patrol lights, and that great big, screaming, cable-driven (off the rear wheel) siren.

From 1965-on, there is no definitive break between the years 1965, 1966 and 1967, that I have been able to discover. Although the chrome-fendered CB models, with the "oval" tail light, were introduced from frame number 1056084 and onwards, which was at the end of the production run in 1967. The TYPE 2 aluminum fork, which appeared at CB72-1005228 & CB77-1030130, seems to be found on all '66 and later model year US bikes, according to their wiring harness tags. However, the "domestic" CP77 models featured this fork design in '65, a year before the US models received theirs. Total production for this period ('65-'67) was 56,432 (frames), so you can roughly divide that figure by three, yielding about 18-19,000 per year. If the type 2 fork bikes were all '66 models and later, then they made 30,130 1965 models and only another 26,000 more in 1966-67 combined. CB77-1056432 was the last CB77 made, in 1967.

Early models of the '61-series CB engines (and C/CA models) used a "rear breather" crankcase design and the first 280 bikes had a single-leading shoe front brake. There are three different crankshafts, three transmissions, two series of pistons, three series of camshafts, four different MPH speedometers (running in two different directions), early steel and late alloy fork assemblies, three different taillights, three different fork crowns, etc. etc. for the CB-series bikes. This is why you must always check your engine and frame numbers before ordering parts! At a distance, they all seem to look alike, but there are major differences between the years.

Sometimes, the original engines have been swapped with other CB or sometimes CL engines. I have even seen CA engines in some CB chassis! CL engines are not equipped with electric starters but can be retro-fitted with CB or CA starter motors and starter clutches, for CB installations. Or the CB engines can be relieved of their starter motors and then installed in a CL chassis! CHECK THOSE SERIAL NUMBERS CAREFULLY if you are ordering parts or doing a "correct" ground-up restoration!

CL-72 models: CL72's (250 Scramblers) were made from 1962-66, with CL77's being produced from 1965 through 1967. Bikes built through 1962 had 5 digit serial numbers (frame) and 6-digit engine numbers. Again, the first digit in the 5-digit series (6-digit in '63) is the year of manufacture. Thus, a CL72-21977 (example) is a 1962 model. It got confusing in '64, with an early bike series starting with CL72-1100001 thru 1109459 numbers, followed by CL72-4000001-4003437. The CL72-1000001 and-up numbers (all seven digit) were '65-66 models.

CL 72 models made after CL72-1008851 bikes had alloy Type 2 forks, big brakes and steel fenders and were made in late-1965, probably when the late-'65 (or probably '66) CL 77 models received their alloy forks and big 8" DLS brakes. CL72-4001597-4003196 and CL72-1000001-later models had rear brake cable anchored to the frame, instead of the cable receiver on the end of the swing arm bolt, which was seen on all earlier versions.

All 250 Scramblers, built through CL72-1107409, have "double-eye" shocks and a matching swing arm. Shocks with clevis ends on the bottom were used, thereafter, on the CL72's and all CL77 models. The slip-on exhaust silencer seems to have been introduced with '65 models. Later versions were welded onto the upper pipe. There are at least three sets of exhaust pipes/mufflers for the CL-series machines.

The CL77s: The 305 Scrambler models, CL77-1000001 to 1014495 were built as '65 models and were equipped with CL72-style steel forks and the same "small" 7" SLS Bikes after CL77-1014495 had 8" DLS brakes, similar to the CB77, but the front wheel is mostly derived from CB450 parts. The chrome fender bikes with the "oval" taillight started production from CL77-1043098 ('67 models). The "CB450" headlight, with bulb screw adjuster, began with CL77-1042143. From CL77-1033482, the rear shocks used an improved rear shock cover with a larger collar design. Longer exhaust heat shields were used from CL77-1046212 onwards.

The rubber-mounted seat and cushioned front footpegs were introduced from number CL77-1033482, along with an appropriate frame change to accommodate the redesigned forward seat mount. Front fenders and stays were changed, with the introduction of the Type 2 (aluminum) forks at CL77-1014496. A modified crankshaft with larger splines was begun at CL77E-1043132.

C/CA "Dreams": The C/CA-72/77's serial number pattern seems to be much the same as the CB-series. Of course, ALL C/CA engines are Type 2 (360-degree crank) engines. While "Dream" frames often seem to have no serial numbers, they are normally found in a location on the left side of the frame, behind the engine, below the swingarm pivot, and next to (sometimes under) the footpeg mounting bracket. It is an obscured area, often covered with grease and dirt. Many U.S. CA77's are stamped CA78, but the engines are all marked CA77. '61 and early-'63 models had different styling on the tank and chrome side panels, as well as a myriad of other smaller details concerning the handlebars, cables, fenders, seats, plastic side covers, etc. The CA78 models are often called “Late Dreams.” “Early Dreams” differed between the 250 and 305 models, mostly with the fuel tank designs.

All Dreams, through 1965, used a tall, thin, wide 12v battery (6v on dry-sump models), which was then superseded to the CB-type battery. The frame's battery tray, tool tray, and side cover were all modified to accommodate this design change. Seven-digit serial numbers commenced in 1965 on Dreams, too.

Almost all models, sold outside of the U.S., had turn signals (winkers) factory-installed. There are several different versions of "winkers," which correspond to the legal requirements of different countries. Sometimes, you will find 250-305 models registered as '68-69 models, but remember that they ceased production in '67, to make way for the CB/CL 250-350 models introduced in 1968!

The final way to date most complete, original bikes (that haven't had a wiring harness fire, modification, or some similar misfortune) is to check the harness between the steering head and the battery connectors (usually somewhere under the fuel tank) for a small white tag, attached to the outside of the harness wrapping. It will usually show both the part number of the harness, often including the model and THE DATE! It is the date of manufacture of the harness, but almost always corresponds to the date of the bike, too, but we have found exceptions to that rule, as well.

Well, so much for a "brief" history of dating Honda "big twin" motorcycles, produced in the early to mid-'60s. Starting with the 1970 models, U.S. regulations required manufacturers to show the month/year of manufacture of all motorcycles. This ID tag, which includes the frame serial number is usually found on the right side of the frame's steering head. Since 1981, the 17 digit VIN codes have been standard on all motorcycles. They can be decoded too, but that is another story.

Bill Silver (aka MrHonda)

Sunday, December 13, 2020

The Classic Honda used bike minefield… CB/CP77

The line from Forrest Gump that goes, “My mom always said life was like a box of chocolates. You never know what you're gonna get.” certainly applies to prospective purchases of vintage Honda motorcycles.

Unless you are buying from the original owner who has all the service records and a list of mods or damage repairs, you can never really be sure about just what you will find when you set your eyes on that rare bike that you have been lusting for during the last few years.

Case in point: I was helping a friend try to track down a black Honda CB77 Super Hawk to match is original black CB160. I had recently helped him market his CB450 Black Bomber so now he was hunting a black Super Hawk. I had sold a couple of really nice bikes in the past two years, but it seemed like very little was out for sale in the past few months. Hoping to avoid a blind purchase of some bike that was far, far away, an “opportunity” passed though my searches that appeared to be the black CB77 that my friend was seeking right here in San Diego County.

In the photos, it certainly appeared to be a “flat bar” CB77 of about 1964-65-ish vintage, but it was listed as a 1965 CP77 instead. The production CP77 (non-Police bike) models were never sold in the US, but they seemed to have been offered in Canada back then and a few of them migrated down to the US over the years. The model causes confusion as it might be considered the “street bike” version of the CP77 (actually CYP77) Police model. Again, a few Police models did go to Canada, but never to the US. The non-Police models look like standard CB77 Super Hawks, except that they have very high handlebars, turn signals, a sidestand, solid footpegs and the tail light that was only seen on the 1961 CB72-77s in the US.

Looking at the photos of this bike, it was obvious that the handlebars had been changed, the original turn signal switch was missing as were the rest of the winker parts. The side stand was not present and the tail light appeared to be the generic CB72 taillight used on 1963-66 models. So, in essence, the bike was reconfigured from the original CP77 roots to an early-style CB77 look.

Some of the current owner’s history was shared in that he had reworked the front forks due to some accident damage, had given it a good tune-up and may have replaced the tires. Unfortunately, the tire choices were 3.25x18 front and 3.50x18 rear which will ALWAYS upset the bike’s ability to stay steady on the centerstand.

I was requested to check the bike over prior to the sale transaction, which took me 50 miles from home. The bike presented itself as an unrestored model, which had a few dings and chrome pitting, but seemed overall a solid base to work from for someone who was willing to spend some time and money to get it back towards original condition again.

I started the engine, which sounded healty and firing on both sides evenly. In retrospect, I should have taken it out for a quick spin to check it for clutch slippage and/or clutch release issues.

After some wrangling, the owner and buyer made a deal and we loaded the bike into the back of my Tacoma for drop-off in Solana Beach, CA. By the time I returned home there was a message about what to do with the bike to get it serviceable and closer to stock CB77 shape. Obviously, the tires were top on the list and replacement rubber in the stock 2.75x18 and 3.00x18 sizes were ordered up.

The next question came up about how the steering lock works. At first the key was sticky and the lock wouldn’t move properly. With a few squirts of graphite lube, the steering lock was working fine, but the place where it was supposed to lock into was not present. A close-up photo revealed that the whole steering lock portion of the frame was cut/sheared off, perhaps in an accident. I can’t say that I have ever seen this happen before on a Super Hawk, as the steering stops for the stem contact the frame down behind the steering lock bridge portion. It was a mystery and a problem not easily remedied.

After a batch of parts had arrived, I arranged to swing by the owner’s home and dig into the project, starting with changing out the tires. The tires dates were back in the early 2000s and their oversizes caused extra difficulty in removing them from the rims. I started with the rear tire and once it was removed, there was a good bit of rust corrosion in the rim bead area and around the spoke holes. I knocked off the worst of it and wire-brushed the loose bits. I wrestled the new tire back on and prepared to install the wheel again, but saw signs that the ends of the cotter pins on the rear sprocket castle nuts were hitting something. There were signs that the cotter pin ends had been hitting the inside of the chain guard bracket, which also showed signs of being rewelded previously.

An even closer look revealed that the rear shock bolts had been installed backwards so the thick outer nuts were very close to the sprocket nuts. The shocks required removal and a 180 degree turn on the bottom to get the threaded portion of the lower clevis set properly, so the shock bolts, which have thin heads, were installed with them pointing outwards. The previous owner had commented that he had to put a longer chain on the bike to allow the rear wheel to be moved further back enough to clear interference with the forward edge of the rear fender, next to the swing arm. That sort of made sense, but then I discovered that the rear sprocket was stamped 32 instead of the stock 30 tooth markings. The stock 94 link chain had been included with the bike’s spare parts, but obviously wouldn’t work with the big tire combo.

I had brought a spare pair of new aftermarket chain adjusters to help brighten up the rear axle area, but one of then turned out to have stripped threads for the adjuster bolt. It is amazing how much time is spent sorting out all the little issues like these when you are wrenching on an older Honda bike with a little known history.

Once the rear wheel was reinstalled, it was time to move onto the front tire replacement. The first thing to notice was that the pinch bolt for the left front axle case was an Allen bolt, instead of the normal bolt with a 14mm head. Secondly, the bolt was loose in the threads. The bike had to be jacked up in front off of the starter motor, but the bike was also supported by a 2x4” board beneath the center stand feet to give the bike enough room to pull the over-sized front tire out of the forks and front fender. I had to remove one of the fender stay bolts to allow the wheel to clear the the fender’s cable stays. Apart from pinching the inner tube (there was a spare, thankfully), the front wheel went back together okay, except for installing a few front brake cable. The cable adjusters were mostly used up in getting the brake to adjust properly, which turned out not to be worn out brake shoes but the brake linkage arms had been installed one spline off from where the punch marks were shown. The wheels will be coming off again in the near future so the fenders can be removed and repainted, so the brake cam/arm issues can be addressed then.

The last few jobs for my 4-hour stint included an oil change, change the spark plugs and check the ignition timing. The first two tasks were easy enough but the last one brought a shock to me when the dyno cover was removed…

Instead of the typical CB72(L) rotor marks on the face of the rotor, I was faced with C72 marks which can only come with the use of a Dream or Type 2 engine CBCL engine. Beyond the surprise of seeing the wrong rotor installed, instead of a central rotor bolt to attach the rotor to the crankshaft there were two nuts, double-nutted on a stud! I have NEVER seen this adaptation done to a CB77 engine before or any other one, which leaves one to wonder, whether the end of the crankshaft threads were damaged previously and this was some kind of creative repair to keep the bike on the road.

The rotor had some black marker hash marks 180 degrees from the only stamped T and F marks on the rotor, which appeared to be properly set. I hooked up a dynamic timing light to the ignition and verifed the right side marks first. Then I used the black line mark as a hopefully accurate mark to set the left side ignition timing. The marks showed that the timing was retarded a few degrees, so a small adjustment was made to correct the error. The engine idles evenly and sounds like it has good compression. There are no signs of smoking, but there is no known history of what has been done to the engine beyond what has been discovered.

A quick ride around the neighborhood revealed that the transmission didn’t want to shift back into neutral when the bike was at a stop in gear. This is almost always due to someone removing the thin wire retainer rings from the clutch hub. The retainer wires help hold the first few clutch plates on the hub, which helps the rest of the clutch pack separate and release it’s grip on the transmission shafts. When the engine torque is removed from the transmission shafts, the shift selector can do its job of selecting whatever gear you wish, including neutral.

So, the next few upcoming hours will include removing the clutch cover, inspecting and cleaning the oil filter, checking what appear to be excessively strong clutch springs, looking for missing retainer springs and then popping in a new shift shaft seal while the cover is off.

If that doesn’t reduce the amount of clutch lever force currently experienced, then the kickstarter cover will be removed and a new clutch adjuster will be installed to reduce the amount of thread slack between the adjuster and clutch lifter arm threads. Reducing the slack translates into increasing the amount of clutch pushrod travel which separates the clutch pack more completely.

$100 worth of gaskets, seals, chain adjusters, clutch springs and a clutch adjuster have been lined up for the next round of repairs, hopefully the last for awhile.

Round Two….

The priority task was to address the clutch release issues, so the right side exhaust was removed to allow the kickstarter cover to be taken off to inspect the clutch adjuster threads/slack. Pulling and pushing the clutch lifter arm in and out of the clutch adjuster showed excessive slack/play between the two parts. The clutch adjusters are made of aluminum so the coarse threads are eventually worn down from repeated cycling of the clutch while riding. This bike was showing 10k miles and the parts looked original, so a fresh clutch adjuster was installed.

An unfortunate surprise when the kickstarter cover was pulled back was a splash of motor oil that had pooled below the crankshaft/starter clutch. Using a flashlight to check for oil trails, didn’t show anything that was really active on seals that were installed in the cases. So, that left the little seal that installs in the center of the starter clutch hub as the probable cause. Ordinarily, I would pull the rotor bolt and use the 16mm special tool to remove the rotor to check the starter clutch roller springs and the condition of the oil seal on the starter clutch hub. In this case, the C72 rotor that was looking back was being held in place by a stud and nut/washer instead of the normal rotor bolt/washer. As this was a house call visit, I didn’t have all the tools I needed to go further in this direction, so I had to wipe up the oil mess and leave it alone for the moment.

The new clutch adjuster was greased and installed, then the kickstarter cover reattached. Pulling the clutch lever felt about the same as before. So, the next step was to go to the left side, remove the exhaust system and footpeg/linkage to allow the clutch cover to be removed. The cover screws all came out easily and the cover came off with the gasket intact for a change. Pulling the clutch spring bolts out revealed what appeared to be the “white springs” which are stock for 305s of that time-frame. That was puzzling, but pulling the the plates off and looking carefully showed the probable cause of the clutch drag problems. I was somewhat surprised to see that the oft-removed steel retainer wires, which hold the first few plates in place, were still in place.

While the friction plates looked normal for used parts, the steel plates showed all the signs of an earlier “stuck clutch” condition where the plates had been pressed together for many years of storage, then adhered together transferring some of the friction material to the steel plates. It generally looks like a combination of rust and friction material that is left behind when the clutch is jarred loose by running the engine with the clutch lever pulled in until the clutch plates get unstuck.

When this approach is used, the leftover material on the steel plates keeps dragging against the adjacent plates which prevents a clean release of the clutch pack and causes difficulty in finding neutral when the bike is in gear and stopped at a light or stop sign. I had brought a set of steel plates that were NOS and rather than try to clean the old ones, we popped in the new set, reassembled the clutch plates and springs and then checked the clutch release function. You can watch the clutch separate by pulling the clutch lever in and kicking the engine over. When the clutch releases, you can see and feel the disconnect between the engine and transmission. It appeared to be working correctly, so we put it all back together again, refilled the crankcase and fired the engine back up again. Even driving the bike just a few yards in gear, then selecting neutral yielded the little red neutral light lighting up with ease.

So, the clutch release issues were finally solved and the bike is now driveable in traffic without struggling to get the transmission into neutral with relative ease. The total labor time ran close to 3 hours in wrangling all of the parts for the clutch release problem. That’s good news for now, but that oil leak is still present and will need to be addressed sooner than later. The owner wants to remedy the loose fork covers by replacing the little rubber ring packings that sit down inside the fork rings. That requires removal of the front wheel, fender, handlebars, fork bridge and all the related parts. So, that is the next round of labor to hopefully complete the major repairs and complaints for this 55 year-old classic Honda Super Hawk.

Round Three

This time, we had to resolve the mystery of the C72 rotor mounted on the end of the crankshaft with what appeared to be a stud instead of the conventional rotor bolt/washer that screws into the end of the crankshaft. I sourced a new CB72 rotor from my dwindling parts supplies, loaded it with new springs, caps and rollers ready to install, along with a seal kit to remedy the previously discovered oil leak issues. I brought a 3 jaw puller to attempt the rotor extraction and once it was in place, a few hard turns of the tool’s shaft brought satisfaction as the rotor flew off the end of the crankshaft, scattering little starter clutch springs, caps and rollers around the floor. With the rotor removed, you could see that the oil seal for the starter clutch hub was half-way falling out, which accounted for the oil leak. The main crankshaft seal seemed to be holding up okay, so we just replaced the clutch hub seal with a new one and reassembled everything with the new rotor. The mystery of the end of the crankshaft was resolved when it was revealed that a bolt had been welded into the end of the crankshaft! I guess no one will ever know why the previous owner took that path of repairs, but the end of the crankshaft still runs true, so it is what it is and it is good enough for the future.


Bill “MrHonda” Silver