Coming through in the clutch… Honda 250-305 clutch history

One of the most confusing aspects of 250-305 engine repair is sorting out the numerous versions of the clutch assembly. I will attempt to demystify it here, if possible.

Honda began the new wet-sump engine series in 1960, starting with the 250cc Dream, then adding the 305cc version soon afterwards. In 1961 the CB72 and CB77 Super Hawks emerged from the factory, followed by the new 1962 CL72 250cc Scramblers.

Honda started with a light pull, conservatively-designed 4 plate clutch used in the first generation C/CA72 250cc Dreams.  In the parts books, you will see these parts with 259 part codes, which is the code for the 250cc Dream engine series. With the somewhat higher power output of the 305cc engines, the parts were upgraded to 266 codes for the clutch pack and the primary chains. Yes, there were three different parts numbers just for the primary chains, starting with 259, then 266 and finally the 268 code part for the CB72.

The thick 5mm friction discs of the 250s, coupled with very light clutch pressure springs resulted in clutch wear and failures fairly early on in the production cycles.

From the 1960 Dream parts books we see:

The 250s had four thick friction plates and four steel plates. The center hub had no grooves for retainer springs. Early pressure plates have been seen with small metal pegs inserted around the edges with tiny coil springs attached, which helped push the clutch assembly apart during disengagement. The 305s had five sets of thinner plates. One set of clutch springs sufficed for both versions, at first. Apparently clutch wear and failures became common, so a new set of clutch parts were designed for the Dream engine applications. Notice there are two clutch outer part numbers. The first is a solid mount rear chain sprocket style and the 010 version was the improved “cush drive” model. The inner clutch hubs came in two more types using the stopper rings, fitted into grooves machined into the clutch hub. Ring groove locations varied due to the differences in the thicknesses of clutch plate pairs which were being retained by the stopper rings. 

Clutch springs were offered in 259-000, 259-010, 266-000 versions, which became progressively stronger, as necessary. Clutch centers were offered in 259-000, 259-020, 266-020 and 266-030 for 250 and 305 models, respectively. The early model clutch friction plates were molded solid fiber material. As the clutch designs progressed, the 268-020 coded friction plates were made in aluminum-backed parts with the friction material bonded to the metal backing. Friction materials varied in thicknesses depending upon the application and number of plates used. Dreams wound up with either 5mm thick, 4-plate clutch packs or the thinner 4mm 5-plate combinations. The Plate “A” (first plate on the hub) was generally 2x the thickness of the other steel plates. Steel plates come in several thicknesses, so just the right combination of parts needs to be achieved to create the best possible clutch pack build.

What is important to remember is that no matter what combination of friction and steel plates were used to complete the clutch pack, they ALL had to have the same stack height when installed on the engine. If the stack height isn’t matching to OEM specifications, then the clutch release components inside the right side kickstarter covers will not have the correct geometry to effectively release the clutch pack when the clutch lever is pulled in. The clutch lifter arm must travel through a shallow arc, starting below horizontal plane and arcing upwards above horizontal. As the clutch lifter arm moves within the clutch adjuster (fixed in the kickstarter cover), the coarse threads of the two parts create a pushing motion on the end of the clutch release pushrod, which contacts the big ball bearing nestled deep inside the clutch lifter arm.

Many people have discovered sudden loss of clutch lever action, usually when the kickstarter covers have been removed for servicing or clutch cable replacement, due to the ball bearing dropping out of the lifter arm hole. The thickness of the ball takes up considerable amount of lateral play in the clutch release mechanism, so when it is missing it is impossible to adjust the clutch free-play using the cable adjusters or the clutch adjuster on the side of the kickstarter cover.

Scrolling down these pages to the CB72-77 clutch parts list, you will see that there was a 6 plate clutch offered, a 5-plate version using all fiber friction plates and finally the last generation 5-plate clutch using the metal-backed friction plates. Obviously, in order to accommodate a 6 plate clutch pack, all the plates needed to be thinner than the 5-plate set. The last generation CB72-77 (and CL77) used a clutch center with retainer grooves placed to allow the thicker plates to be installed and retained. The last of the steel plates had anti-warp notches stamped along the inside edges to help keep the plates flat when they became heated during aggressive operation. The Plate A is quite thick and has a beveled back edge to clear the clutch outer when installed. Late version pressure plates have angled drain holes to help evacuate trapped oil inside the clutch assembly.

There were three different clutch covers first due to a change in the shift shaft lengths, then the progression from “small hole” to “large hole” outer oil filter cover sizes. Remember to check your new parts against the old ones, when doing replacement of components.

CB72-77 clutch springs went through a series of part number changes from 268-000 for the 250s, followed by 275-000/010 for the 305s, then to the very stout 275-810 racing clutch spring. For most normal stock street applications, the 275-000 spring (equivalent to the 323-003 CB500 Four spring) works fine with stock clutch pack parts. These springs give a nice balance between light lever pull and sufficient pressure to prevent clutch slippage. Use of the later 275-810 springs will give the rider a very heavy lever pull experience, but does ensure that clutch slippage is pretty much non-existent.

When there is wear inside the clutch adjuster threads, there is a progressively lessened amount of clutch pushrod travel to disengage the clutch plates. The wear increases the amount of force needed to disengage the clutch to the point where the combination of heavy springs and worn clutch release parts can cause damage to the early version kickstarter covers. Later versions of the kickstarter covers were designed to move the clutch cable joints more forward, closer to the cover retainer screw mount.  Increased strengthening ribs were incorporated into the cover design to help prevent breakage which is especially common in the Super Hawks, which have forward-kicking kickstarter levers.

Well-lubricated clutch adjusters with minimal thread wear will enhance clutch lever pull efforts in a positive way. Heavy clutch lever pull effort is often a combination of dry and worn (and misrouted) clutch cables, worn clutch lever pivot bolts/holes and excessive clutch adjuster thread wear.

CA clutch parts list (1969 book):

                                                CB kickstarter cover... ready to install.

Final conclusions:

You cannot indiscriminately mix and match Honda friction and steel clutch plates and have a normal operating clutch on a 250-305. Steel and friction plates come in various thicknesses and designs.

You MUST use the clutch plate pack that matches the inner clutch hub retainer wire grooves AND use the retainer wires, as designed. These “stopper” wires are becoming extinct, so I have used picture hanger wire or very thin safety wire to use for the same function. Installation of the plain wire requires drilling an additional hole in the hub and securing both ends of the wire inside the hub where the stopper wire ends usually wind up after installation. If you leave the stopper springs out, you will have difficulty in selecting neutral when the engine is running and you are at a stop light/sign and need to release the clutch in neutral while you wait.

The best solution is to use the 1965-ish and later CB/CL77 clutch assembly, which includes the cush-drive clutch outer and the sturdy 268-020 friction plate sets. See photo below for comparisons to your clutch assembly. Remember if the clutch pack stack height is not correct, clutch engagement/disengagement issues will arise.

Using a CB/CL77 clutch is perfectly fine in a 250-305 Dream. You might play with using some of the lighter clutch springs to lighten the clutch lever pull, as strong springs are not needed for Dream applications. The Honda 425 code springs are the superseded parts for the Dream clutch springs.

Using Barnett clutch kits will not allow use of the inner hub stopper springs, so clutch release at a stop sign/signal light will be compromised. Barnett plates tend to drag when cold and the spacer plate they use to compensate for the changes in plate thicknesses will cause problems for street use. IF you are racing your bike and don’t care about street use, then going for heavy springs and heavy duty clutch plates may be the way to go, but you will have difficulty getting the transmission into neutral without the stopper springs in place.

Watch out for late model “shallow spline” replacement parts, used on 1966-67 models. You can use the shallow spline hub, crankshaft sprocket and countershaft sprocket on earlier bikes, but not the other way around. The OD on the shallow spline parts are the same as the deep splined parts, so it is the ID which causes conflicts when trying to use early parts on late shafts.

 Honda has superseded the 259/268 steel plates to 329 code parts from the XL350.

Bringing them back alive…

It was another week of bike wrangling at Casa de Honda as the month of April winds down. Recent sales included a 2015 Sym 150 Wolf (after the BAT sale of the CR93 tribute bike, a Suzuki GN400 and the 2400 mile Yamaha XS650). Most recently, I swapped out a mint condition 2013 PCX150 scooter for a non-running 299 original mile 2008 Honda 250 Rebel.

If that wasn’t enough, I spotted a survivor 1968 CL125A Scrambler in the local Craigslist postings, which had been on and off their site for a week or so. When I contacted the seller to find out about the basics like: Does it run? Is it registered currently? Are there any big problems with it? Etc..

The initial response was “I don’t know much about motorcycles.” Digging deeper in the communications, it appears that the bike was bought because it “looked cool” and it was a first motorcycle purchase for him. As I expected, it was a good 10-footer, but when you got close-up it became obvious that the bike was basically all original: cables, tires and body paint. The tank had been re-sprayed with some kind of close to Honda Silver color, but the rest of the Candy Blue paint was untouched, apart from the scratches, dings and general wear and tear that you would find on a 49 year old baby Scrambler.

Both bikes needed new batteries and fuel system maintenance. Despite the stinky green fuel that exited the petcocks, the carburetors were relatively easy to clean after wrestling them out of their respective chassis. These two bikes must be somewhere in the TOP 10 of “hard to remove” carburetors category. The CL125A carb is sandwiched in between the cylinder head intake port and the rigid air cleaner tube that flairs out over the opening in the frame. The only way that I could see to remove the carburetor was to take off the two 6mm nuts, then, using Vise-Grips, work the two intake studs out of the head, so the carburetor could slide sideways out of the frame.

The idle jet was plugged up and all the rest of the jets and emulsion tubes were cleaned and checked for open passages. This was Honda’s first attempt, that I know of, to create a CV (constant velocity) carburetor. The slide has a delicate rubber diaphragm secured to the top by way of a plastic plate with 3 tiny screws attached. In the middle of the plastic plate is a spring-loaded plunger which is pressed down by the carburetor arm which resides inside the top cover. While CV carbs on 350 twins from 1968-73 used a light spring to press the slides down in the carburetor body, the tiny slide on a 125 (remember this is a 360 degree firing engine with a single carburetor) is too small to control in the same manner, so Honda put a big heavily weighted spring in the top cover to push the slide down firmly whenever you let off the throttle.

While the diaphragm was probably original and felt/sounded very brittle, there were no holes or tears in the rubber, so it was gently reassembled and seemed to hold vacuum properly. The carburetor flange is sealed with a 32mm o-ring, which has been discontinued from Honda. I had been buying some various sized o-rings from eBay sellers in China for use on Honda Dream carb flanges, so one of those was popped into the groove when the carburetor was installed.

The fuel tank was purged of the old gas and refreshed with some of 7-11’s finest 91 octane brew. With a new piece of OEM Honda fuel line, the carb was again reconnected to the fuel supply. The original battery was a small electronics store item, which was marked “Removed in 2003.” The battery wire ends were changed to the small push-on connectors, but I had ordered an old-school lead-acid battery which is big enough to support an electric starter, but these bikes never had that option. I snipped off the wire ends and found some ring terminals that would fit the 6mm battery bolts normally used with these batteries. With the fully-charged 6v battery installed, the switch was turned to ON and the bike lit up with all functions working as designed. Yeah!

With fresh gas on the tank, A few good kicks and the bike started up, sounding sweet and healthy with no smoke out the muffler (thankfully no muffler rot for some reason). The original tires were rock-hard, so a brief and gentle spin around the block was enough to confirm that the transmission and clutch seemed to be working properly.

2 weeks later…

The little CL125A was treated to a new set of tires and tubes, plus fresh carburetor parts that amounted to $60 worth of purchases. I re-learned a valuable lesson about setting up the carburetor diaphragm system when I installed the central plunger in upside down. There is a long and short end to the spring-loaded plunger and when it is installed with the long end up, the throttle goes to wide open revs as soon as the engine lights off. This is VERY disconcerting, to say the least. After a few rechecks, I finally looked at the illustrations of the carburetor and saw that the long end of the plunger goes DOWN. Properly installed, the carburetor assumes normal function once again.

The exhaust system is all stock and the drain hole at the back was still open and there seemed to be plenty of material underneath the muffler, instead of finding the usual rot that happens with time and operation. When the muffler was removed, a surprising hole was discovered on the back side of the muffler relief where it curls around the rear shock. Apparently the rear mounts were bent or not installed correctly and the shock wore a whole in the muffler body. A trip to my friend Rob North’s shop resulted in a mended muffler which then needed a hard-to-find muffler packing for the slip-in left exhaust header pipe. After tracking down a small batch of them, the muffler was finally installed and should function as designed.

NOS old school cables were ordered and installed. The clutch cable installation requires removal of the rear sprocket cover which revealed that the front sprocket was a 16t instead of the stock 15t size. Test rides showed that the bike was unable to sustain a good speed up the long hill to the house from the local PO. It would rev high in 2^nd to about 40 mph, then just bog down in 3^rd gear under full power. A 15t sprocket was ordered and installed when the cable was changed. The clutch adjuster was found to be extremely tight in the side cover, requiring cover removal and a good bit of time to extract the adjuster and then refit it in the hole so it turned more easily. All these little tasks wind up taking up quite a bit of time to correct during a revival process…

Next improvements are a new right side fork ear, fork seals and a new headlight rim.

When Super Hawks go rogue…

Most people think of the standard CB72-77 Super Hawk in conventional terms; a flat-bar machine with a dual seat, a 180 degree-firing crankshaft engine design, dual carburetors, a 4-speed transmission, stopped by 200mm DLS brakes and rolling on 18” wheels/tires. Honda made something over 137,000 Super Hawks for worldwide distribution from 1961 to 1967, in various guises; some of which have never been seen or are seldom seen, even to this day.  Even in the beginning of the 1961 production machines, there were exceptions to the conventional CB72-77 models.

Engines                                                                Frames                                                 Features

‘61 Type

CB72E - 110001 - 113443                CB72 - 10001 – 13443                      The first 366 units were prototypes

CB72E - 150001 - 151657                CB72 - 50001 – 51657                      Type 2

CB77E - 110001 - 111249                CB77 - 10001 – 11249                      US models

CB77E - 150001 - 150480                CB77 - 50001 – 50480                      Type 2

CP77E - 110001 - 110080                                 CP77 - 10001 – 10080                       Non-Police

‘62 Type

CB72E - 210001 - 211880                CB72 - 21001 – 21881                     

CB72E - 260001 - 263469                CB72 - 60001 – 63444                      Type 2

CB77E - 210001 - 210900                CB77 - 20001 – 20902                      US models

CB77E - 260001 - 260395                CB77 - 26001 – 60395                      Type 2 ? I own #474!

CP77E - 210001 - 210228                                 CP77 - 20001 – 20228                       Non-Police           

‘63 Type

CB72E - 310001 - 315446                CB72 - 310001 - 315446

CB77E - 310001 - 319222                CB77 - 310001 - 319222

CB77E - 340001 - 340015                CB77 - 340001 – 340015                  Type 2

CP77E - 310001 - 311094                                 CP77 - 310001 – 311094                  Non-Police

CP77E - 340001 - 342015                                 CP77 - 340001 – 342015                  Police Type 2, rotary gearbox

CP77E - 3100001- 3100100             CP77 - 3100001 - 3100100

‘64 Type (1)  Six digit starting with 1

CB72E - 100001 - 104165                CB72 - 100001 – 104165                 

CB77E - 100001 - 109755                CB77 - 100001 - 109755

CP77E - 1100001- 1100803             CP77 - 1100001 – 1100803              Non-Police

‘64 Type (2) 6 digit starting with 4

CB72E - 400001- 402754                                 CB72 - 400001 - 402707

CB77E - 400001- 403838                                 CB77 - 400001 - 403841

CP77E - 4000001 - 4001260            CP77 - 4000001 - 4001103

CP77E - 4900001 -4901223             CP77 - 4900001 – 4900641              Police Type 2, rotary gearbox

’65-67 “The machines which were discontinued the year of manufacture are as follows:”

CB72E -1000001 - 1006342            CB72-1000001 – 1010918                               Numbers don’t match up!

CB77E -1000001 - 1056494            CB77-1000001 - 1056432

CP77E -1000001 - 1002015             CP77 -1000001 – 1001966               Non-Police                                                                CP77E -1900001 - 1901540                CP77 -1900001 – 1901535               Police Type 2 Rotary gearbox

Totals, based upon this chart, (which has errors!) = 137,240! That’s a LOT of Super Hawks! But that’s not all!

What is not shown clearly on the Honda production chart above are these unusual versions:

CM72 models, primarily 1961 and some early 1962 editions. These bikes were a cross between a Dream and a Super Hawk; solo seat, luggage rack on the back, single-carburetor, 360 crankshaft, rotary gearbox, single Scrambler-type speedometer, sidestand, winkers, early tail light.

CBM72 models, standard 250 Super Hawks, which have Type 2 engines installed. I have owned at least one of them and have seen others.

The Type 2-powered bikes used a 360 crankshaft, left cam with different master spline location, Dream points/point camshaft, special mounted twin-lead coil/condenser and a TYPE 2 labeled point cover. The cam timing was normal CB series lift/duration and carburetion was normal to any other CB. While there were Type 2 engines installed in 250cc Scramblers, no Type 2 engines were used in 305cc form. However, the 305cc CYP77 Police models did have Type 2 crankshafts.

In 2002, I was able to rebuild a genuine CYP77 Police bike, but the original engine was missing. I did come up with some engine cases that were stamped CP77, but the second digit (9) was not present, because they were for a non-Police application. I purchased a new Dream crankshaft for the 360 firing order. I ground off one of the splines on the left camshaft, which allowed the correct 360 degree firing. Fortunately, a genuine Type 2 ignition coil and condenser was available from a source in Canada to complete the installation, as close to original as possible. Because the Police bike rotary gearbox components were not available to me, I used a conventional CB77 gearbox with X’d gears in the transmission. The bike turned out well, with good low-end power and strong mid-range, too.

The oft-mentioned 1962 Type 2 CB77, currently in the stable of bikes, was built in the early 1990s and was treated to the then-available CYB racing parts, including the alloy rear fender, shift lever/rod, fork crown, clip-on handlebars, special fork cover clamps, hydraulic steering damper, steering stop and the factory racing seat.

I can’t recall exactly how I came upon the chassis in the beginning, as it was definitely not a US spec model. Following the domestic Japanese frame numbering system used in the first few years, the year is stamped in the middle of the frame number, so the frame is CB77-62-260474, where the 6 denotes a Type 2 engine that year. Honda used 4, 5, 6 and 9 as designators for Type 2 engine models through the years, although the 9 also designates a CYP77 Police model.

Honda stamped CP77 on both Police and non-Police versions, calling the Police model a CYP77 in the parts books (282 product code). The regular CP77 (281 product code) was a standard Super Hawk equipped with high handlebars, winkers, side stand, solid footpegs and the early style tail lights only seen in the US on 1961 CB77s. CP77s used that same tail light through 1965-66, while the rest of the export models used the more conventional CB72 generic tail light assembly from 1963-66. 1967 model bikes received the oval tail light treatment, along with some chrome fenders on the last 200 machines built.

Some sources report that many of the CYP77 Police models were used by the Army in Malaysia or Indonesia, back in the 1960s. There is ONE bike in Norway and perhaps TWO in the UK. Very few have ever come up for sale or even in photos. My CYP77 came out of Canada, where they did bring in a limited quantity of bikes and stocked parts for them briefly. There are several Facebook pages for vintage model Hondas, including a couple for the 250-305 Super Hawks. Recently a CYP77 was revealed in as-found condition down in SE Asia, but that is a rare occurrence these days.

Super Hawks are celebrating their 56^th year anniversary of their release. While really good originals or even carefully restored bikes are becoming more scarce, you can see that there were many, many bikes produced and a good 68,000+ were sold right here in the US.  I got mine… go find yours!

1962 CB77 Type 2 cafe' racer version with CYB72 racing parts installed.

                                                 
                                         Honda CM72 image from a show in Thailand

Someone didn’t read the book… How wrong can you be?

Well-intentioned efforts to rescue at least one CB77, from a stash of 5 bikes which sat outdoors, near the ocean, for some 20 years can involve a lot of twists and turns in the adventure.

My friend Steve, whom I steered towards the horde of Super Hawks (and a couple of other strays) has been sifting through several engines in hopes of finding one that was worthy of repair and overhauling. The first engine removed had cylinders full of corrosion, rust and other contaminants. Unfortunately, that engine was the match to the best of the CB77 frames in the pack. One of the bikes is a PI issued CB72 250 Hawk, so while some of the lower end parts are interchangeable, the top end components and crankshaft are all of different specifications.

On the second engine pull, Steve was shocked to discover cylinders with brand new pistons and rings, nestled in nice honed bores, all ready to go to work. The valves in the head were all new replacements and it looked like the best path to success, once the engine was completely disassembled for a thorough cleaning and inspection of the internals. With the top end already dismantled, it was time to turn attention to the lower end in hopes that the crankshaft, rods and transmission components were all in similar condition.

At first glance, it was noted that the infamous crankshaft locating pin on the rotor end of the crank was pushed up into the engine case and the displaced chunk of aluminum was subsequently glued back down in place. Unfortunately, the patch seemed to be displaced once again, so it seemed like more troubles could be lurking below. And so they were…

The kickstarter cover was still mostly in place, however it was broken in half and just shards of aluminum remained attached to the lower edge of the bottom case. The case and stator were removed to allow access to the rotor for removal. Normally, the central bolt is a special one with a 14mm head. This bolt had a 7/16” sized bolt head holding the rotor onto the end of the crankshaft end. Once the rotor was dislodged from the crankshaft snout, the back side of the starter clutch looked pretty much destroyed with the wrong screws installed and rollers and the back cover plate damaged severely. 

There won’t be any reusing of those parts in the future.

I use a long #3 Phillips impact bit to loosen the clutch cover screws, hitting the bit with a hammer first, then using an impact drive to twist them loose enough for removal. That process worked well and the clutch cover came loose after some use of a plastic mallet and even some screwdrivers to pry along the edges. Once the cover was removed, the outer oil filter boss was seen as dimpled in a few locations where someone had tried to pound it onto the clutch cover without regard to the position of the oil filter shaft locating pin. The thrust washer was nowhere to be found and the order of installation of the crankshaft washers and nut were somewhat incorrect. I happened to notice that one of the primary chain rollers was split down the sides! The clutch assembly looked new, but the plates were all stuck together from sitting for so long.

With the forward sprocket, primary chain and clutch outer basket removed as a unit, the shift shaft slid out of its position easily. Standing back to look at the whole side of the engine, it was shocking to find that the primary chain tensioner and bracket hardware were all missing! Not only that, there was a strange-looking bolt in place of the stopper bolt for the kickstarter shaft end. When the bolt was removed, it was found to be a self-tapping oil drain plug, not a transmission stopper bolt! It was way too short to even begin to contact the end of the kickstarter shaft end as designed. All it did was to plug a hole.

The bolts for the shift selector parts were not very tight, but nothing had dislodged after the reassembly. From the looks of it, the engine was never run at all after the aborted attempt to reassemble the engine correctly. Thank goodness for that miracle!

With the whole clutch side of the engine cleaned off of components, it was time to split the cases to see what kind of shape the transmission was in and how far off the crankshaft bearing pin hole in the main bearing was located.

The cases had been sealed with Permatex gasket sealer; fortunately the non-hardening type. With the bottom case pulled up and away a look at the transmission gears and shifting seemed to be somewhat normal with some minimal gear dog overlap on the countershaft gears. When the countershaft was removed to inspect the kickstarter pawl function, the end of the shaft was damaged, the pawl was loose inside the engine case and the end bushing had a huge gouge along the edge of the bushing face. My best guess, forensically, was that the kickstarter pawl was installed backwards, which causes them to fly out of the end of the kickstarter shaft end, where the pawl interfaces with the inside of the transmission’s low gear. The stepped, 14mm bushing was in decent shape, probably due to being replaced during the attempted repairs.

The main shaft and gears all seemed to be in serviceable condition and the assembly set aside for cleaning. With the transmission shafts and shift forks/drum removed, the last item on the agenda was the crankshaft. I already knew there was a problem with the rotor end of the crankshaft, however I was appalled to discover that all of the main bearing oil holes were in disarray and completely out of position. The rotor end main bearing was a ball-bearing instead of the normal roller type. This kind of substitution is generally used when the main bearing and crankshaft bearing surface on that end has been damaged.

As the crankshaft was lifted out of the engine case, I discovered that all of the other three crankshaft main bearing locating pins were missing! Without the locating pins to index the bearings, the mains can only get a little splash feed to lubricate the needle/roller bearings, instead of the normal flow of oil that trickles down from the upper end and is funneled into the main bearing feed holes. How can it get worse than this?

Well, it did, in that the oil pump drain bolt was discovered to be another self-tapping automotive drain bolt and one of the pump attachment bolts into the bottom case was an SAE bolt, instead of a 6mm metric bolt.

With the lower end all torn down and inspected, the cylinder head was brought to the bench for disassembly. There were signs of a lot of water going down the intake ports, but luckily the intake valves were both closed when the engine was installed back into the chassis. All of the valves had nice fresh margins, so were obviously new when installed. The camshaft lobes had scoring and discoloration consistent with a lack of lubrication. The rocker arms, however, were the early side-feed versions and really had no matching wear to that of the camshaft lobes. That’s very unusual! The camsprocket was in good shape, but the advancer shaft was stuck in place initially. The points cover had been left off the bike so the end of the point cam was heavily rusted and frozen in place. Things loosed up after disassembly and the point shaft might be reusable with some cleaning and polishing of the point cam lobe.

The pistons were mostly all shiny, however the top ring of one side was a little rusted into the piston groove, but finally loosened up with an application of penetrating oil and some gentle prying with a small, scribe-tipped tool. The cylinder bores still had a nice cross-hatch finish and should be perfect for refitting the pistons and breaking the engine in, as was originally intentioned.

Steve is faced with either having me rebuild this engine, which has non-matching engine numbers for the frame he will use OR he will bring the matching engine down for an attempt to penetrate the corrosion in the cylinders sufficiently to allow the cylinders and pistons to be removed so the 

crankcase can be reused for the engine rebuild. I hope that no one has done the same thing to the other engine as what was done to this one by someone who just couldn’t read the book!

Kickstarter pawl found in the bottom of the engine after egress from the shaft end.

Severely worn end bushing which didn't help the kickstarter pawl stay put.

Crankshaft main bearing oil holes all out of alignment

Ball bearing installed on the crankshaft to repair damaged bearing surfaces.

Ah, these holes are not supposed to be seen like this.

Locating pins all missing from the main bearing locations.

Rotor end of crankshaft had main bearing locating pin pushed into the engine case.

Wheels, rims, spokes and all those funny angles…

As long as I am embarrassing myself this month, I have to confess to another miscue that was based upon observed problems in the past, coupled with mis-identification of parts.

That Scarlet Red 1962 CB77 had been carrying one of the DOT stamped rims up front since it was built back in the 1990s. Aficionados of restored vintage Hondas really don’t want to use the replacement rims which Honda was required to produce and sell since the early 1980s. There is nothing subtle about the big DOT required rim labels, in this case “J 1.60x18 7 84 DOT” vs. the little tidy “DID” logo in between the spoke holes, plus 1.60x18 lightly stamped nearby on the flat edge in this case.

I had already purchased CB77 spoke kits from Marty Mattern at 4into1.com as the spokes on the bike were pretty corroded, having sat not far from the ocean for 25 years. The chrome on the rim was remarkably good, but seeing those giant letters was distracting. New tires had just arrived and the plan was to re-spoke the wheel and install new rubber for safe driving duties. While digging around beneath my work table, I discovered this apparently unused 1.60x18 DID rim which I had no recollection of acquiring whatsoever. It seemed like divine intervention to have a perfectly good rim show up like that to replace the ugly DOD version so after a bit of cleaning up, I was ready to take on the rebuilding task.

Once the tire was pried off the old rim, the corroded spokes came out fairly easily and the rim/spoke swap began in earnest. Unfortunately, when the spokes were sorted out, there were 19 inner spokes and 17 outers packed into the kit! Not a good start already…

The spokes all installed without difficulty, however once the nipples were snugged down evenly the spoke angles were all a bit “off” with gentle curves coming out of the nipples and across the expanse to the hub. That’s not right, obviously! After taking a couple of photos of the misguided spokes, I jumped to the conclusion that the spoke kit was one of those errant versions from Thailand that I had seen in the past on various Dreams and some Super Hawks. Some of those rim/spoke kits had severely kinked spokes once they were tightened up and I figured that must have been what happened here… cheap spoke kits!

I fired off photos to Marty to show the results of the spoke job and wanted to know if he had other complaints of them in the past. According to Marty, they have sold over 100 kits without complaints. Well, how could that be? Obviously, I was fairly certain that I was dealing with OEM Honda parts in the rim and hubs, which had been aligned perfectly before I changed the spokes. The rim looked correct, and was the same size as those of the CB72-77s which never changed through the years. When you see a DID rim with 1.60x18 stamped on it and it has a 36 hole pattern, it MUST be for a Super Hawk, right?

Well, after exhaustive comparisons between the OEM spokes and nipples and the a/m kit parts, only a few minute differences were apparent, but perhaps they were sufficient to cause this problem. None of it really made sense as I tried to noodle it out in my mind. All that was left to do was to pull the wheel off and apart, once again and compare the rims carefully, side-by-side.

Using a digital micrometer, I measured out the distances between the first two spoke holes on each rim, just beyond the valve stem hole. Well, they were just slightly different in that measurement. So I expanded the measurements out as far as the caliper would allow, which was about four holes apart and the figures came out substantially different, to the tune of a millimeter and a half as I recall.

I stripped the rest of the spokes from the hub and rim and switched back to the DOT rim for reassembly. Lo and behold, the spokes straightened out just fine without any kinks or bends coming out of the nipples or across the expanse between the nipple and the hub! So, apparently, the “CB77” front DID rim was, in fact, a rim for a Honda CB160 instead! The CB160 has a 180mm brake vs. the 200mm brakes on the CB72-77s, but the flange holes must be fairly close to the same in allowing the 160 rim to spoke up to the CB77 hub with just a little bit of deflection in the spoke angles. Ah, another lesson learned and to be shared with those who might/may have encountered a similar situation. The similarity of the two rims was certainly sufficient enough to fool MrHonda, so don’t let it happen to you, too!

After apologies to Marty and his supplier with emails entitled “Mea Culpa,” I think I learned my lesson on this one, for sure. However, there ARE rim/spoke kits out there from SE Asian sellers, which were made to either Benly or CB160 specs but being offered as replacements for full-sized Dreams and Super Hawks. So “buyer beware” on those offerings and check with others, on the various forums, who have encountered problems and successes with these wheel kits being offered from across the sea.

Thanks to Marty Mattern at www.4into1.com for his patience and understanding, as I muddled through this problem which had nothing to do with the quality of his products. While I was in the midst of discovering the actual cause of the problem, a phrase from that popular song by the group Level 42, called “Something About You” goes:And it's not so wrong; we're only human after all,” kept running through my mind. 

Yes, even MrHonda is human after all.

There ARE differences between the two spokes.

                                                  Bent spokes on the first attempt.

“

                                            Success in the end, returning to the original DOT rim.

How many experts does it take to make a CB77 run right?

It has been a push-pull experience with the 1962 CB77 Type 2 café racer bike during these past few weeks. After the initial excitement of “re-owning” the bike again (after it was away for 25 years) the reality of what had been built and what it needed to run properly again has caused unending headaches.

First, the fuel system was contaminated with 25 year-old gasoline residue, which attacked the old KREEM tank liner. After flushing out the old gasoline deposits (I thought), fresh fuel was added as the bike was brought back alive with a new battery and carb cleanout. Apparently the Kreem leftovers contaminated the new gasoline to the extent that it created a gummy substance that caused the carb slides to gum up and hang partially open. After cleaning the carbs several times, the tank was finally treated to a full strip cleanout and coating with POR15 sealer. Of course the petcock and carbs all needed to be cleaned again to rid themselves of the gooey gum deposits. What also happened was that the old contaminated fuel that did go through the system coated the insides of the intake ports with slime, which kept getting spit back onto the back sides of the carb slides, even after the fuel system was cleansed and sealed.

The motor has been out four times now for:

1. Cam sprocket replacement with a Dream unit; falsely thought to be the cause of ignition system inaccuracies. The point cam was the actual culprit.

2. Removed for a bottom end teardown, initially to correct shifting issues and noises. One offset cotter was cracked in half and I discovered that the main bearing locating pin had been pushed through the engine case, so that needed repairing. While it was apart, the rest of the top end was taken apart so that an endless camchain could be installed and an oversized piston pin was put in the left side rod. After the engine was reinstalled and run, the clutch pushrod seal dislodged and blew out all of the engine oil during a 15-minute test run. A new seal was installed with Lock-Tite.

3. Engine out again to replace the “repaired” CA77 Dream camsprocket, which was suffering from too much spark advance, too early, causing engine idling issues. When engine was reassembled, the wrong set of timing marks were used as reference points for cam timing, resulting in ZERO compression, discovered when the bike starting attempts failed. 

4. Instead of pulling the entire engine out of the chassis, the bottom rear bolts were left loose and the engine tipped downwards towards the front fender. This left sufficient clearance to remove the cams and rotate the camsprocket 180 degrees for proper cam timing. Compression readings returned to 180 psi on both sides. Bike started up okay, but ignition timing continues to advance out somewhat when engine is operated and returns to idle.

Initial start up was rocky as it wasn’t running on the left side, at idle. After cleaning the idle jet, the start- up improved, but part throttle was dodgy until about half throttle. Closer inspection showed that the carb slides had gotten out of synch and then the ends of the needle tips were not hanging out of the bottom of the carburetors equally. Slides were removed and the right side needle had no numbers on it; apparently an early Keyster kit needle. Replacement of the needle with an OEM version and careful carb slide synch made things much better, but the erratic hot idle conditions remain.

After careful reshaping, the point cam timing ramps are about exactly the same, so that earlier erratic timing problem has been solved. The problem with the whole system is that the return springs for the weights don’t fully pull the weights back into the resting position. There is ALWAYS some slack/slop in the mechanism. The springs are not terrifically strong, so it is easy to twist the point cam and feel the looseness in the parts. Worn point cam shaft shoulders, which ride inside the right side camshaft, can induce timing errors as the point cam wobbles around during each revolution. This is especially noticeable with normal Type 1 engines where one point cam lobe opens two different sets of points that are located across from each other.

Additionally, what I have noticed is that the point cam seal lip grip, enhanced by the coil spring on the back side, grabs the point cam with enough tension to prevent it from returning to resting position at idle. The seal friction, plus the inherent play in the camsprocket components, prevents accurate ignition timing at all engine speeds. This CB77 Type 2 engine can be statically timed at the F mark on both cylinder rotations, but when the engine is started up, the spark timing jumps out five to ten degrees immediately and quickly ramps up to the full 45 degrees, well before the stated 3300 rpms, in most cases.

Controlling the idle speed/quality requires the cooperation of a stable idle spark timing setting, balanced carburetor slide openings, idle mixture screws that are functioning properly, the correct float level setting, idle jets that are right for the application, even compression readings, no air leaks at the carburetor flanges and insulator o-rings and minimized oil consumption. If any of these functions are compromised, the entire engine function suffers, especially at idle. Hampering effective combustion is the fact that the intake ports are not directly mirror images of each other. One intake charge is aimed directly at the spark plug for one cylinder, but the opposite side fuel vapor flow points away from the spark plug tip.

The only way to totally control the spark advance on these engines is either the crank-mounted system from Germany ($500) or an electronic spark advance system using the point cam as an initial trigger. The problem there is that you need to lock up the spark advance system permanently, so the electronics can do their thing correctly. Dealing with a nearly 60 year-old design presents more and more problems as the parts age and wear over time.

The Sin of Omission… 1964 CA77 clutch mystery-solved!

My friend, Javier, has a bright red CA77 Dream which he’s used sparingly for the past 6+ years. He called the other day to ask me to help him solve a shifting problem that he had suddenly encountered. Despite monthly rides to keep the bike in operating condition, suddenly the clutch wouldn’t disengage when he tried to ride it last week.

All the symptoms sounded like a “stuck clutch” syndrome, which often happens when the bikes are laid up for many years. It didn’t make much sense that the clutch would suddenly act up like that after regular use, so the only thing to do was to have him bring it over for a look. After checking the clutch cable and clutch adjuster for proper settings, the bike continued to lurch into gear and die when any attempt to drive it began. I suggested that he ride it down the driveway in neutral, pull in the clutch and drop it into gear; then continue to ride the bike up and down the street in gear with the clutch lever pulled in to see if it would break loose. He had no luck doing that, so was obviously time for a clutch inspection!

The bike is mostly stock except for front crash bars, rear grab rail and some re-purposed HD mufflers installed on the stock header pipes. The oil was drained and work commenced on disassembling the left side of the bike; exhaust pipe/muffler, footpeg, shift lever, oil filter cover and all the clutch cover case screws (Socket head screws on this machine). The oil came out a little dirty after circulating for the past 5 years, but there were no signs of any large particles in the drain pan and the engine’s left side components were all relatively clean showing that someone had done an overhaul on it during the restoration process.

Once the cover is off, it only takes removal of four bolts to remove the clutch pack from the engine. The clutch pack combo came out like a brick and the remaining clutch plate set, held in with the retainer wires, was stuck together as well. It is hard to imagine that the bike could have been recently driven with a clutch that looked like this. The clutch inner hub was removed and the outer wire carefully taken out of the hub to release the inner clutch plate set. All the clutch plates were pried apart and the steel plates all scrubbed up on a wire wheel. The fiber plates were scrubbed on a Scotchbrite pad, just enough to rough them up a bit. The surfaces were all glazed to some extent, but not from excess slipping or abuse.

With everything cleaned up, the clutch pack was reassembled onto the engine. I fully expected to have a fully functioning clutch now, but after bolting down the outer clutch pressure plate with the four bolts, washers and springs, it was apparent that something was missing! The outer spring-loaded plunger, which is called a “metal oil guide,” was nowhere to be found! It hadn’t fallen out into the drain pan because it was never there in the first place! Whoever had built the engine failed to install the part, which is crucial to supplying oil to the clutch and transmission shafts. The metal oil guide is the bridge between the oil feed hole in the clutch cover and the center of the clutch pressure plate to supply the clutch and transmission with fresh oil. Not only does the oil fail to be delivered to the transmission shafts, the oil which would normally go to the oil filter on the way to the crankshaft bearings is dumped back into the clutch cover, through the existing gap between the cover and the outside of the clutch pressure plate.

I recalled hearing the engine run, years before, there were unusually loud rumbling noises that seemed to sound like bad crankshaft bearings to me. I heard it again when the bike was being run during the attempt to break the clutch loose, prior to teardown. Javier hurriedly fired the bike up and ran it around the block, then shut it down to be loaded back into his truck before I could get a good listen to the engine after the repairs, but I suspect that the crankshaft is going to be a lot happier with a full flow of oil to the bearings from now on.