Back in the saddle with 250-305s again…

After running through a handful of interesting JDM bike and thinning out my little herd, the inevitable return of 250-305s began in the past few weeks.

Chapter 1:  CB77 for sale... not bought

A friend alerted me to a CL posting for a 1965-ish CB77 for sale at $1100 asking price. Photos showed oversized tires on both ends, missing fenders, an a/m seat and the wrong mufflers, just to start with. The bike was 50 miles away, but I already had some business in the area so it wasn’t too much trouble to cruise over and have a look. The seller was a nice mid-aged man who had put together a café CB550 project and had gotten the CB77 from a friend who first wanted to make a custom bike out of it, then decided to sell it as-is. Photos did it too much credit as the chassis had been modified around the forward seat mounts and the black chassis had a red front end attached. The ignition switch and the fork lock numbers didn’t match, so I assumed that the front end was replaced from another bike.

It wasn’t running due to dead battery, stuck carb slides and the usual faults found on a long-abandoned project bike. It needed a chain guard and a new wiring harness, which I happened to have left in my parts stock, but the more I considered it the more I kept remembering all the CB77s that I spent endless hours on to get running, then wind up selling them for what I had spent on parts and services. Somehow I found the strength to say NO, even to a reduced price of $800. I was proud of myself for walking away from another “project” that would have no financial reward at the end, whatsoever.

Chapter 2: Domestic CL72 engine rebuild

A few months ago, my longtime friend J. Braun inquired as to whether I would “rebuild my CL72 engine,” which I assumed would be just doing the engine, brought down in a box. After a long, long haul from UT, he arrived with a whole CL72 Scrambler in the back of the truck! After some discussion, I offered to remove the engine while he went back to his overnight lodgings to check in, then he would come back to pick up the chassis and haul it back home the next day. I had the engine out in the first hour and the top end removed from the “stuck” engine by the end of the 2^nd hour. We went to a nice Italian restaurant for dinner, in celebration of my 70^th birthday, then he brought me back home and we loaded the chassis into the truck.

The following day, I spent another 2 more hours carefully disassembling the very dirty and corroded engine which happened to be a domestic Type 2 (360 firing crankshaft) model. Fortunately, the crankshaft seemed to be in great shape, so the rest of the work will be extensive cleaning, prepping a spare set of cylinders for use and rounding up the required expendables like seals, gaskets, primary chain, camchain, bushings and kickstarter pawl bits.

The pistons removed were already .25 oversized, but were stuck in their bores due to water going down one intake side, through the carburetor and into the cylinder. The bike was last ridden in the early 1990s and then left in a corner of a shop for the next 25+ years. J remembers riding the bike, but seemed unaware that it was a Type 2 powerplant. The bike did have a kph speedometer and the remnants of the factory turn signal switch on the right side handlebar end. Most of the winker system parts were long-gone, but the original heel-toe shifter remained. These bikes came with non-folding driver footpegs and among the parts were 2 sets of NOS 273-000 footpegs to match the application.

It seems to take a couple of weeks to get all the parts cleaned properly and replacements lined up for the reassembly process. Overall, the engine components are all usable, without any of usual broken fins and similar damage often found in a bike like this which was being used as designed… as an on-road and off road machine.

As an unexpected bonus, J brought down 6 boxes of mostly NOS Honda parts for Scramblers and Super Hawks. There were a couple dozen of those little standup envelopes containing many small parts needed to rebuild these engines. There was spare ignition switches, unused and used, plus CL72 air filters, many sets of levers, NOS CB77 black cables and a variety of interesting bits. A good bit of it will go into the engine rebuild, with the rest offered on FB forums or eBay if all else fails.

Chapter 3: Return of the 1962 CB77 #25

It was old-home week as a revived 1962 CB77 with frame number 25 returned here for some troubleshooting and maintenance updates. I had received the bike as a rusty, corroded hulk with seized engine and lots of damage from moisture due to its long-term storage near the ocean, inside a shipping container. I only had 30 days to complete the revival, as I was scheduled for knee replacement surgery on day 31. I had written the whole story for my former internet host, the “Examiner.com” site which suddenly went dark a few years back. Fortunately, I had all the original stories saved on my computer and made a backup copy from the website before they closed.

The repairs were massive, despite the bike only having 2300 original miles showing on the speedometer. Even the tires and tubes were original OHTSU branded from the factory and while in terrible condition it was worthy of a quick rebuild and documentation of what exactly was and wasn’t changed on the first day of production for the 1962 models.

The bike was sold to a LA enthusiast who is active in the LA region of vintage Japanese motorcycles. With little break-in time, he rode the bike all the way out to their annual Death Valley desert run, which was some 350 miles away. The bike survived the trip and actually made another run the following year. With changing priorities, the owner decided to put the bike up for sale, but the Super Hawk began a series of misbehaviors, including dropping the left side cylinder intermittently. To help regain reliable ignition functions, a new electronic ignition system from Charlie’s Place was purchased and installed. The way the system is designed, there are some limitations as to the positioning of the control module which prevented installation of the point cover, if moved much beyond the center of the adjustment slot. The trigger wheel, which attaches to the end of the points cam can be installed in a 90 degree spread of options, so for successful installation the trigger wheel must be set, tested for timing function and then adjusted again when the timing was excessively advanced or retarded.

The instructions were a bit vague and there was a lot of trial and error until the full function was understood and the final adjustments locked in place. With the ignition setup correctly, the bike fired up immediately. I had checked the compression and idle jets for being clear, prior to finalizing the ignition timing. The bike warmed up quickly and I decided to take it for one last test run before it disappeared from my life forever. I barely got a ½ mile away and noticed that the clutch was slipping under anything more than half throttle. Coming back up the test hill nearby, the clutch was slipping and sliding all the way up, unless the throttle was modulated carefully. Then, there were the oil leak issues, which had been mentioned previously. A quick look showed oil coming out of the outer oil filter cover, down the tachometer cable and the shift shaft seal. All the next work was to be on the left side of the engine, so I had hopes that most of the leaks could be solved with replacements of o-rings and seals.

So, the unplanned services now included a clutch inspection, which requires draining the oil (good thing as it was needed anyway) and removal of the left side clutch cover to access the internals. Once the cover was removed, everything inside still looked pretty clean and shiny inside. The clutch was the original 6 plate version, to which I added some 323 coded (CB500) clutch springs which normally prevent clutch slippage. All the plates seemed pretty good still, so I bumped the springs up to some 374 code parts, which are for the CB550 and are a big longer than the CB500 versions. Before the clutch cover was reinstalled we checked for clutch lever pull effort, which seemed to still be reasonable to both of us.

I replaced the outer oil filter covers two o-rings, installed a new shift shaft seal and rechecked the cover for any high spots which can cause common gasket leaks in these engines. With the engine buttoned up and new Honda GN4 oil added, the bike was tested once again and this time the clutch function was normal, but the oil filter cover still had a bit of a weep even with new o-rings! I suggested that he make a thin paper gasket and seal the cover that way, which seems to be the only other way to contain the leak. It is an uncommon problem in my experience, however this early engine had the “small hole” cover and filter cover, which was revised later with a larger access hole and an extra o-ring in the clutch cover case to help seal it more effectively.

Starting at his 9am arrival time, we worked continuously until well past 1pm on Memorial Day. All the work paid off in getting the bike up and running, plus curing most of the unmentioned issues with the clutch and oil sealing problems. The bike is a solid example of Honda’s earliest CB77 efforts and an interesting transition bike from the 1961 year to some of the changes in the 1962 models. Looking at parts books, there were more changes to come as the 1962s continued in production, but this was a true example of what happened as Honda ramped up into the second year of Super Hawk sales.

It is bittersweet to revisit a bike that you built a few years before and then had to hand off to another CB77 enthusiast. Hopefully, the next owner will be inclined to spend some money and time on re-chroming and polishing the corroded bits that remain and give it a place of honor in their garage and out on the roads!

Bill Silver

aka MrHonda

Lucky to be here for #70

Starting my 7^th decade on Thursday May 24, I have to stop and be grateful for all the blessings in my life of family and many motorcycle friends around the world.

I have had three different motorcycle crashes that could have taken me out for good, but somehow I survived them all and still enjoy riding my bikes regularly. Current stable includes the 1988 CBR250R, a 2013 PCX150 and a 2013 CB1100. There is a possibility of another CB77 coming my way next week, but that’s not for sure.

I lost track of all the bikes and cars that I have owned/sold in the past 50 years, but I think it has ranged upwards towards 400, starting with my 1967 CL90 Scrambler, the first bike I ever owned. Since then the bike list ranged from a 1954 F Cub to a few CBXs with lots of 250-305s in the mix of all types. In the last year I have had a handful of JDM bikes that I never imagined owning and riding, including a 1997 Dream 50 street bike, 1968 domestic CB350 (with CB77 style fuel tank) and a pair of CBR250R bikes with 18k redlines. It is now just possible to sample more JDM models here in the US due to the 25 year old rule kicking in favoring some of the unusual Japanese bikes and cars which we could never experience until now.

I missed the opportunity to have a long-term "life partner" who shared my enthusiasm for motorcycles, but at least they tolerated them while we were together. I am fortunate to be in a relationship now with a woman who grew up riding Honda CB160s and CB175s (without a helmet). She "gets" the attraction of motorcycles and appreciates that I am a key figure in the world of vintage Honda motorcycles. That is a rare quality in women in my experience and I am grateful for that now.

It is gratifying to see more women become involved in rides and motorcycles in the past few years. Motorcycle ownership and riding is waning somewhat according to the latest news reports. Current generations of eligible riders have delayed even getting a driver’s license at all as other transportation options have become available, like ride-sharing and an emphasis on bicycles. 

The face of motorcycling, as a whole, is changing with the latest technologies in electric cars and motorcycles. It is hard to imagine riding motorcycles which basically are completely silent apart from the gear whirring of the electric powertrains. Future generations will miss out on the roar of the Honda CBX six’s wailing exhaust systems or the mechanical commotion of a small 250cc four cylinder bike with a 18-19k redline as it peaks past what seems to be impossible revolutions for an internal combustion engine.

As we look to the future, however, the continued burning of fossil fuels appears to still have consequences to the global environment. Banning diesel and gas powered vehicles may well help stem the tide of carbon dioxide that filters upwards into our precious atmosphere which has caused the conditions of global warming or at least been a contributor to it for the past 100 years. How different the world will be in another 25 or 50 years, assuming that we are able to reverse some of the climate changes in some way or other.

For people of my generation, we have watched an amazing transformation of automotive and motorcycle technology starting with ancient and ineffective combustion engines that would ping and detonate with an 8.0:1 compression because the fuels were not sufficient to support anything higher than that. Today we have street bikes with 150-200+ horsepower, still running on premium alcohol injected fuels, despite compression ratios in the 12 to 13:1 range.

My first “real car” was a 1956 Ford 4-door with a 272 cu in engine, three speed stick shift on the column and a 2bbl carburetor. I think that it usually got about 14 mpg perhaps, but gasoline was $.25 a gallon back then, so fuel costs were not a particularly big concern. Disc brakes were unheard of back then, apart from being on exotic racing cars or airplanes. Four troublesome drum brakes were the only option back in the 1950s; and you had to keep an eye on them as those asbestos brake shoes wore out quickly hauling a couple of tons of steel down to a halt.

Honda Super Hawks, with their 200mm dual leading shoe brakes, were the epitome of motorcycle brakes in the 1960s. Those brakes were often pirated from dead bikes to be used on roadracers or even other street bikes whose brakes were poorly chosen for their stopping tasks. Despite all the hoopla surrounding the disc brakes on the CB750s, their single piston brake calipers really didn’t do a decent job of slowing down a 500+ lb street bike from high speeds. Even worse, the first generation CBX models had similarly insufficient braking for a 600 lb street machine with 130mph speed potential.

Today, we have ABS brakes available on even the smallest street bikes and even pedestrian scooters. Brake calipers have at least 2 pistons each and extreme cases all the way to 6 piston stoppers. Finally, tire technology has had to rise to the occasion in order to cope with the tremendous braking power available on today’s models.

It is hard to find a motorcycle shop now that has mechanics who understand the functions of carburetors and point/condenser ignition systems. Electronic fuel injection has recently been available for even 50 cc model machines in many markets. Troubleshooting and re-jetting carburetors has become a lost art for many mechanics of this generation.

In the past 25+ years, I have published helpful books and electronic media information to help carry what I have learned to future generations. I originally typed my first books on a word processor machine and then printed out the masters to take to a copy shop for reprinting into paper books for sale. That process worked well for about 10 years before I was able to get my hands on computers with some real fire power that allowed sharing of more and more information to more and more people in the world. Now I can offer thousands of pages of information via a download to just about anywhere in the world at a moment’s notice. Yes, the world has changed a LOT in the past 70 years…

I appreciate all the positive feedback from readers through the years. I continue to learn more new facts and nuances about the 250-305s and plow that information back into my offerings. I welcome questions about the vintage Honda models and can usually offer an answer from my experience or will find out what an answer might be from friends and other enthusiasts.

So, to all my readers: Thanks for the memories and support, in our combined search for the answers to our technical questions and discovering the history of these amazing vintage bikes.

Bill Silver 

aka MrHonda

Time flies, whether you are having fun or not…

Dear readers,

My apologies for failing to update this blog recently. I have had quite a lot going on wrangling my 1997 Dream 50 street bike and the Rickman CR750 project bike, of late. In addition there are the transient repair jobs that come in and out of the shop that tax my patience and shop space at times, too.

The little Dream 50 street bike arrived a few months ago, packed with a built from scratch 89cc race motor, featuring a dry clutch conversion, race head and cams, HRC crankshaft and 5 speed transmission. The head was ported and a monster 26mm Keihin CR carburetor adapted to the cylinder head. The engine was built with a new set of cases and all fasteners, which caused a problem with registering the bike in CA. California requires engine numbers for the titles and the new engine had none.

The bike did come with the original 5.5 horsepower stock engine, which was restricted by various methods. The cylinder head had a small 16mm port leading to undersized valves. The carburetor was a 16mm Keihin, tied to the stock air box. Honda’s CDI ignition system was married to a transmission switch that sensed when the bike was in 4^th or 5^th gear. The spark timing was limited in the top two gears to prevent the bike from exceeding 36mph (60kph) speed limit which is imposed upon 50cc motorcycles in Japan. Additionally, the front drive sprocket has only 12 teeth, which is the same as a Z50 mini-trail model. A little digging around on eBay turned up 13t and 14t options, however.

It is sad that a bike with such flashy good looks and disc brakes on both wheels is so restricted, but of course there are ways around those issues, which have been shared on the internet over the past 20 years. One of the gear indicator leads had been rewired with small little resistors between the wires to over-ride the speed limiter functions in 4^th and 5^th gears.

The stock cams top out the power output at about 10,500 rpms, despite a 13,500 rpm redline on the tachometer. An XR75 20mm carburetor was acquired from an eBay seller, which is a bolt-on for this bike. Jetting wound up in the #85 range vs. #75 for the stock 16mm carburetor. With all else basically in a stock configuration, the bike will tach out to 13k in 4^th gear burying the speedometer needle to approximately 60 mph on a long downhill run with a 14t front sprocket.

When the stock engine was reinstalled to get the registration accomplished, the 89cc big bore kit was installed on the engine, using stock cams and the 20mm carburetor. While displacement increases are always helpful on small-bore engines like this, the compression ratio was 11.6:1 and kicking it over was quite a chore, given that the kickstarter system was designed for a 50cc piston at 10:1 compression. Eventually, the bike was reassembled back to stock 50cc size, still keeping the larger carb in place. So far the engine has been out of the bike three times!

Getting a JDM Honda motorcycle registered in CA isn’t always easy, however the combination of having an Indiana title and the fact that the bike was less than 49cc allowed an over-ride in the CA registration system and a fresh CA title and license plate were issued to me for the little tiddler.

The bike was offered up as a package: stock bike along with the race motor and a lot of rare spares on eBay. The auction page count was nearly 2,000 with over 100 watchers, but failed to rise above $6700 at the end. After that, just the race motor and other racing parts were offered as a separate package, which drew several hundred page hits and over a dozen watchers, but no bids at the end.

The bike may wind up in a trade situation for a 1964 CB92 Benly Super Sport deal soon, but that hasn’t been finalized. As beautiful as the little Dream 50 is, its overall usefulness is limited for the type of riding that I hoped to be able to use it for, locally. Perhaps my expectations were overly optimistic for a 50cc bike that I outweigh by 10 pounds. I have fond memories of owning a 1970 SS50 which was brought in from Japan when I was in the USAF. That bike was always capable of 60mph in dead stock form. It is funny that with the passing of time and the improvements in technology haven’t yielded a faster machine than that little 2-valve horizontal single in the SS50, dating back 45 years.

Reviving more dead and dying bikes…

In the past few weeks, another parade of lifeless motorcycles has come through the shop and each one had various unique challenges and surprises, in some cases.

CB550-78

This bike has been a thorn in the side of the owner and me for a year or so. The bike was only used in the summer months, so sat for long periods with a half-full tank of alcohol gas and a weak battery and charging system. After a new battery was installed, it didn’t seem to be getting a good charge, so a new solid-state reg/rectifier was tried out but was either a defective unit or just not the right type for that old school design. Putting the old parts back in carefully seemed to have awakened something and then the bike ran well for a few weeks. Then there were misfiring problems that lead to a house-call where I discovered a loose ignition wire connection that seemed to have solved the problem. I didn’t test ride the bike, though and a few weeks later the owner complained that the bike would be hard to start, run awhile and then the battery would seem to discharge again.

The bike was brought to me this time and I dissected the charging system once again, but found little to fault. I quick test ride left me stranded about 6 blocks from home, though. I walked the bike back to the house and checked for fuel to the carbs, as the battery got run down from trying to restart it after it died down the street. It turned out that the owner had drained the old gas/rust/water out and put 1 gallon of gas back in the tank, without telling me. When the petcock was removed the reserve function was plugged up so it wasn’t supplying gasoline to the carburetors. Arrrgh!

The petcock was cleaned, tank rinsed out again and 3 gallons added to the tank. Once the battery was re-charged the bike fired up sluggishly, but did run okay once it was warmed up for a few minutes. Using carb spray, some air leaks at the manifold/cylinder head junction were discovered. The manifolds didn’t appear to have failed, but it was decided to change both the o-rings and manifolds as long as it was all apart. The battery was again charged up to where it was holding about 12.5 volts at rest.

Changing out the manifold o-rings and manifold connectors was not a particularly fun task with the carbs and airbox in place, but using some brute force was eventually accomplished. Using full choke, a cold engine start was initiated and the bike barked to life much more quickly than before. The lack of air leaks and subsequent resetting of the idle mixture screws brought the 29k mile engine to life at all engine speeds. When the battery started out at 12.75v in the beginning, it remained at that voltage level after a 15 minute test ride. These bikes have instant ON headlights, so the battery drain starts as soon as the switch is turned ON.

Speaking of ignition switches… the ignition switch base cover was not securing the switch base contacts to the rest of the switch assembly. Pulling the headlight loose from the fork ears gave access to the switch mounting bolts and the whole assembly was unplugged from the harness. The aged harness connector was getting brittle, but still had enough strength to hold the switch contact connector securely. It appeared that someone had tried to replace the switch base cover previously, but the slots where the cover snaps into the switch base were still plugged up with remnants of the original cover tabs. Clearing the tab holes allowed a new cover to engage the switch housing base correctly and securely.

When Honda started putting the ignition switches up in the middle of the instrument cluster, problems have arisen in the older, hi-miles machines where the constant push-pull of the harness wiring as the handlebars are turned back and forth causes the switch base and cover to work loose. When the connector separates just a little bit from the switch base, power is interrupted or lost altogether.

The combination of a loose ignition switch base, lack of fuel, weakened battery from excessive cranking caused a whole cascade of problems that the owner was experiencing. After chasing out the gremlins and getting the bike running properly, attention was made to the rest of the bike which had run out of rear brake adjustment threads due to worn shoes. Replacements were ordered and installed, so now the bike’s owner has a better chance of riding a bike that operates correctly and is safe to ride for the summer.

Two more dead ones…

A good friend from Los Angeles brought down a long-dead 1967 Honda 305 Scrambler and a 1982 Honda Z50R Mini-Trail bike for revival. John had owned the bike for more than 25 years, buying it for its overall originality (some restoration work was done) and had never really ridden it. The Mini-Trail 50 was destined for his grandkids once it was brought back to life again.

The 305s are my specialty, so generally no surprises there, but not many Z50Rs have come my way in the past 30 years. Basically, they are about as elemental as you can imagine, but this one had me scratching my head for more than a few hours as repairs were made and tested.

1982 Z50R

Most of the little 50-70cc Honda singles have a simple magneto-ignition, a compact OHV cylinder head and tiny single carburetor, running an automatic clutch to make the package operate under the normally grueling conditions that are the life for Mini-Trail motorcycles. I was given a tune-up kit with the Z50R, consisting of a new spark plug, ignition points and a condenser. Removing the flywheel was the first order of business and that uncovered a magneto that had either been run uncovered in the dirt or just stored in a very dusty and moist environment for many years.

The inside of the flywheel, where magnets are located was coated with dust/rust which made the transfer of electrical energy impossible. The magneto base was similarly coated with dirt on every surface. The condenser wires are soldered onto the top of the unit, so you have to unsolder the old one first. Transferring the wire connections can be tricky if you have a cold solder joint or the wire ends are not tinned properly. The tune-up kit was an aftermarket brand whose parts fit the engine, but were really not all of the quality of OEM components.

Once the magneto base was cleaned and all components installed the flywheel was fitted for testing. Unfortunately, there were no signs of spark initially, so the flywheel was again removed. A closer look showed that the primary ignition coil base has rusted ends, which again work as an insulator against the effects of the flywheel magnets. Once a careful cleaning of the coil posts was completed the ignition finally showed signs of life giving off a nice little blue arc across the spark plug gap.

The carburetor was removed and found to be remarkably clean, however the pressed-in pilot jet appeared to be blocking fuel flow due to residue inside the .014” hole. The jet was twisted, pulled and finally removed for inspection and cleaning. Tiny tapered reamers were used to clear the passage, but when the jet was pressed back into the carb body, the fuel flow remained blocked.

With the jet removed once again, it appeared that the feed hole in the carburetor throat was drilled slightly off center, so that the blunt end of the jet was blocking fuel delivery. The end of the jet was beveled a little, but flow problem persisted to the point where the engine would run, but idle mixture flow was uneven, causing the spark plug to fuel foul leaving black soot on the electrode end. The engine would either not idle or would suddenly speed up to a fast idle. Mixture screw adjustments had little effect on the condition and finally a new carburetor purchase was made to eliminate what seemed to be the running problem.

The fuel tank was initially viewed as “amazingly clean” at first glance down the filler hole. When the tank was removed and the petcock unscrewed from the fitting, a little rain of rust particles poured out of the outlet. It appeared that some water/moisture had settled down at the bottom of the fuel tank, causing rust flaking to occur. It never was enough to work its way up towards the opening so at first glance, it appeared to be a clean tank. Rust bits were knocked loose and a new petcock installed with a screen to prevent rust from coming through the fuel lines and carburetor float valve.

These little engines often suffer from little or no maintenance, so the typical reason for them to be discarded is that no one has ever adjusted the valve clearances. The clearance is only .002” so over time the valves sink slowly into the seats and the result is compression loss, with hard starting and poor performance issues. Adjusting the valves often brings them back to life without a lot of extra work involved.

This bike was showing a bit of oil smoke in the exhaust, so the cylinder head was removed (requires front tire removal!) and the valve stem seals replaced and valves cleaned of old carbon deposits. In the end, the compression readings were over 150 psi, which is great for these small engines. With a new carb, correct ignition timing and fully functioning cylinder head, the bike now starts and runs well.

1967 CL77

After an initial visual inspection, a big parts list was initiated including new air filters/tubes, spark plugs, carb repair parts, new cables, replacement hardware for the missing brake light switch and centerstand hardware to replace the undersized stand pivot bolts and a very long coiled spring that wrapped around the swing arm. The correct centerstand hardware consists of two special pivot bolts, a spring hook and short coil spring. The brake light switch stopper mount had been repaired using a small flat washer, tack welded into place. The switch bracket is welded onto the frame and this one was bent up at about 10 degrees from normal. While changing the rear brake cable, the brake arm was slow to move indicating that the brake cam lubrication was gone and corrosion was taking its place.

So, the rear wheel was removed to service the brake cam problem, only to find that one of the brake return springs had a broken end, so was just hanging inside the hub ready to fall into the drum at any time. New springs were ordered and the brake cam removed, cleaned and lubricated for normal function. The front wheel will need the same service as the brake cable pulling the brake arm is mostly non-responsive. The brake cams were sticking and the brake linkage had been installed backwards. These are the kinds of things that you must expect on a 50 year-old bike that has been stored for more than half of its life.

With overhauled carbs, petcock and new air filter assemblies, the bike was nearly ready to start back up. Fortunately, this gas tank WAS REALLY CLEAN inside, which is nearly unheard of given its age and storage situation. Compression checks were a bit under specs at about 120-130 psi, but that is enough to make them start and run. Often there is a thin layer of carbon or rust on the valve heads and seats which prevent a positive valve seal in initial running. Once the bike began to run, the engine sounds improved in the quality of exhaust tone and I suspect that valve sealing will improve with time and miles.

The ignition timing was somewhat close enough to run, but dynamic testing showed an over-advance condition on the left cylinder. The bike idled low enough to establish running idle timing before the spark advancer kicks in and kicks the spark timing up to the 45 degree (II) mark. With some 12k miles on perhaps the original engine, the internals are bound to be worn to some degree. The central camsprocket carries the spark advancer plate, weights and return springs, which are subject to wear and loosening of the rivets that hold the whole assembly together at those mileage markers. 

The spark timing was established correctly, but the engine tends to want to rev up and then return rather slowly. Often, this is due to the carb slides sticking or throttle cable routing problems. New o-rings were installed on the carburetor flanges and insulators, so the manifold air leaks should not be an issue which could contribute to uneven throttle response. For reasons unknown, the main jets installed on the carbs were #120 vs. normal #130 mains. With today’s alcohol-based fuels, even larger jets might be required.

The handlebar upper clamp was cracked in the center, which was a first for me to encounter. A new OEM part was ordered from eBay sellers and was to be installed when a rather shocking discovery was revealed beneath the cracked part. What appeared to be OEM Honda CL77 Scrambler handlebars are probably those made for a CL350-450 model, which have a wraparound reinforcement in the center section. The handlebar clamp has no provisions for this raised section, so it was no wonder that the part cracked when the bolts were tightened down.

Instead of replacing the bars, the ends of the existing clamp were cut off and made into individual pieces which secure the handlebars and clear the raised center section of the installed unit. This is a bike that is FULL of surprises. While much of it appears to be original, it has obviously re-plated wheel rims and a few other chrome pieces. 

This bike is one of the later 1967 models, which feature chromed front and rear fenders, plus the oval-shaped tail light assembly.  A replacement lens was purchased to repair a broken stock lens on the bike. Other repair issues include a stripped out frame bolt hole which is used to secure the exhaust system to the chassis via the long, special 10mm head mounting bolt. Honda Scramblers are well-known to vibrate and loosen various parts along the entire motorcycle, so this was not a big surprise, but the repair of a shallow blind threaded hole is challenging.

There are well over one-thousand parts on a vintage Honda twin and each one has a purpose and function. This is another one of those “surprise” bikes which had been partially repaired/restored by someone who was certainly creative, but not one who went by the book on ordering and replacing damaged parts with OEM equipment. These are the challenges that many mechanics and owners face as they try to revive 50+ year old vintage Hondas. One must be patient and diligent in looking at all the parts and pieces during the rejuvenation process.

Bill Silver  aka MrHonda

Not so nice CB 200T mystery machine…

It seemed innocent enough at the time. I was referred to a new customer who had a relatively low miles CB200T street bike that was set aside after extensive carb and petcock cleaning hadn’t solved the bike’s running problems. Apart from a new coil installed there were apparently no other modifications done to the machine other than a set of EMGO mufflers that replaced the rust-prone originals. How hard to it be to get it running again?

It had been sitting for close to a year, apparently, so the battery was stone-dead and needing replacement. Once the neglected machine was brought back to the shop, a new battery and some spark plugs were picked up at the local dealership and a few checks made on the overall condition of the bike and engine. The compression readings were both right about 150 psi, which is on the low end of specifications, but should have been good enough to make it run okay. These are not overly-powerful machines, but should run up to redline in lower gears without issues. 

After experiencing a “wrong coil” issue with a CR93 Tribute bike a year ago, the first thing to check, once the fuel tank was removed, was the new ignition coil. Honda’s OEM coils are no longer available, so you have to go with the only available options; new aftermarket coils made in China.

Sure enough, when the coil was checked with an ohmmeter, the primary side resistance was 1.5 ohms, instead of the normal 4.5 ohm readings for a bike with points and condenser ignition systems. I ordered a correct 4.5 ohm coil and looked over the fuel system while I waited for the ignition coil to arrive from SFO distributor 4int1.com

I expected to see a set of reversed carburetor slides as a possible contributor to the reported problems, however they had been installed correctly. The needle clips were in the middle position and the needles were K marked OEM parts. Very often carb overhauls are done with aftermarket branded kits which have poorly engineered replacement parts, but this was not the case here. Despite laying up for many months the carbs and fuel tank petcock were still fairly clean and not obviously causing problems.

When the coil arrived, I installed it and screwed the spark plug caps into the wire ends, which were NGK branded parts. The bike fired up with the new battery, even on the old fuel, but the engine stuttered and balked as the throttles were opened much past half way. The engine sounded like it was choking from excessive fuel, so it was shut back off and the float bowls removed for inspection of float levels and any blocked air passages. The right side bowl came off only to find the idle jet lying in the bottom of the bowl! That explained the over-rich condition that had carboned up the spark plug on that side. The jet was reinstalled and fresh spark plugs installed. The bike restarted, sounding better, but still had a mid-range stumble. The plugs were removed for another look and it appeared that the engine was still running somewhat rich. When the plug cap was removed, I was startled to see that the inside of the spark plug cap hardware was still stuck to the end of the spark plug! Well, that would explain some misfiring!

These small Honda twins have a single, dual-lead ignition coil, so both spark plugs and caps must be secured to the spark plugs in order to fire properly. An open circuit on one end or the other causes the spark to break down immediately. New plug caps were purchased and installed after the plugs were cleaned and the bike restarted once again. More blubbering sounds were apparent and this time the left side carburetor’s idle jet was discovered to have had unscrewed itself and was lying in the bottom of the float bowl! The jet was still open, so was reinstalled again and the start-up routine repeated. The bike would start and run okay, but continued to mis-fire beyond mid-range throttle openings. Now what???

Going back through the ignition system, I checked the ignition points contact faces, which were a little dished from wear, so they were cleaned up and re-gapped to specifications. The spark advancer was checked for proper advance/retard functions and some point cam lube applied to the advancer cam surface. The ignition timing was reset to the F mark and checked on both lobes of the point cam. The opening of the points was within a degree or two of each other, so well within reason. The voltage was checked on the points when the engine was off and then running. Initially the point voltage readings were around 9 volts, but then climbed back up towards 12 volts as the engine speeds were increased. Typically, the ignition voltage should be close to battery voltage, however these 1975 and later twins have “always ON” headlights, so there is an immediate voltage draw when the ignition switch is turned to the ON position.

I opened up the headlight shell to check the wiring color matches and found the black/white stripe power lead for the kill switch (which feeds the coil) plugged into a rogue brown wire, normally used for lighting purposes. Shifting the wire back into the 4 way black connector gave a better voltage reading, however the headlight feed was also plugged into that junction. The right side handlebar switch was not the correct one for this application and normally has a blue white stripe feed going into and out of that side. The wiring was not present in the switch, so the feed wire had to be plugged into the main switched black wiring junctions, as well.

The bike was test-ridden numerous times in the local area, but no matter whether it was going downhill or uphill under load, the same high-speed cut-out misfiring remained.  I rechecked the fuel and ignition systems once again, eventually replacing the ignition points and condenser, although they really didn’t appear to be defective. Most of these components are relatively inexpensive, but I don’t like to keep throwing new parts into a bike as a process of elimination to cure a problem. After many hours of checking and rechecking everything from the gas cap venting to possible muffler back pressure issues, nothing new was found. 

The remaining clue was that when a dynamic timing light was connected to the spark plug wires, the light flashes started to become intermittent when the engine began the mis-firing routine again. Despite the presence of a “new” ignition coil of the correct impedance, the symptoms continued to indicate a failing secondary voltage issue at the plugs.

In desperation, a hopefully good used OEM Honda CB200T coil was purchased from eBay sellers to prove or disprove whether the misfiring is still coming from the coil or some as yet undiscovered nuance which has not been recognized. The coil arrived in just a couple of days and I was holding my breath about whether this really was the final solution to the mysterious misfire…. Honda coil installed and the bike went right to redline without any hesitation….. a LONG and winding road leading to my first inclination that the “new coil” from China was not up to specs. Apparently of the 100 or so that 4into1 has sold, I got the bad one!

Well the bike has been gone over with a fine-tooth comb and is now ready to return to its owner, ready and raring to go once again. There is no way I can get reimbursed for all of my time expended on this repair, but I have the knowledge that my troubleshooting observations were ultimately correct. Another day at the office at Casa del Honda.

Bill Silver aka MrHonda

www.vintagehonda.com

Minutiae; It is all in the details…

Recently, I had a call about a local CL72 owner who was seeking help for his 1965 model Scrambler, which was having numerous performance problems. He was located in N. San Diego County, so I referred him to my friend Randy Troy, who lived just a few blocks away. Randy has had years of experience in working on all kinds of Hondas and was trained as a Porsche mechanic and worked at a Datsun dealer back in the 1970s. He has a deep understanding about the “how’s and whys” of how things work, but had never been hands-on with a 250-305 Honda twin before.

He began with a basic tune-up to get it up and running, but encountered problems right away. The carburetors would fuel foul the spark plugs quite quickly, so the first thing he did was to remove the carburetors for inspection and cleaning/adjusting. If you have worked on any Honda Scrambler, you know what a PIA it is to get to that left side carburetor for any kind of service or removal. In the past few weeks, he’s become proficient in doing that job!

With the air filter tubes off, he was watching fuel spitting back into the inlets, even at idle, which is never a good sign. The compression readings were about 130 psi, which is about 20 psi low. This generally indicates that the cam timing is slightly retarded (a half tooth, which is remedied by changing a tooth on the crankshaft, not the camshaft). Sure enough the cam timing was off. Fortunately, only a CL72-77 allows for the top engine cover to be removed with the engine in the chassis, which allows for cam timing verification and adjustment. 

With the top cover off and spark plugs removed, the first thing to do is to anchor the head/cylinder to the engine cases, by putting some short  sockets on the studs secured with some nuts. This keeps the top end from lifting when you turn the engine over. First you have to locate the master link on the camchain, then carefully disassemble it and string some wire through the ends. Loosening the valve adjusters takes the camshaft lobe load off the cam, so it can be positioned in a way that the flats on the camsprocket are level with the top of the cylinder head.

Once the cam position is set, you have to jiggle the crankshaft around with the camchain ends held in such a way as to allow the crankshaft to bring the right piston up to TDC AND the ends of the camchain towards the top to reattach the master link once the timing is set. There is a lot of fiddling around to get this all to happen, but Randy did achieve the goal and the cam timing was back to where it belonged. 

Once that was done, then the carbs got a long look. Randy noticed that there was wear and corrosion on the needle jets that might have caused some fuel spray problems. He was lucky to find a new set of needle jets at David Silver Spares, which arrived in a few days. Then he mentioned the other calibrations of the jets, which were not quite correct. He found #120 main jets and #40 idle jets in place of the normal #115 mains and #38 idle jets. On top of that he read out the needle codes, which turned out to belong to a CB72, not a CL72. The CB72s have a “power jet” fuel enrichening system which calls for a different needle taper. Stock OEM CL72 needles are NLA now so Randy had to order the oft-maligned Keyster carb repair kits, which come with new needles, float valve, gaskets, etc.

Keyster kits are made in Japan, but have been found to have incorrect metering needle tapers and poorly fitting float bowl gaskets in the past. When the kits came in the gasket issues apparently remained and the needles were of a different taper than the CB72 needles, so that might be a solution for the rich running. With new needle jets and Keyster needles, the bike ran too lean off the bottom end, but the fuel backflow problems at idle were solved. The needle clips were lowered to the bottom notches in order to richen up the transition from idle through mid-range, which improved fueling somewhat.

Randy also learned about the ignition timing vagaries associated with having the camsprocket controlling the spark advance curve. He set the initial ignition timing statically with a 12v test light, but discovered that running ignition timing often does not reflect the initial settings. In order to prevent over-advancing the spark timing, the idle timing had to be retarded back towards the T mark instead of the F (firing) mark. 

Changing the ignition timing alters the vacuum signal to the carburetor metering systems, which causes the mechanic to have to alter carburetor mixture and idle speed settings. The ignition timing and carburetor settings are inextricably intertwined and there is not that much you can do about the ignition timing without tearing the cam shaft sprocket out for repairs or replacement. There is inherent slop and inaccuracies with this camshaft driven ignition system that cannot be completely overcome with a used engine.

With new carb parts, many of the performance issues began to subside, but Randy feels like the bike is still a little bit flat in the mid-range, so he bumped the main jets up to #125 to see how it worked; especially when jetting for today’s alcohol-blended fuels.

After all this intensive work to exorcise the demons of this bike, his test rides have highlighted a 2^nd gear jumping out issue, which requires an engine removal and cases split to remedy the transmission woes.  Carb jetting is still a bit off, mostly due to a lack of available OEM jet needles for a CL72. Sometimes you just do the best you can with what you have and then give it back to the customer highlighting the known remaining issues and an estimated cost to fix them properly. Randy probably got paid about half of what the job was really worth, time-wise, but he was appreciative of the chance to learn all about the mysteries of the 250-305 Honda twins.

To paraphrase Forrest Gump’s comments: “Vintage Hondas are like a box of chocolates; you just don’t know what you are going to get.”

Orphan Exchange; a twin for a single

Those who know me well are aware of my fondness for the Kawasaki W650 models, which were only sent to the US market for two years (2000-2001). I have owned three of them over the past 9 years, with two 2000 models and the last one a desirable 2001. The 2001s had some subtle changes to the front axle, steering head angle, rear fender and were painted a lovely two-tone Dark Green over a Cream bottom portion.

Due to a plethora of bikes that have been coming and going in the past year, I decided to let the 2001 bike go and advertised it on the local Craigslist as well as once on eBay, but with no results. The bike only had 9k miles on it, was all dialed in with carb jetting and suspension upgrades and was driven briskly on Sunday mornings with my friends the Jamul-igans. With skinny tires and forks, plus about ½ of the other’s horsepower ratings, the bike was driven hard, but not abused. Previous crash damage was mostly all repaired; leaving only a few spots of scrapes and paint chips. It put a smile on my face every time I drove it, but it was a bit too big and ungainly for quick trips to the local Post Office or auto parts stores. Historically, I don’t keep vehicles much longer than a year or two, so the time was up for this fine machine.

Most of the Craigslist responses were scammers trying to get my email address or phone number for nefarious purposes, but one reply came from a man in Rocklin, CA (550 miles from Spring Valley) who was “ready to buy” and even considered flying down and riding it back home. The only holdup on his plan was that he was trying to sell his 1990 GB500 TT bike, which was somewhat weathered and had 29k miles showing on the speedometer. The sales efforts were non-starters for various reasons, so after we exchanged messages back and forth for a couple of weeks, I decided that I would offer a swap; his GB500 for my W650. He agreed to meet me “half way” between SV and Rocklin at Visalia, CA, where my cousin has lived for over 40 years.

The photos of the GB500 were less than detailed, but I figured that a licensed, running GB500 with mostly all original parts was equal in value to what I was trying to get for the W650. So, one Friday morning, at 4AM, I launched my Toyota Tacoma up the I-5 with the Kawasaki W650 secured in the bed. The plan was to get through LA traffic before it became unbearable during rush (?) hour. I had agreed to meet up in Visalia at noon time, to give us both plenty of time to arrive at the destination. Well, my plan was a little too optimistic, perhaps, as I arrived some 300 miles from home at 9:30AM!

Texts from the GB500 man indicated that he didn’t leave Rocklin until 6:30AM, which took him right into downtown Sacramento traffic at 7AM, so he was delayed quite a bit on his end of the journey. 

In the meantime, I spent time with my cousin who owns a thriving auto repair shop in Visalia and is a real “gearhead” kind of guy, owning a couple of 1960s Mopar drag cars equipped with Hemi engines, as well as an airplane and some pricey automobiles and trucks. It was great to catch up with him during my 3 hour stay, but I finally decided to leave the shop for the rendezvous near the Highway 99 Junction which was about 8 miles away. While I was driving, he sent a text indicating that he had taken the wrong off-ramp and was turning around to the intended location. As I came upon that same off-ramp, I looked ahead to see his car (Honda Element) just getting back on the freeway. I went back on the freeway ramp and followed him right to the Chevron station that we had agreed upon as the meeting place. Good timing!

Yes, the GB500 came down in the back of a Honda Element SUV, actually fitting in quite nicely. We unloaded our bikes, took a quick test ride to confirm that this is what we really wanted to do, then swapped bikes into each other’s vehicles, completed paperwork and headed off for home, once again.

I was a little disappointed with the overall condition of the GB500, as the alloy parts were mostly corroded, however most of the chrome plating was relatively clean. Apparently the bike lived in Oakland for awhile, near the bay and was obviously ridden a great deal in the past 27 years, so wear and tear is expected to a certain extent. My biggest concern was the noises coming from the engine, as it was fired up cold. It was hard to pin down the specific area of the engine where the noises were occurring, but it was a bit unnerving to say the least. The bike ran fine on the test run, so I just decided to go forward with the deal and fix whatever was necessary later on.

I ran back down the 99 to the I-5 junction, then up over the Grapevine pass to the 210 highway junction, which I took to my friend Myke’s place in Sunland, CA. The total mileage covered for the day was about 500, all in 13 hours. I enjoyed some rest and a nice Thai meal nearby and went to bed planning on an early start on Sat morning, in order to miss the always busy southbound freeway traffic headed into San Diego.

I launched at 6:30AM and headed way east towards the I-15 southbound, where traffic was racing along at 70-85mph, making the return leg of 180 miles in 3 hours. I unloaded the bike, unpacked and then stripped the tank off of the bike to see what was underneath the bodywork and perhaps pin down the source of the engine rattle. With the help of S100 cleaner and a hose, I was able to clean the bike up pretty well, followed by a blow-dry session with the air compressor.

I checked the valve clearances, which were just slightly loose and attended to an odd oil leak that was coming out of the center of the rocker arm cover. The bolts for the cover are all supposed to be dry, so I was able to squeeze a little 8mm o-ring over the bolt head (it was too long to remove with the engine in place) and then retorqued the bolt, hoping for an effective repair of that problem. I finished up by installing a fresh spark plug and removing the rest of the pollution control devices and hoses which were partially taken off by the previous owner.

Both tires were under 20psi, so I aired them up, checked the oil level and the chain tension and headed out for a test ride around the neighborhood. The bike ran well and was responsive to the throttle, but the clamor coming from the engine continued to puzzle me. I decided to take the GB500 on the Sunday ride and see if it would break something or if the noises were just excessive piston slap on a 92mm wide piston, churning up and down with a redline of 8k rpms.

Well, the Sunday ride went well and I thrashed it as much as was reasonable under the circumstances. Unfortunately a prior owner installed oversized tires on both ends, so a good deal of caution was taken not to get them way out on their sidewalls. The tires are Bridgestone BT45s, which are grippy things, but these were getting sidewall cracks due to age.

Back home, after the ride, I did research on the GB500 noise problem and found a detailed webpage that described having to replace the piston at 27k miles on his machine, plus he rebuilt the crankshaft with a rod kit which is available. The engines are related to the early XL/XR500-600s, so some of the parts will interchange. Supposedly, the 97mm XL600 piston and cylinder will mount up on the GB500 cases, giving a 100cc displacement increase. Other models use a 100mm piston, but that is probably really pushing it, unless you do a full-on rebuild.

Top end teardown

After the successful Sunday ride, I decided to drain the oil and pull off the top end to see what might be causing some of the noises inside the engine. Fortunately, the top end can be removed with the engine still in the chassis. You can pull the head off and away from the carburetor/manifold/air box with those components all safely in place.

The top cover has the rocker arms all installed and the first bit of bad news was that both of the exhaust rocker arm pads were worn down excessively. The good news is that the intake sides were all just fine. The center of the cam runs directly on the cylinder head bearing, which is oiled by an oil feed hole in the camshaft. The cylinder head side was scored and roughed up like the exhaust rockers, but the top cover bearing surface was like new.

After figuring out how to extract the camshaft from the sprocket and two ball bearings, the head was ready to remove. There didn’t seem to be a lot of deposits or moist carbon on the valve heads or the piston crown, as if someone had been in there before, freshening up the internals. Sure enough, despite a lack of markings on the piston, the piston rings had .25 marked on the edges. The piston didn’t show any signs of distress or a great deal of wear. The cylinder bore still had nice cross-hatch marks on most of the surfaces, but when the rings were removed from the piston and stuck back into the bore, the end gap was .025” to .035” on the two top rings. Normal specs are about .012” to .016” using the standard reference of .0045 inches of end gap per each one inch of cylinder bore. I had my machinist friend measure the piston and bore size accurately and he determined that the piston clearance was about .003” which is near the wear limit of .004” that Honda recommends. He felt that the piston clearances were not sufficient to create the kind of engine noises that I was hearing.

With the 24mm piston pin removed from the piston and refitted to the rod end, it was evident that there was enough clearance to give a loose rocking fit to the pin in the rod end. Most likely, this is the main source of the engine noise. The remedy is to install a $125 rod kit in the crankshaft, once the engine is pulled all the way apart and a machinist presses the crank apart and back together again with the new rod kit. Not what I had in mind for this little bike project.

All apart…        

The bottom end was pulled out of the chassis and put on the bench for disassembly in order to replace the connecting rod in the crankshaft. There are several locking nuts inside to secure the clutch hub and other critical components, which needed a 24mm socket and air wrench to remove. Once the locking nuts were removed, the rest of the engine more or less melts apart into transmission and counter-balancer units along with the huge ball bearing which supports the crankshaft in one case half.

While waiting for the arrival of the connecting rod kit, cleaning and some painting was done to the top end components, along with replacing the valve stem seals in the head. The valves were de-carboned and the combustion chamber cleaned up of old burned oil residues. The inside of the engine was quite clean, so regular oil changes must have been done in the past 27 years. New gaskets and seals were procured via the Internet, but it was surprising how few parts are left available for these bikes now.  A SoCal dealer had a new set of .25 oversized rings, which when checked in the cylinder bore did show a reduction in the end gap measurements over the old ones removed.

A local camshaft manufacturing shop felt they could regrind the lobes without having to dig too deep into the base circle (schneidercams.com) so they took the old camshaft in for a couple of week wait in their queue. New OEM rocker arms were purchased through the local Honda dealer, so the major pieces are coming together finally.

Because of the miles on the bike, a decision was made to buy an aftermarket starter motor repair kit and freshen up the starter motor before it was returned to the engine cases. Once apart, there was very little wear showing on the brushes, so the kit was left unopened and will go with the bike to the next owner someday in the future.

The carburetor still hung in the airbox, so it was an easy task to remove the throttle cables and enrichener, loosen the clamp and remove the whole carb as a unit for cleaning and inspection. In all likelihood the carburetor had never been serviced as it was still jetted to the CA spec 142 main jet size. I didn’t have any 145-ish jets handy, so used my tapered jet reamers to open it up more towards a 148-150 size. With a fresh motor, use of alcohol-based gasoline and the possibility of a slightly modified camshaft grind, a little more fuel is generally a good step towards improved performance.

The crankshaft was taken to a local machinist friend, who found difficulties in attempting to remove the crankpin from the assembly due to a close-fitting sprocket pushed up against the crankshaft cheek. Finally, he just pressed the easy side off and checked the pin for wear and damage. The pin checked out fine, so the new rod was installed and the crankshaft pressed back together again. Finally, he had to gently press the crankshaft back into the engine case half to complete the job.

With the crankshaft done, assembly work could resume and all the little bits and pieces reinstalled where they belonged. 

I had the unfortunate experience of buying an “Engine bolt kit” from an eBay seller which appeared to be a complete kit, but was found to be missing the crankcase bolts. Emailing back to him was frustrating as I was told that if I had “read” the details I would have seen that the crankcase bolts were not a part of the “kit” and were available at an extra, undefined charge. This was all buried in a dozen paragraphs once you hit the “SEE DETAILS” section. Why he chose to offer a “kit” without the critical center case bolts is a mystery and he never would say why he did it or why he didn’t list the price of the extra bolts in his auction. After some unpleasant exchanges, I paid an additional $25 for a handful of bolts, which the seller then cancelled and decided to block me from future business, leaving me without the final matching bolts to finish putting the engine back together with.

Another seller on eBay did offer the center case bolts as part of their main kit, but I only needed the few not a whole kit. His main website offered individual bolts and fasteners in an easy to use menu, so I ordered up what I needed from there and awaited delivery. It was a very frustrating experience to say the least and has held me up an extra week, just because the seller decided to play games with his product offerings.

In the meantime, the front brakes were addressed with a caliper rebuild, new pads and a fresh master cylinder kit installation. New BT45 tires were spooned onto the rims and fresh rear wheel dampers installed in the rear hub.

Drama and Difficulties

After several weeks, the cam grinding company discovered that they couldn’t grind the cam lobe next to the de-compressor parts attached, so took it to a nearby machine shop which took 2 tries to get the end pieces pressed off. Apparently they only had an arbor press not a hydraulic one. They finally get it loose, with the bits flying all over the floor. They claimed to have found them all but later on I discovered that the thrust washer was not in the bag of bits. With the de-compressor parts removed, they were able to grind the cam and Parkerize it afterwards. When I took it back to my local machinist friend’s shop we discovered the missing thrust washer. I ordered a new one from Honda, but the only ones were in warehouses back East and it took a week to get one out to SoCal. In the meantime I found that the oil filter washer from a CB750 was about the right size, so I used that when the parts were pressed back onto the end of the camshaft.

I thought I was near completion when I discovered that the funky cylinder head-mounted camchain tensioner requires a Honda special tool in order to retract the tension from the camchain guides. The tools are available for about $50, so I ordered one of those, too. In the meantime I tried to wrestle the engine back into the chassis by myself and fought it for more than an hour before it finally found just the right positioning to get the mounting bolts installed. The only other GB500 engine install I have done was when I lived in Hawaii and that time I wound up laying the engine on the floor and dropping the frame over the engine so I could get the alignment done. It is a total PIA and the frame tubes are all scratched up from the wrestling match efforts.  Apart from flywheel pullers, I have never had to use a special tool to reassemble a Honda engine until this one. Nevermore!

On the home stretch…

From the time the bike was picked up, it has been almost exactly 2 months of work and waiting to get the GB500 back up and running again. After several weeks of waiting the camshaft was ground, but the result was that the de-compressor gear really didn’t want to work with the re-profiled cam lobes, so the whole assembly was removed from the camshaft. Apparently only the US versions of these bikes had one in the first place, so no big deal to remove the de-compressor parts.

Just as I thought the end was in sight, the first firing of the engine revealed a pair of exhaust leaks. I had ordered the wrong head gasket (XR500, instead of the one for the GB500) and it didn’t have the extended sections to encompass the PAIR (pulse air) system transfer ports! It took another three hours to R&R the cylinder head gasket to repair the exhaust leak problem. Once that was finally accomplished, the bike fired up once again and seemed to be running well.

Several local road tests failed to reveal any major further issues, so the bike was taken out on our Sunday morning rides up into the mountains and back, about a 65 mile round trip. With scuffed in new BT45 tires, new front brake system overhaul and new pads, everything is getting a new break-in period, but so far it seems to have been a success in the end… but what a lot of work and expense!