Friday, November 24, 2023

 Too much friction spoils the party…

In bringing the CB350F back to life, I noticed that the forks were pretty stiff upfront. Hitting small bumps would just push the front end of the bike up like it was a rigid fork machine. The fork seals were leaking anyway, so I pulled the forks off, re-sealed them, and filled them with some synthetic ATF from the auto parts store.


Stiction: an abbreviation of “static friction” - the friction between stationary surfaces at rest, which resists them beginning to slide over one another.

Friction: the resistance that one surface encounters when sliding over another. Generally speaking with suspension this refers to “dynamic friction”, ie the frictional force while already in motion

Nothing was bent or damaged on either fork, but when the whole front end was reassembled, it still rode like an empty 1-ton pickup truck. I had already changed the worn-out rear shocks with some slightly longer aftermarket copies, but that didn’t do a lot to improve the ride quality.

My recollections with re-assembling 1970s Honda street bikes, even after a tire change is that the fender stay mounts are not precisely fitted and it has been my belief and experience that when you force the fender stay into the insides of the fork sliders unnecessary friction/stiction is induced onto the fork suspension system.

With the CB350F, I removed the front axle and nut, tightened them together, and then mounted one end into the bottom of the fork slider, secured with the two nuts on the cap. With both fork tubes set about evenly at the top of the fork crown, there was a gap of about a 16/th of an inch above one end of the axle in the opposite slider. I loosened the fork tube on that side and tapped it down until the slider just rested back on the end of the axle. This keeps both sliders at the same level, preventing binding on the fork bushings. See end photos.

Secondly, when I bolted the fender stay to the right side slider, opposite of the disc brake mounting hardware, a gap was clearly seen between the fender stay and the fork slider/brake hardware mount. I added two 6mm washers on the front bolt and one at the back to keep the fender stay from pinching the fork sliders together, causing fork bushing binding.

The front and rear fender stay bolts were loosened up to allow the ends to center themselves on the bolts. I also loosened up the fender stay mounting fasteners to the fender itself. The goal is to allow the fender to just float in between the fork sliders, moving as a unit up and down with minimum amounts of friction caused by side-loading the sliders against the fork bushings.

There are super slick fork seals, fork seal grease and fork oils that are all designed to lessen the friction and stiction in the front suspension. All of these things can help to allow freeer movement of the front forks during compression and rebound motions.

Honda and most other manufacturers were not fully cognizant of the dynamics of fork action in the 1960s and early-1970s, with most of them having little rebound control. Progressive wound fork springs can be helpful in allowing more initial movement of the front end when encountering small bumps. Changing the whole spring rate is sometimes necessary. Most bikes were designed with the maximum load rating in mind, which is generally too stiff for a solo rider of average weight.

Any or all of these things can cause fork binding that wears the fork bushings and inside of the fork sliders unnecessarily. Take time to carefully look at how the front forks and fender are fitted to the bike to minimize suspension travel problems.

Just refitting the front fender to the forks, as described above, allowed for a noticeable improvement in the ride quality on this particular bike.

Bill Silver aka MrHonda


Monday, November 13, 2023

It’s a DADs bike… 1973 CB350F revisited-Part 2

 Part 2

The bike didn’t stay intact for very long. I put it up on the workbench and proceeded to dismantle the bike’s exhaust and carburetors to allow the disassembly of the top end to find out what the source of the oil leak was and rather uneven running at idle. Visually, the tach drive seal had been leaking for a long time and drooling oil down the front of the engine.

As the cylinder head was removed, it became apparent that the head gasket had blown out between the number 3 and 4 cylinders. This is highly unusual in my experience, especially having raced 350 and 400F models under severe conditions. Here was a stone-stock model with a burned fire ring and adjacent gasket material. The combustion chamber was carbon-ed up, as were the valves with burned oil, but the cylinder bore looked completely fine and just like the other three.

The cylinder head had a depression and signs of some erosion from the blown head gasket area. I measured the depression to about .004” and sought out a machine shop that could shave off about .006” to flatten out the head and erase the low spot between cylinders.

I took it to a local automotive machine shop but they were unable to jig the head up in their machine, so they walked it down the street to another machine shop to see if they could do the deed. I suppose that you might be able to skim-coat some JB weld down in the valley and coat the gasket with some sealer to ensure a good connection, but that would be a last-resort effort. Certainly, another cylinder head would be available on eBay, but you never know what you will get in a used part like this.

Trials and Tribulations….

Well, the second machine shop did a beautiful job of skimming off just a bit of the uneven cylinder head surface, so all I had to do was to remove the rest of the valves, de-carbon them, change the valve stem seals and put it all back together again. Reassembly is pretty straightforward on these engines, which are easy to work on in the frame. After I got the top end back together and the valves adjusted, I checked the compression readings which were all about 150 psi. I left the pistons/rings alone as the bores looked pretty clean, but it does have 17k miles on it, so we’ll see how it runs and if it wants to use some oil. The valve stem seals were definitely cooked, so the new ones will reduce oil burning quite a bit.

The carburetors were split apart enough to replace the o-rings on the fuel fittings that feed gasoline across the four carbs from a central point. I had to drive out the shaft that had a couple of keys in both ends to engage the throttle arms. In the process, one of the copper bushings got damaged and they are not a separate part from the base plate. I went on eBay and found a copper bushing that was 3/8” x 1/2” by 3/4” which is actually the size of the OD and length. The ID was a little bit tight so I drilled out the inside with a drill bit of a close size and it all went back together again. The float bowls and jets were all ultrasound cleaned and the o-rings were replaced from my handy K&L Keihin carb repair kit box.

Again, the float settings for the carburetors were off more than a bit. The last set for my friend's CB350F was much worse, though. 

The next challenge was to install new aftermarket intake manifold rubbers. There are two different part numbers used on 1-4 and 2-3, but they are slightly different shaped and I spent a half hour trying to get the carbs pushed into place, thinking that the little part numbers indicated on the manifold faces were all to go down. Finally, I had to remove them from the head, push them onto the carb spigots, and turn them until the spacing matched the intake port dimensions. In the end, the two left sides were installed with the lettering down and the two right sides were installed with the letters up! The carbs slipped into the manifolds securely and the next job was to install those shiny new 4:4 mufflers, which were worth more than the bike.

I had installed a set of these for a friend, when they were available about 5 years ago, and recall having some problems getting them to fit up to the brackets properly. I started with the left side 1-2 pipes, which are bolted together at the rear along with the interconnection gasket. When I tried to get the flanges and collars to fit up into the cylinder head, they wouldn’t go deep enough to get some threads for the 6mm nuts to tighten them up. I did finally get the #2 pipe into the head with the stock collars, but the #1 was not having it. I dug through a box of misc flanges and collars and came up with 4 that were the right OD but about 1/4” shorter in height. These eventually allow the #1 pipe to be fitted into the cylinder head, along with a fresh exhaust pipe gasket.

Then the problems really began as the rear mount which incorporates the rear footpeg was about a 1/2” off center from where the bolt goes through the footpeg and the exhaust bracket then to the frame mount. I tried to adjust the stud holes that attach the two pipes together but it wasn’t going well. Finally, I loosened the flanges a bit and pulled the rear bracket up so the bolt would go through. Not only was it off in height, it was about a 1/4” outwards leaving a gap to fill in. Eventually, I was able to bolt everything up, but the pipes were in a bit of a bind. I think that they missed the mark on bending the header pipes correctly which caused the misalignment at the rear.

When I looked at the right side pair, before installation, I compared the flanges of the old and new pipes and discovered that the old pipe flange was welded flush with the pipe, leaving a nice 90-degree corner for the collars to push up against them to hold into the cylinder head port. The new ones had thicker flanges that were welded in where the flanges would normally rest, causing them to appear to be too short to install. I used one set of the shorter collars on one pipe and wound up cutting down the stock set about an eighth of an inch to allow for the flange problem.

Again, when the headers were bolted into the exhaust ports, the rear bracket was a little low and about a half inch outwards away from the frame mount. I installed a set of thick washers to take up the space and sourced a longer bolt to finish up the installation. I spent more than 4 hours just trying to fit up the exhaust system and even though they are nice and new and shiny, they really don’t fit the bike properly.

The mufflers had little stickers that were from QC and said “checked” but I am not sure that whatever they checked was accurate. Anyway, they are on the bike. I did start it up on a remote bottle to see how it would run now but there were some lingering carb problems that needed to be addressed before a good test ride is undertaken.

I removed the carbs again and switched the connecting shaft around 180 degrees to get the keyways and shaft machining oriented properly. The damaged bushing left a little bit of extra slop in the system, but they worked much better this time. However, when I put the gauges on them to sync all four, the #3 slide adjustment wouldn’t sync with the other three. I carefully dismantled the #3 carb top and extracted the slide to check for any irregularities, then reset everything once again. Finally, they were all reading the same and the idle smoothed out considerably. If the #3 slide was always higher than the other three, previously, that might explain the overheating of that cylinder and the head gasket failure.

Two things led me to think that the brake shoes and points were all original to the bike at 17k miles. The rear brake rod needed all the adjustment used up to get the rear brake to function properly, which generally means that the shoes are all worn down. For riders who have some fear about heavy use of front brakes, often wear out the rear brakes prematurely because that is their main source of stopping the bike. Imagine my surprise when I removed the brake panel and found the shoes to be at close to 4mm, which is apparently the stock thickness. I had purchased a set of Vesrah aftermarket brake shoes from an eBay seller and they came out of the box at 4mm! So, once installed on the bike, the rod adjustment nut is still mostly threaded all the way up. There is a pedal adjustment to lower the standard height setting, so that will affect the adjustment nut setting, but normally it should be way at the end of the rod when everything is new. Perhaps, the drum is worn out, which seems unlikely.

In adjusting the ignition timing, I had to rotate the backing plate all the way in the adjustment slots in order to retard the ignition timing at idle and it was still going a bit past the full advance marks. Looking at the point gaps, they were down around .008” instead of the normal .012-.016” range, which indicates that the rubbing blocks were all worn down from 17k miles of operation. Normally, the points should be changed about 12k miles, so they are undoubtedly the originals from 1973. I ordered one of the inexpensive Chinese-made electronic ignition plates and that should stabilize the ignition timing.

Apart from replacing the tires and drive chain, all it needs is a really good detail and polish to bring it back to its former glory. I think that the previous, now deceased owner would approve of my handling of his precious CB350 Four.

Bill Silver aka MrHonda



The carbs had to come off again as the linkage bushings were allowing too much play. I bought a used bracket plate from an eBay seller and also re-jetted the mains to #78, up from the stock #75 sizes. This, coupled with the newly installed e-ignition allowed the bike to run smoother with a bit more pep. The carb synch went well and all four are staying equal with each other.

I wound up replacing the fork seals, as they were the originals and weeping a bit. I put the bike into my name and registered it. It gets ridden a few times a week, but the suspension is still rather rough for me. My Sunday ride is a 1991 NT650 Hawk GT and I really enjoy that bike. So, the 350F will go on the market and hopefully to a good home where it can be appreciated for its glory after 50 years.

Friday, November 10, 2023

It’s a DADs bike… 1973 CB350F revisited-Part 1

Part 1.

I have owned a few of these bikes, including one that I bought, brand new, in partnership with my step-dad, Ray. I got out of the USAF in 1971 and had a few odd bikes afterward. Dad got started riding when my Mom bought him a 125cc Wards Riverside 2-stroke single that was on sale for a couple of hundred dollars brand new. He rode it sparingly and then somewhere bought an orange and white CL350 paint shaker Scrambler to ride to work. When the CB350F was released in 1973, we decided that this was the bike for us. The bikes came in sparkly Red and Green paint schemes. We chose the red one.

We shared riding it for a while, then he picked up a green 1976 CB750A. He switched the oil to a synthetic brand and noticed that the bike ran cooler and maybe a little quieter. They are a heavy bike, so after I had bought a new 1978 CX500 and rode it for a few thousand miles, he bought that one from me and enjoyed the low-maintenance ride. But, back to the CB350F.

We wrangled a deal with the local Honda dealer, for something like $1400. They were lighter and smoother than any of the previous bikes we had experienced, but it was kind of slow compared to the CB/CL350 twins of the time. The CL350s were geared a little lower than the CB350s and that just made them shake even worse. Out with the twin and in with the Four!

I borrowed it one weekend and drove it all the way into LA to see my girlfriend who I met before I went into the service in 1967. We kept in touch over the years and she invited me up to visit for the weekend. The freeways were a little tamer back then and I didn’t give much thought to running the bike up 100 miles each way.

After not too long, those cute little four-pipe mufflers started to corrode from the inside, so the “fix” at the time was to saw off the header pipes at the muffler weld joint and install the slip-on 4:2 RamFlow mufflers, which were noisier and probably didn’t do much for the power output. But, they were cheaper than buying a full set of OEM mufflers at the time, so that is what happened.

When the CB400F came out, a quick test ride made the CB350F obsolete immediately, despite the same engine architecture, but the new 6-speed transmission and the 4into1 exhaust system were too seductive to ignore. So, I bought a new CB400F and Dad kept riding the CB350F for a few years.

When I was road racing, back in the 1970s, the AFM club sponsored a 6-hour endurance race at Ontario Motor Speedway. The first one was in 1978. I had been racing 125s, having won the 125 Production Championship on a CB125S1. I had raced the CB400F for a few races, then sold it to my brother who put over 30k miles on it. So, at the time, I didn’t have anything to ride in the 6-hour until I happened upon a running, but somewhat sad CB350F for sale at $500. I still had a Yoshimura R&T camshaft, an electronic ignition that came from my CB400F. I had Rob North roll up a reverse-cone megaphone to fit onto the aftermarket 4into1 exhaust pipe. I added a new pair of Dunlop K70 tires and put it all together just in time to sign up for the race.

It was probably the slowest bike in the entire field, but when the race began, it started to rain! The bike, not having a lot of power and fresh tires stayed on the track without difficulties while others were sliding off under power in the tight turns. Even with all of the speed goodies installed, the bike still wouldn’t go over about 95 mph. It did get about 30+ mpg under race conditions, so we only had to stop for fuel about every 100 miles. Eventually, the track dried out and we carried on, eventually getting a top 10 result in our 350cc class with the slow, but reliable CB350 Four.

I have several friends who currently own CB350F bikes. One bought up one of the $1600 sets of reproduction mufflers from CMSNL about 5-6 years ago when they were available and I installed them on his bike. They really sound lovely, when the mufflers are all intact and certainly look the part of a performance machine.

My other friend picked up a 4-pipe CB350F from Mecum auctions in 2022, but stored it in his storage unit without ever riding it at all. There is a story on my blog page about that bike and its problems with carburetors and an electronic ignition failure.

Truthfully, I have watched the auction prices skyrocket lately on these bikes when they come up with stock pipes, especially. Most of the ones I have seen for sale, locally, were in sad shape with faded paint, cracked or missing side covers, aftermarket exhaust pipes and a round or two of road-rash from crashes in the past. With all I have going on lately; the CM185 Twinstar twins and a CL77 engine rebuild (story coming), I really don’t go hunting for CB350 Fours. Then, Facebook Marketplace posted one that was too good to be true.. or was it?

Seller's Description

1973 Honda 350 Four. Has new battery. Comes with new exhaust pipes still in the box. Starts up and runs but leaks oil. I have to many other projects going on so I don't have the time to spend on it. 

                                                CB350F after the new pipes were installed.

Well, that caught my attention, so I sent a message on Messenger asking if I could set an appointment time to come up and buy the bike. The bike had been listed for 12 hours and I figured that the seller would be swamped with messages and offers to buy it. Perhaps, one of the detractions was that the bike was in Murrieta, CA which is about 75 miles away from me down in Spring Valley. It’s a good 1.5-hour drive each way if you are lucky to miss the afternoon traffic crunch going northward.

To my surprise, the seller replied from work and said that he could meet me at 2pm. I told him that I was coming with cash and a truck and I didn’t have to ask permission from a wife or other significant other. He laughed and said come on up! He even sent photos of the mufflers still in the boxes, to confirm that they were part of the package and not some aftermarket system. Well, I couldn’t get up there quick enough!

The backstory for the bike was it belonged to his Dad, who had passed away recently. Dad had a Mustang Convertible, and a Baja Bug, both of which had been sold, and this shiny red 1973 CB350F left to sell. I had mentioned that I had owned one when they were new, along with my Dad and that made him feel happy that the bike was going to a good home. He did research my name on FB and knew that I knew what I was doing and that I could make it come back to life again.

The bike shows a serious oil leak, seemingly at the head gasket area, which had been drooling down the middle of the engine and onto the bottom of the crash bar. Beyond that, you could see the mufflers blowing out from corrosion, but the gas tank was super clean inside, the paint was like new and the chrome was in really great condition. And yes, there were actual new reproduction mufflers, three of which were still in their original boxes. Included were a couple of old helmets, a mint sales brochure, the owner’s manual in the tool tray, and a new in-the-package 3x5 Honda flag! As an extra bonus, the name Soichiro was applied just below the Honda tank badge.

We completed the transaction, loaded up the truck and I turned around at 2pm for the return leg back to San Diego. It had been spitting rain intermittently but the traffic was not as bad going south as it was for the late commuters going northbound on the I-15. I was very happy to have landed this great bike, even with some leaky bits that will need attention. The title was clear, registration paid to Feb 2024 and I had a good feeling that this bike might be with me for a good while.

Tuesday, November 7, 2023

Early or Late? How do you tell the difference between vintage Hondas?

The terms “early” and “late” are somewhat subjective and somewhat objective, depending on how you are applying the definition. Since American Honda set up shop in 1958, just about everything sold before 1960-61 would be considered “really early,” by most aficionados of the marque. Other than the first generation Honda Cubs, the CB92 and CA95 Benlys, the “big bikes” (250-305cc) were dry-sump Dreams and few of those were sold in the beginning.

"Early" CA77 305cc Dream (AHMC)

Once Honda’s production machinery really ramped up in the early 1960s, bikes came pouring off the lines in as little as every 15 seconds! That figure applies to Honda step-thru Cub models, however. Those early pushrod bikes were run continuously until about 1965, when the OHC engine designs took over. Some versions of the Honda Cub 50s (and some 90cc models) have been in continuous production since 1959, with over 100 million units produced, worldwide.

Other “early” small-bore machines were the OHV Honda 90 street and trail bikes, known as the C200 and the CT200. Again, these were superseded by OHC engines in the 1965 era.

Looking at the small twins, the 150cc Benly Touring 150s, which were also released in 1959, had a styling makeover in 1963, where the fuel tank, panels, rubbers, handlebars and mufflers were all redesigned.

Similarly, the “early” 250-305cc Dreams had their own rework sessions in late 1963, where the model changed from C(CA)77 to C(CA)78, which brought changes to the fuel tank, side panels, rubbers, tank badges, and handlebar hardware. So, the true CA77 models can be considered “early” while the CA78s are recognized as “late” versions. While these styling changes are readily apparent, that was not the end of the design process. Honda reconfigured the frame, tool tray, battery ground, battery, and side covers (and knobs) in 1966, changing the battery size/shape from the early, tall, thin battery to the wider, shorter 12N9-3A unit, also used in the CB77s.

"Late" CA77 Dream 305 

Most collectors think the 1961-64 CB77s, equipped with flat handlebars, steel forks, flat seats and reverse-needle speedometer/tachometers were considered to be the classic “early versions.” In 1965, the flat handlebars gave way to low-rise units and the speedo-tach meter set mirrored the concentric CB450 Black Bomber instruments. 1966 brought alloy forks, requiring a new front fender stay design, plus the upswept seat shape, all of which carried through to the end of production. Those features are commonly referred to as “late CB77” editions.

For many Scrambler owners, the 1962-65 CL72 250cc Scramblers had the look and the sounds associated with “early” models, which included slender alloy fenders, straight exhaust pipes with no muffler can on the back and the mostly ineffective “small brake” wheels/hubs. In 1965, the CL77 was released, initially as a big bore motor transplant for the CL72. 

The fenders were changed to steel and they gradually widened to better encompass the rear wheel debris throw-off and to help keep them from cracking. The 1965 CL72 and CL77s had a “slip-on” muffler, which wrapped around the ends of the twin exhaust pipes, to better reduce the high-pitched, high-decibel exhaust notes. Those were quickly removed by the owners, forcing Honda to weld mufflers onto the later generation of exhaust systems.

By 1966, the CL77s were completely re-engineered with new alloy forks, double-leading shoe brakes, rubber-mounted rear fender, seat, exhaust, footpegs, fork ears, and a thicker chain guard. The net effect was a more beefy profile, carrying more weight and losing the slim, sleek look of the original concept. However, these “later” bikes were far more reliable and had the much-needed braking power lacking in the “early” models.

In 1965, Honda’s engineers refined the 250-305 engines, lowering the compression, changing the fin shape pattern of the cylinder heads, adding “square bowl” carburetors, and other details that held them apart from the “early” editions.

1966 brought wholesale changes to the suspension systems on many models. The “early” S90, CB160, CB77, and CL77 caught up to the CB450K0 Black Bombers by having all of their fork lowers changed from the frame-color steel style to silver-painted alloy forks. The fork style helps delineate the “early” and “late” division lines on all of those models.

In some cases, either the year or the country specification made a distinction between “early” and “late” types of handlebars. In some cases, early model Honda Sport Cubs, Super 90s and CB160s had “low bar” handlebar configurations. As production and sales increased in the US, a determination was made that the US bikes should have “Western” handlebars (read higher and wider) than the domestic and European counterparts. So, the cool little “W” shaped handlebars for the C110 Sport Cubs and Super 90s gave way to unattractive and out-of-proportion “Western” handlebar configurations, requiring whole new cable sets for each model. 

Many of the bikes with “A” (for America) designators, like CA110, CA77 and US-specification CB160s and CB77s all had “Western bar” handlebar/cable combinations. However, if the bikes came into the US before 1964, they often had the lower handlebar sets, found on non-US models. If you are restoring a 1960s model bike, exactly to as-sold specifications, then you will have to study your parts books carefully to establish which handlebars and cables are needed to make the bike correct for that year's edition.

Up to 1968, turn signals were not specified for the US market. The Honda S90 and CL90s and the CB/CL450s were a few of the carry-over machines, that came to the US without turn signals in the beginning and then had them added towards the end of production, which carried on past the 1968 cut-off date. Obviously, the turn signal/no turn signal machines are the dividing line between “early” and “late” models in Honda’s lineup for those affected by the change.

Another aspect of “late/early” models is how the bikes were affected by the change from JIS thread pitch to ISO pitches, starting with the 1968 production models. The 250-305s and 160s were out of production by the end of 1967, so are not necessarily affected. You will find some models, like the “early” CL175K0 Scramblers, which are built with two sets of fasteners, as production progressed into the 1968-beyond models.

Mirror, Mirror on the bar, I see nothing where you are…

Honda Motor Corporation began using small rectangular mirrors on their street bikes all the way back to about 1957 on the C70-71, C75-76, and CE71 Dream Sport models. The product code on those mirrors was 250, which is the first generation 250cc Dream model. When the C92-95 Benly 125-150cc models were released, the mirror part number had a 200 code part, attributed to the Benly series machines. Honda used the 200 series mirrors on just about every 250-305cc model, plus the 125-150cc Benlys from 1959 through the 1967 production run. Because there were so many machines out in service during the 1960s, Honda continued to make the mirrors available due to demand.

Somewhere along the line, someone, for some reason, chose to supersede the 200 series mirrors to product code 041, which is for a C50 step-thru model. Obviously, the handlebar location of a 50cc step-thru is way different than that of a 250-305cc street machine. The mirror head angle on the 200 mirrors is about 15 degrees above horizontal, whereas the 041 code mirrors are a solid 45 degrees upwards. When 041 mirrors are mounted on a larger street bike, the mirror angle cannot be adjusted to be useful for the large bike rider. All you see is sky/clouds, no matter how you adjust the lever brackets on the handlebars. The only true solution is to bend the mirror heads downwards until they allow for normal viewing angles.

The mirrors all have 8mm threaded stems, which are the same diameter as the mirror stalks. This is a fairly stout chrome-plated steel rod, so they are not easily manipulated. What is required is a hefty, solid-mounted workbench vise and an appropriately large Crescent wrench (18” in this case) to make the adjustments.

If you have another person available to hold the mirror stem, keeping the lever bracket locked in place, you may be able to do this on the bike. I don’t recommend it, however. It only takes a few moments to unscrew the mirror from the bracket and secure it in a vise, once you have removed the long locking nut.

Once you have given it a good twist, check the head angle and if it is close to what you see in the photos, you should be all set to go riding with the security that you will be able to see the traffic behind you in your OEM Honda mirrors.

Thus far, the mirrors are still available from Honda warehouses, across the country and around the world. 88110-041-000 is the part number for the right mirror and 88120-041-811 will get you the left side unit.

 Bill “MrHonda” Silver  


Originally offered 01/2019 on the site (now defunct)