Wednesday, January 29, 2025

MrHonda gets strafed by a Black Bomber


What goes around sometimes comes back to me. I had a history with this CB450K0 Black Bomber dating back in 2022, when the then-owner brought it to me to get running after it sat for years. Something came loose inside the generator and damaged the stator and rotor. The carbs were all gummy, the spark advancer springs were loose, the battery was dead and the oil pump mod needed to be done. I got it running well, but the later reports were that one of the carb bowl gaskets was leaking. I stopped by to have a look at it about a year ago and asked them to order a new gasket and I would re-install it.


No word until this week 1/15/2024, when the new owner, who was the housemate of the original owner called to ask me how much these bikes were worth. He was suffering the aftereffects of some kind of accident (not on the bike) and needed hip surgery. He was out of work so needed some ready cash ASAP. He offered the bike at a below-market price, considering what was going to be needed again to get the bike up and running, so I bought it, picked it up and brought it home for a re-acquaintance review.

The Motobatt battery, which was $91 in 2022 had 5 volts remaining. The gasoline was stinky and somewhat tainted by the RedCote sealer that had been installed previously. I removed the air filters, battery and carburetors for some cleaning and getting it ready for coming back to life again.

When I opened up the carbs, one already had a sinking float, so that probably was adding to the leaking float bowl gasket problem. The old gas hadn’t congealed too badly and they came out clean after a visit to the ultrasonic cleaner. I had tried to drain the fuel tank through one of the petcock fittings with a long hose attached, but nothing came out in the Reserve position. Silly me, with the tank half off the bike, decided to unscrew the petcock from the tank, and out came a gallon of stinky old gasoline all over me and the bike.


The petcock feed holes were all blocked up, due to disintegration of the 4-hole gasket, the little nylon filter on the reserve fitting was ripped open and the main brass fuel tube had split down the middle. So, a replacement petcock and some carb floats were ordered from 4into.com which were shipped out the next day. In the meantime, I decided to try to repair the float using a heat gun to heat up the gasoline inside enough to show me where the pinhole leak was located. Apparently, the floats were aftermarket parts and the solder joint was not completely fuel-proof. I heated the float up with a heat gun, but suddenly it went POP and separated on the bench. You could see the high water mark inside the float lobe cavity where gasoline had made an ingress inside the part. I fiddled with it for a half hour, cleaning the solder off the edges of the two halves, and tried to re-solder the pieces together. It got kind of covered with lead blobs, so probably weighs a bit more than the other site. While waiting for the new parts, I thought that maybe the repairs would be good enough to get the bike up and running again.

The bike came with 4 sets of OEM carb repair kits, a new camchain with a master link, A brand new factory wiring harness, the owner’s manual, a photocopy of the parts and service manual and a set of brand new OEM tank badges! Sometimes you just get lucky.

With the temporarily-repaired float installed, I tried to fire up the bike, but the starter clutch was skipping badly. I removed the left covers and pulled the rotor out, only to find that one of the roller spring caps was jammed into the starter clutch spring holes. I had to remove the starter clutch to pull out the spring and cap. I had a set of the standard springs for the 250-305s and installed fresh ones after checking that the caps wouldn’t get caught up again. With the spark plugs out, the starter clutch seemed to work fine, but after it was all back together again, the clutch would skip intermittently. 

The rotor was marked K5 and there seemed to be some part number changes for the Bombers, but more importantly, the springs had a 283 code part number instead of the 253 springs. I rush-ordered the correct springs. In the meantime, I determined that the carb jetting was incorrect, with #130 main jets and #38 idle jets installed instead of the specified #125 and #35 jet sets. I was able to get #125 main jets from 4into1.com but the idle jets seemed to be NLA almost everywhere. I did find some listed at cmsnl.com but they were on some kind of back-order and not available until early Feb. I did receive new floats and the #125 mains, so swapped out all those parts and the bike started up fairly quickly and I was able to run it around the block.


The first test ride was initially a bit troubling, as the bike seemed to jump when I went around the corner. I thought it had a flat tire or something odd, but what turned out to be the cause was that the steering head bearings were notched and the handlebars self-centered when you moved them left of right. I happened to have a set of tapered steering head bearings on hand, so spent a couple of hours taking all of the handlebars and headlight ears, etc loose, then driving out the old races and driving in the new ones on a bike that was sitting on the centerstand and a small floor jack beneath the forward frame rail junction.


The 283 springs arrived just before I was going to the Mecum auctions in Las Vegas, so I hurriedly checked them out for installation. They were slightly shorter than the 253 springs, but visibly thicker wire gauge. I popped them in and installed the rotor back onto the crankshaft. This time, the spark plugs were still installed and the starter clutch seemed to be pulling the motor over okay. I had checked the compression and both cylinders were showing 175 psi so the starter clutch had its work cut out for it.

After putting all of the covers and bits back together, the starter clutch was pulling the engine over markedly better, but still had a few skips every once in awhile. I noticed that the rotor went onto the starter clutch hub very easily and now wonder if there is a different dimension in the clutch hub.

There were some issues with the speedometer light bulbs being either blown out or in the wrong locations, so that needed some attention. The dimmer switch contacts are a bit corroded, so that switching from Lo to Hi beams is a bit inconsistent. Apart from that, it is pretty much ready to find a new home with a Bomber fan, somewhere.


Bill Silver

aka MrHonda

www.vintagehonda.com

Sunday, January 19, 2025

MrHonda’s little shop of horrors….

Factory photo courtesy AHMC  

It started last November, pushing out a CL77, then taking in a CB750 which had been treated to an 836cc kit, but someone forgot to get one of the wrist pin clips all the way in and it ground a groove in one liner. In the background, I was piecing an early CL77 together from misc bits (separate story coming).


Then, there was the return of the blue CL175K3 that caused a lot of headaches in the beginning, then has come back for a mysterious oil leak and poor running conditions. No mechanic wants to have comebacks return the shop, but this came back with intractable problems with the suspension and carburetion.


I had a 1963 CB77 dropped into my lap which had a reported replacement top end due to piston seizures but was never run after re-assembly. That one required pulling the engine again, as the shift drum had rusted the forks in place, due to inactivity for many generations. That one was a pretty nice original bike but needed the usual tires, cables, battery, carb overhaul, tank sealing and various electrical repairs. Thankfully, that one sold to a local enthusiast.


The CB750 had a removable frame section above the engine so I could remove the top end without pulling the 175 lb engine assembly from the frame. The bike was spewing oil out of the #3 cylinder as well as a big leak at the crankshaft seal behind the ignition system. The cylinders had to be shipped to Cycle-Xpress in Wisconsin for liner replacement and boring, plus fitting new pistons to the rest of the cylinders. Slowly it came back together but then the carburetors wouldn’t fit back onto the cylinder head spigots. The chassis was late 1969-early 1970 and the carbs were 1975. After trying to force the carb rack back on with new copies of the manifolds that were on the bike, I discovered that Honda made revised manifolds for 1971-76 bikes. They solved the problem at a cost of $150 for the set.


                                                            Factory photo courtesy AHMC


A KIA camshaft seal has the same dimensions as the OEM crankshaft seal on the 750, but without the ridge that normally holds the seal in the cases. I pried the old one out and installed the new one from the outside. Otherwise, you have to split the cases to install the OEM seal where it registers with a groove in the upper and lower case halves.


There were more problems with just changing the oil and filter. The drain plug washer was missing and the old oil was diluted by some kind of miracle engine fluid that the owner thought might fix the oil pumping out the pipe. The oil filter was missing the flat washer that sits on top of the spring that pushes against the oil filter element. The exhaust system was a fabrication set that had two pipes anchored to the footpeg bolts, but the inner pipes were held to the bike and outer pipes with hose clamps! Then the battery died and I had to push it 6 blocks back home again. It’s just one thing after another, it seems.


The CL77 bike came with the wrong rear wheel and swing arm and missing lots of parts. The old tire on the replacement wheel was a monster 4.00x19 rock hard chunk of rubber. I was able to eventually pry it off and spoon on a new one, but when I fitted the wheel to the bike the wheel locked up when I tightened up the axle nut. I had missed the fact that someone had robbed the hub of the inner wheel bearing and the spacer. I rebuilt the engine, which came with a CB77 cylinder head/tach drive and then discovered that the crankshaft was also from a CB with the oil hole for the starter clutch. There were damaged gears and it needed the full transmission overhaul with replacement bushings. Eventually, it came back to life and sounded pretty good, but still looked a bit tatty.


The CL77 clutch was dismantled during engine repairs and inspected with all parts apparently correct for the engine, but the clutch pull was a 2-handed affair, so was inspected once again and some softer springs fitted, which fixed that issue. There were many problems with the chassis wiring, including a dead headlight bulb and then the tail light needed to be replaced with a different bracket. The fender was painted but not cleared for a good ground path, so more work was needed to remedy that. Finding a front fender for CL72-77s became quite challenging during the process.


The CL175 was reported to have a little oil leak, but the owner had cleaned it off before it came back to me. I had to guess where it might be and reseal the left side cylinder head cover. This bike had been running some aftermarket carburetors as the original ones were fitted with some aftermarket parts that prevented the bike from running properly. The left side was the biggest headache, despite having the carburetors off numerous times for cleaning and inspection. Eventually, I checked the #90 main jets on both carbs and the left side and finally determined that someone had drilled out the jet to about a #105 size, which caused all of the plug fouling. Fitting a proper sized main jet finally fixed that issue.


                                                        Factory photo courtesy AHMC


Then, there was a problem with the front end. When the forks were removed to allow the new headlight ears to be fitted, a bit of slack was noticed at the bottom of the forks, as if the fork springs were too short. I pulled the right side off and wound up fitting a ground down intake valve spring into a short spacer to put pre-load on the fork assembly. The bike had suffered some kind of crash damage that caused the forks to be out of alignment, making refitting of the fork legs difficult. On top of that, the front brake started to cause the front wheel to dive to the right under braking. Inspection showed that the primary shoe was contacting the drum fully, but the secondary shoe was not. The brake plate was checked and the shoes cleaned and synchronized again, but nothing influenced the brake to behave normally. Finally, the bike was sent to a frame shop to check out the frame alignment and perhaps replace the steering stem.


The battery wasn’t charging properly, so the engine continued to run roughly. The OEM style rectifier was replaced with a solid-state unit, which seemed to improve the battery stability and thus the coils were getting 12v on a regular basis. Then, there was a problem with the replacement gas caps not venting properly and the petcock not feeding the carburetors equally.


Diagnosing and repairing these continuing problems takes at toll on your psyche. When you have worked on Honda products for 50 years, but suddenly everything you attempt seems to fail due to some mysterious maladies that are hiding in the background, you begin to doubt your sanity or ability. Obviously, problems such as these eventually have a resolution, sometimes requiring replacement of what seem to be good parts and doing a lot of questioning your mind about what is missing to cure the problem.


At sometime, I will hang up my wrenches, but even though I am 76 years old, my overall health is good, so I will continue to try to sift through the clues and come up with some resolutions that bring the bikes back to something close to what they had experienced after driving off the showroom floor.


It would be great to have an intern or understudy to absorb the experience and information that I have floating around in my head. I have spent many hours helping on various Facebook forums for various models, as well as continuing to supply my restoration guide downloads for the 250-305 series models. Hopefully, what I have shared is taken in as fact in most cases to those who are generations behind me and share with their peers and any upcoming enthusiasts to take the knowledge forward into the future.



Bill Silver aka MrHonda

www.vintagehonda.com 01/19/2025

Tuesday, October 15, 2024

It’s all in your head… 250-305 cylinder heads.

For mass manufacturing, simplifying the production process yields more products at a cheaper unit price. As Honda ramped up production from the early days of J-Benly, SA/SB-ME-MF singles, their goal was to build a reliable and punchy OHC twin, which was indeed inaugurated in 1957. Honda designers must have decided that making thousands of little valve seats for the cylinder heads could be replaced by a cast-iron cylinder head “skull” which incorporated the combustion chamber, including valve seats along with the spark plug hole. The cast-iron skull was then set into another mold in which was poured molten aluminum, fusing the two dis-similar metals together into a single unit. From there, valve seats could be easily cut and the combustion chamber either left in the 250cc-sized hemispherical shape or the edges were chamfered out to match the step up from the 54mm 250 piston size to 60mm enlargement for the 305cc displacement.


As brilliant as the design was for manufacturing, the heads did have a tendency to have the skulls work loose from the alloy castings, causing oil leaks around the edges of the spark plug holes.


This discussion will revolve around the “wet-sump” 250-305 engines which began production in 1960 and carried on until 1967. The earlier dry-sump engines are in a different class of design and application and are seldom seen in the US. When Honda came to the US in 1959, they offered the CE71 and some various 250-305cc versions of the dry-sump (separate oil tank supply) bikes, but swiftly moved into the newly-designed wet-sump types.


The 250-305 Dreams were introduced in 1960 in the new wet-sump format, followed by the CB72-77 Super Sports in 1961. The range was extended in 1962 with the newly designed CL72 250cc Scrambler.


For the first two years, the cylinder heads were offered with tiny 10mm spark plug holes. In early 1962, the heads were machined for the commonly seen 12mm (NGK D8HA spark plugs) and that continued throughout the rest of the production runs for all models.


Visually, the early heads were most easily identified by the U-shaped machine work done between the exhaust ports on the cylinder head fins. In 1965, there were numerous detail changes to the engines, including the elimination of the machining step for the fins, as they were now cast in a clean V-shaped design.

                                                                1965-on V-pattern head


1960-64 U-fin cylinder head.


People often question about the interchangeability of the cylinder heads across the three models. To manage the number of parts needed to build these engines, all the cylinder head castings are the same to allow for cross-building of the various engines. Apart from the single intake port Dream heads, all the dual port heads will interchange between Scramblers and Super Hawk models. Early Dreams had smaller exhaust valves, which were upgraded to the CB series exhausts in 1962. For 250-305 dual port heads, they all share the same valves, despite the difference in displacement sizes. There is a slight difference in the intake port size for the 250 heads, where the 22mm carburetor insulators match up to the intake ports.


Honda was able to use the same castings for the dual port heads, as far as the combustion chambers are concerned. The 54mm bore size of a 250, requires a tight hemispherical combustion chamber with a small squish area at the edge of the piston crowns. The same castings used for the 60mm 305 engines require a beveled chamfered machine cut to allow for the fitting of the larger pistons.



                                                      Combustion chamber for the 250cc engines



                                                          305cc combustion chamber

These cylinder heads do not use valve stem seals, rather there was a thin air passage drilled into the head that matched up with some cross-drilled intake valve guides. This system was thought to break up the oil film on the intake valve stems, reducing the tendency to suck engine oil past the stems and guides into the combustion chambers. Remarkably, this system seems to have worked efficiently for all the years, until 1967. Honda decided to eliminate the whole system just in the last year. The last generation engines don’t seem to be more prone to using oil than the previous types, however.


So, in conclusion, the main difference between 250 and 305 cylinder heads is the machine work on the edges of the combustion chambers. Heads are generally interchangeable between the various versions of the engines. Considering the engineering challenges faced in the late 1950s, to build motorcycle engines that could rev up to 9k plus in a world of plodding, low-rev OHV designs from European/British companies, the speed of manufacturing of components led to the dominance of Honda in the world of motorcycle manufacturing.


Bill Silver

aka MrHonda

www.vintagehonda.com

10-2024

Friday, September 20, 2024

MrHonda dodges a scammer…

What started out with an SD Reader ad for my former Pink Panther CB77 Honda (now restored to Silver and Scarlet Red) culminated in an attempt to scam me out of at least $980. The SD Reader ad had my phone number, so when I got a text message from someone wanting to buy the bike, I was not too concerned. In fact, I texted him a photo of the “Hot Rod CB77” bike that is also for sale and he said he would buy it for $300 less than my asking price. It appeared that I was going to cash in on a double sale and put some cash in the bank, but in the end, it was just a scam.



Initially, the man messaged me that his “PA” had made a mistake and added an additional $1500 to the amount, which was supposed to go to the shipper. He asked me to give those funds to the shipper when they arrived to pick up the bike. I agreed, as long as funds were secured in the bank.


A couple of days later, a check arrived with the name of a construction company. To that point, this man had never introduced himself, so I had to ask his name. Finally, I did a search on the business name on the envelope and found just one name in Virginia where the envelope was sent from. The man said he was working in Georgia, which is why his phone number had an Atlanta area code.


I took the business check to the bank and asked if they could verify the funds. Apparently that is not easily done, so I was told that if it was deposited into the system, there would be some indicators as to whether the check would go through or not. The check was deposited and initially there was just a couple hundred dollar release from the $11,800 business check I received.


I became suspicious looking at the check, which had a different business name from a corporation in NY. The bank it was drawn on was in Illinois. So, I was looking at a guy who was currently in GA, but living in VA, with a bank account in IL and a master account in NY. It didn’t really sit right with me, but I was willing to let it play out until the check cleared.


After 2 days, there was a partial release of $5k. I asked the bank if this was a good sign or not, but was advised to let the check go all the way through to verify the funds.


The next day, I started getting text messages asking if I had various ways of transferring funds, like Venmo or PayPal. I only use PayPal but the current balance was zero. Then, he said that he had promised his shipping partner friend a $980 amount for some kind of services and could I send that “right away.” This was beginning to sound like a classic Nigerian 419 scam. Finally, I was asked if I could send a postal money order to his friend that day. I was on the road to my chiropractor appointment which is an 80-mile round trip. I turned off my phone and went to my appointment and headed back home again.


When I turned the phone back on, there was another message asking if I was going to make this payment to his friend. He had never offered the name of his friend or how to contact him with funds, but I sensed that the game was up after that message. I told him that I was waiting for the check to clear completely and then the messages went quiet.


The next morning, I was greeted by multiple messages from my bank saying that I was overdrawn in my account with a negative $2k balance. The “item had been returned” so the $11,800 amount was not valid, plus the hold on my account was reversing my balance from plus $4k to a minus $2k. I was advised to “fix the problem” ASAP or an overdraft charge of $36 was to be charged and it would certainly affect my credit score.

That morning, my friend Bill had driven down from Orange County to help me finish putting his SL100 project back together. I figured that I had plenty of time to finish the bike and then get to the bank to sort things out. Well, of course, the bike took 7 hours (including lunch) and the time was getting short to get to the bank.


In the interim I received another flurry of emails from the bank, stating that the overdraft charge was reversed and my account was back to $4k again. I don’t know if this was an automatic system re-balancing or if someone got directly involved at my branch. Anyway, everything was restored and no further action was required.


When I texted back to the man, telling him that it was a scam, as I was beginning to suspect, he denied it and said I was lying. I copied the bank statement section of my account and texted the line that said “$11.800 item returned.” Then I told him that I was filing a scam report to the BBB, which I did and sent him a copy from the BBB system recognizing the report. Then, I blocked his phone number.


I’m sharing this with you all, as there is a proliferation of scam attempts in the Facebook forums and with increasing spam messages to my email addresses. Do NOT send funds or accept fake checks, no matter how good they look unless they clear the bank completely. Do NOT advance any of your funds to the buyer before the check clears.


The internet is turning into a Wild West show where anything goes now, in the name of financial gain at the expense of the unsuspecting public. With huge data breaches revealing email addresses, phone numbers, account numbers and social security numbers, everyone needs to be on high alert for those people who want to make a buck or a thousand at your expense.


I am musing whether to add this man’s name to the story at the moment. If you want to know who it is, contact me directly.


Be careful out there, folks….


BTW: the bikes are still for sale...


Bill Silver

aka MrHonda

www.vintagehonda.com




Sunday, September 8, 2024

All coiled up, but unable to strike…

With the decreasing availability of OEM Honda (and other makes/models) ignition coils, the only alternative appears to be the Chinese-made copies of single—and dual-output ignition coils that flood the eBay market listings.


I recently had an exchange with one eBay seller about this listing:

High Voltage 12V Ignition Coil For Honda CS90 CL125S CL100S S90 SL90 XL100

I pointed out that none of these models use a 12v coil, but the replies were vague and unhelpful.


This listing: 

6 Volt 1 Ohm Ignition Coil Dual Spark Plug Output for Honda And Others 24-72454 shows the application chart including CB92, CA95, CA160, and CM400T! I doubt that it will last more than a few minutes, as a 1-ohm coil is designed for electronic ignitions.

Case in point:

Recently, my friend Steve P. was finishing up his wonderful restoration of a 1961 Honda CB92 and Hs purchased an aftermarket coil from an eBay seller. After re-checking the cam timing, ignition timing, carburetor jets and metering circuits, he was unable to get the bike to fire up at all. I made the usual suggestions about the basics, which he checked out thoroughly, but still no joy when he hit the starter button, even with some starter fluid sprayed into the intake.


I agreed to come by his place and check his work and the bike over, looking for any concrete reasons why his restored engine and bike were stubbornly inert. The compression tested out to about 100 psi, equally on both sides. We verified that the cam timing and valve lash settings were all correct. The point gap was .014” and they were opening at the F mark.


With the spark plugs still out after the compression test, we grounded the plugs for a spark check. Initially, there seemed to be a strong spark, but in repeated cranking the spark became erratic and finally pretty much quit altogether. One thing that can upset spark creation is a failed or disconnected condense. But when it has a problem, the points will arc heavily during cranking or engine operation attempts. This was not occurring in this instance.


Having checked and eliminated the main possible culprits and noting the diminishing spark output, I pulled the coil primary leads off for an ohms test. The ohms test for the supposed 6v dual-output coil read out at 4.5 ohms. That is a reading expected of most vintage Honda coils that are of the 12v variety, but not for 6v types. When we checked his removed OEM coil, it tested out at about 1.5-1.8 ohms, which is what you would expect from a 6v ignition coil.


                                                        A genuine CB92 ignition coil. 


So, what was happening is that the 12v coil, being fed a diminishing 6-volt supply, was dropping lower with each electric starter test cycle until the voltage dropped below the cut-off limit. The higher resistance of the aftermarket coil curtailed the spark output on a steady decline until it ceased.


It’s easy to see an initial spark at the spark plug on a quick check and assume that it should be enough to run the engine. In observing the decline in spark activity through prolonged engine cranking, you get a truer picture of what is happening. This is a vital clue to troubleshooting an ignition system issue.


In an earlier blog story, back a few years, I wrote about buying a CR93 street bike tribute bike, based on a CB160 chassis with a 5-speed CL175 engine installed. Ironically, I had owned the bike and sold it at a swap meet event in N. Cal. The tank and seat were actual CR93 components fitted to the CB160 chassis. I could see that a great deal of detail work and restoration work had been done to the bike, during its surprise, last minute entry at the Las Vegas Auction. I felt compelled to buy it back and did actually win the auction in the end. https://www.mrhonda.guru/2017/03/the-beast-within-beauty-cr93-replica.html for the story.


The bike had not run recently, so I went through a basic check to see how the basics were doing before trying to start it up. The carbs were cleaned and one float was found to be sinking. Once the carburetion was dialed-in and ignition timing checked, the bike fired up quickly on a fresh battery, but it wouldn’t run more than a few blocks before it began to misfire and finally quit altogether. Backtracking over my previous work and rechecking all the obvious causes, I finally realized that the spark to the plugs was becoming erratic, after just a few minutes of operation.


The CB160/175 series of bikes are all equipped with 12v charging and ignition systems. Finally, I noted that the ignition coil was an aftermarket copy and checked the primary resistance. It was about 1.8 ohms, which is something that you would see for a 6v ignition system or in some cases bikes equipped with electronic ignition systems. Most full electronic ignition systems use coils in the .3 to 1.5 ohm range. When these coils are substituted on a 12v system using points and condenser, the high current draw will burn out the primary coil windings pretty quickly.


Sure enough, when I replaced the coil with one of the 4 ohms range, the bike started immediately and continued to run for an extended period of time without any mis-firings or performance issues. Recently, a customer bike came in with perfomance problems and on a single-cylinder vintage Honda machine and when the coil was checked, it too, had a 4-ohm coil instead of something in that 1.5-1.8 ohm range.


In looking at some of the various eBay listings for aftermarket coils, few, if any, have ohm specifications listed. Because motorcycle coils come in just a few sizes and mounting dimensions, it seems that the sellers are pushing out products that are inappropriate for the desired applications. Typically, you will see the same photos of the same coils listed by various named eBay vendors who are either all working together or all getting the same products from a few manufacturers in China.


Asking questions about the specifications is often a fruitless endeavor, as they are not tech-savvy vendors. They seem to take your questions and then refer to the suppliers in China. I imagine that there are translation difficulities all around, which make finding out the details of a component difficult or impossible.


So, all I can say is BEWARE of aftermarket products, especially in the category of ignition coils. DO NOT buy from one who is unable to supply the correct ohms specifications for their products. Their cheap pricing is enticing, however you may well find yourself scratching your head for hours wondering why the bike won’t run even though you have changed the whole ignition system.


This one small detail makes all the difference in success or frustration when trouble-shooting the cause of engine performance failures. Once Steve replaces his coil with one of the correct primary winding impedance (or puts the original one back in place), the bike should fire up properly and he’ll be a happy man. I feel that this is an important issue that needs to be remembered in times of frustration and confusion after a bike build or repair.



Bill Silver

aka MrHonda

www.vintagehonda.com

Thursday, August 29, 2024

There’s always a reason… find it! CL175 2.0 to completion.

Welcome to MrHonda’s mystery hour, where we delve into the unexplained behaviors of vintage Honda motorcycles, after normal repairs have been completed. In this edition, the subject in question is a 1969 Honda CL175K3, which had an engine overhaul and carburetor cleaning. The engine starts up easily but then loads up the spark plugs quickly with excess fuel.



Spark plug fouling at idle is generally attributed to either the wrong-sized pilot jets, high float levels, blocked air bleed passages at the carburetor inlet ports, incorrect ignition timing, high resistance spark plug caps, defective spark plugs (fake reproductions), low spark voltage due to failing coils, weak condenser, incorrect cam timing or aftermarket parts which are not made to OEM specifications.


Background information: The engine was brought to me in pieces for a rebuild, including the replacement of the kickstarter shaft. The cylinders were still on STD bore sizes, so the bores were honed and new rings were installed. The original valves were re-seated and all new seals and gaskets installed. It was pretty much a standard engine rebuild.


Once installed, the engine was started up, sounding rough as if it was running very rich at idle and just off-idle. It fuel-fouled the spark plugs in just a matter of minutes. The carburetors had been disassembled and cleaned, noting that one of the slide needles were marked D2, which indicates that they are from Keyster carb kit. The idle jets were also from the kit and marked #38, which is correct for this engine series. The main jets were marked #92, which is stock, but I have had issues with the accuracy of the kit parts in many cases. The bike is a Scrambler, with left-side high pipes, which have to be removed or at least loosened up so that the left-side cover, air filter and carburetor can be removed for service. The carburetors were inspected several times after each start-up with no favorable response to any adjustments done to the needle height or float levels. There was an odd situation where the left side carburetor fuel levels were greater than the right side, despite careful float adjustments. The petcock was checked as it was dripping, even in the OFF position.


The petcock had been installed without a sealing washer for the attachment screw that holds the petcock to the bottom of the tank. Additionally, the back side of the fuel lever was uneven allowing fuel to pass the barriers of the 4-hole petcock gasket. Once the fuel lever was flattened out and a sealing washer installed, the petcock functioned normally. Both fuel lines were matched in length to alleviate any issues with fuel flow to each carburetor.


Having removed, cleaned and inspected the OEM carburetors three or four times, I had to start looking at other associated problems that might have been overlooked or assembled in error. Starting with the basics, the compression readings were about 140 psi, which is a bit lower than Honda’s spec for a normal engine. Low compression readings, when both sides are the same, can be indications of incorrect cam timing. This engine had new rings, which were not seated yet, so some leakage was to be expected. A leak-down test showed nothing abnormal, apart from some air leaking into the crankcase past the new rings.


All indications were that the cam timing was correct, although Honda’s tune up book showed the intake valve opening at 10 degrees before top dead center, and actual valve opening appeared to be starting at about 20 degrees. This might look like the cam timing was incorrectly set, however most cam timing readings are taken at .040” so with that in mind the cam timing was correct. I actually removed the top cylinder head cover to verify that the marks were correct, which they were. So, take that off the list of possibilities.


I observed that the aftermarket replacement ignition points were contacting at the very edge of the contact faces, rather than in a more central location. A bit of bending of the stationary contact brought the contact back towards the middle. The gap was rechecked and timing adjusted to suit. The spark advance was checked for proper function in advance and full retard positions. The ignition coil was an aftermarket replacement with the original spark plug caps installed. The caps were measuring about 10k ohms, instead of the preferred 5k ohms, so were replaced. So far, no “smoking gun” was found to cause the rich running of what appeared to be stock OEM or replacement parts.




A set of aftermarket, Chinese-made carburetors had been brought down originally, so in desperation, they were installed. These replacement parts had their own issues. The “set” was actually two right-side carburetor bodies, so that both had the carb adjustment screws on the right side and fuel feed fittings on the left side. Both carbs had the same slides with the same cutaways, as that is what a right-side carburetor would be equipped with.




The carburetors were fitted to the stock intake manifolds which had been flattened off with my little belt sander to ensure flat contact surfaces. Once fitted, the bike was started up and immediately ran cleaner and idled down comfortably without the rich running that was occurring with the “stock” carburetors. At this point I was truly baffled about why the stock carbs failed to function properly, and a set of Chinese carburetors, which had no markings on any of the jets, were working normally.


However, the Chinese carburetors had a different issue. The next day, the bike was hard starting and only ran on almost full choke. As it warmed up, I slowly lowered the choke lever until it would start to stall out again, which indicated that the needles needed to be raised up a bit. The right side needle was a 5 notch type with the clip all the way at the top.. so super lean. I moved the clip to the middle groove. The left side needle came out and was a completely different type with only 3 notches! I went for the full rich option and restarted the engine again. Like magic, the bike took throttle, off idle, and was smooth and responsive in a 5-minute test ride.


I reported this limited success to the owner of the bike project, but could not give a cause for what had happened… until I went to put the old carbs into a box for storage.

Looking carefully at the carb needles, I finally realized that they were of different material. One was a brass D2 Keyster needle, but the other silver-colored needle was not marked at all. Comparing the two, the profiles of the needle tapers were different, as measured with a caliper. Ah, ha! Maybe I was on to something important, after all. Then, I flipped over both of the carb slides, which appeared to be the same, as far as the material and coating was concerned, but then was shocked to see that one slide was an OEM Honda part and the other one was not marked at all! Sitting them side-by-side, I could see that the slide cutaways were a bit different and then looking even more closely, the whole slide bottom, where the needles are located were at a different height! The aftermarket slide was a completely different part, as far as dimensions go for the needle and the cutaway. Eureka, I found it!



I was able to track down a set of OEM needles from an eBay seller, then went to cmsnl.com for the other needle, plus a new OEM slide, plus a pair of OEM idle jets. I now have confidence that with the correct OEM parts installed, the stock OEM carburetors should work normally, as designed. It’s been an arduous task with many hours of removing, inspecting, cleaning and installing the stock carbs over and over again, expecting a better result. I think that has been described as “insanity,” isn’t it?


I thought that this was the end of the story, however the bike had other ideas. When the fueling issue seemed to be solved, a long downhill run, a part of my testing process ended when the bike slowed down for a corner and then went completely DEAD! It had blown a 20 amp fuse. I had no other fuses with the bike and I was stuck a mile away on an uphill return. I called a couple of neighbors and neighbor Paul picked up the phone during his grocery shopping and said he would come and pick me up shortly.


I pushed the bike up an angled cement corner, made for wheelchair access, and left it under the shade of a palm tree. Paul came by, picked me up and dropped me at home. I loaded up the Tacoma and headed back down the hill to where the bike awaited my return. Loading a 280 lb. bike, even with my long ramp into the Tacoma can be challenging, but when I arrived at the bike a somewhat scruffy man was sitting next to it, accompanied by his dog. We spoke about the bike and what had happened. I could tell that he was looking for signs that this was my bike and I was the rightful recipient of it. He happily helped me load the bike into the bed of the Tacoma and walked back to his waiting Honda Accord, with the dog in tow. How amazing that someone came out of nowhere to help out just when I needed it the most!


I unloaded the bike and set to work finding the cause of the short. The bike only has one fuse, so when it is blown you are completely inoperable. I have a resetable relay connected to a set of wires with clips on the end. You can put them on the ends of the fuse holder and it will click on and off, when a short is present. Of course, it seemed perfectly fine all of a sudden. I did track down some worn wire for the rear brake light, which was repaired. Also, the fuse, in the fuse holder, should have been a short 15A fuse, but was a longer 20A fuse. The length of the fuse, caused the ends of the wires that attach to the fuse holder to extend out beyond the plastic fuse holder. That made them vulnerable to contacting a grounded frame area and create a dead short. I put a shorter fuse in the holder and pushed the wire ends into the plastic holder out of harm’s way. Nothing else was evident, so I turned my attention back to the carburetors.


On the next short run, partially down the hill, the bike ran well for about a minute, then went off on one cylinder. I slipped the clutch and revved the engine sky-high to try to get it back home again, just a quarter mile away. After it sat for a moment, it suddenly caught on again and I nursed it back home again. The problem was that the right side carburetor was running out of fuel, while the left side was doing fine. I rechecked the float level with the carb still installed and looked for any signs that perhaps the float was somehow contacting something inside and shutting off the fuel flow. I did another around-the-block test and it started to run on one cylinder again. No matter what I did, it wouldn’t keep fuel in the right carb bowl.


I had already bought another aftermarket petcock, in case there were problems related to the one that came with the bike. I drained the tank and removed the petcock. On more careful inspection I noticed that the two holes that feed the fuel lines to the carburetors were not on the same level. Wow! Could this be a factor in the fuel feed issue? The new petcock had a little screen on the reserve port whereas the original did not. Grasping at straws, I installed the petcock and hooked everything back up. Again, the fuel wouldn’t flow into the carb unless the bowl was dropped down and the float allowed to open the float valve.  The replacement petcock had its own problems. The space where the attachment screw is narrowed more than stock so the proper screw gasket (not included with the petcock) doesn't fit! I had to slowly grind down the OD of the gasket so it would fit snugly down and seal the screw head.




A friend suggested that I try another float bowl. The OEM carb bowls fit right up to the Chinese copies, but the result was the same. I removed the air filter and the carb from the studs to have another look at the bowl venting system and rechecked the float level with the carb held on the side, with just the weight of the plastic floats touching the needle. The measurement was different in that angle, so was re-adjusted again to 21mm.




Comparing the float bowls, I noticed that the brass overflow tube on the aftermarket carburetor had a really tiny hole. The carb had flooded over previously, so I knew that the passage was opened. But when I compared the OEM bowl to the A/M version, the original brass tube had about a 1.5mm hole vs about half of that on the copy. I opened the tip of the tube up with my 1.5mm drill bit and put it all back together once again. I turned on the petcock, waited a minute and then shut it off and removed the float bowl. It was FULL! 

I re-installed the air filter and side cover and went for a short ride just to test the performance. It was greatly improved and only hinted at a big of richness just off-idle. I removed the mismatched aftermarket needles… yes they were not a match on the same set of carbs, too! I compared all needles from both carbs and discovered that the D3 needle was match for the other brass needle and the two silver needles were also about the same. I dropped the needles down to the #2 groove and reinstalled them again. Suddenly, the bike felt and sounded like a almost normal CL175 Honda twin again. I brought my fuse tester with me, just in case, but made the full downhill test run back to the place where the fuse had blown before and then turned back around for the return leg. It was running well; as well as it could on aftermarket carbs and a mix of non-OEM carb bits.

Bill M. was on his way down to pick up the CL175 and leave me an XR75, plus the chassis for the SL100 engine that I had finished rebuilding. Obviously, I was very pleased to have finally conquered the worst of the bike’s problems and felt it was safe to drive regularly. I would feel even better once the OEM carb parts arrived from Holland. At some point the original carbs can be returned to the engine, for which they were intended.


I lost track of the actual hours of work devoted to analyzing and developing some strategies for a successful outcome. In the end there is a sense satisfaction that perhaps I learned something new, when facing similar challenges in the future.


Well, it certainly had me going round and round, unfortunately overlooking what was obvious in hindsight. It’s difficult enough to repair these old bikes given the lack of original parts, here in the 21st Century. While the aftermarket vendors try to supply the needs of owners, unfortunately, the lack of quality control and design detail can cause a world of frustration, in cases such as this.


In situations, such as this, when nothing makes sense, even though you think that everything has been done correctly, you have to backtrack and dig deep into the minutiae of the smallest details. A small discrepancy can derail your best efforts to troubleshoot and diagnose the problem. In the end, you will find success.


Bill Silver

aka MrHonda

www.vintagehonda.com

08/2024



Wednesday, August 28, 2024

CL175K3 Blue tape special

A few months ago, my friend Bill M. contacted me about “rebuilding” a CL175K3 engine for a project that he was doing for one of his friends. The plan was for him to bring me the engine to rebuild and he would be restoring the chasssis then bringing that down here for the engine installation and then put all the bits and pieces back together again. The bike was purchased as a partially started project from a previous owner and the whole bike was disassembled.



The engine arrived with the lower end in a screwed-together wooden box, while the top end and carburetors were in separate bins. After about 15 minutes of undoing all of the wood screws, the bottom was revealed to have a damaged kickstarter shaft. A new one was provided, so this was obviously going to be a full teardown and repair. The engine was otherwise in decent condition internally, but required cylinder honing, valve seat repairs, vapor blasting and installation of the fresh parts. It was still on STD bore and the pistons were reused along with new rings.


Whoever started the project, was apparently new to the hobby, so virtually each and every single part was labeled with blue masking tape, including all of the wire connectors. So, part of the process was to peel off all of the blue tape from the components and clean the parts of  the remaining adhesive.


The engine rebuild was mostly uneventful, apart from having to run around town, hauling the parts back and forth to my friend with the vapor blasting machine. A set of aftermarket carbs were brought along with the engine parts, but the originals seemed to be worthy of a good cleaning and kit installation.


Once the engine was completed, it sat for a couple of months while I was doing several other projects and waiting for Bill M. to finish the chassis and find time to marry the two project halves together. Finally, in Aug, fully four months later, the the chassis was delivered on an early morning trip from OC and work began. The engine was shoehorned into the frame and all of the engine bolts fed into their respective places. Bill had brought down a copy of the parts manual, so we could refresh ourselves about what went where and what might be missing. Slowly, on a very hot day, the bike began to take shape, rising like a Phoenix from the pile of parts emerging from their blue-taped packages.


The CL175K3 model is the only one that had a high-mounted front fender, which was composed of several various adapters to fit the bottom of the fork stem. According to some parts lists, the K3 was sold in 1969-70. The wiring harness was fed back into the frame recesses at the back of the chassis and the ignition switch mounted up on the forward bracket, beneath the gas tank on the left side. A charged lead-acid battery was pulled from its box and dropped into the battery box. These batteries have a vent tube that needs to be routed carefully, to prevent acid damage to the chassis during operation. I situated the battery so the vent was towards the rear of the battery box.


At first only the neutral light came on when the ignition switch was switched to the ON position. The bike had been supplied with a little aftermarket cube bridge rectifier in place of the OEM selenium unit which mounts on the inside of the frame behind the carburetors. When I touched the battery ground lead to the battery there was a strong arc, indicating some kind of short circuit. The only thing that is active when the key is OFF is the rectifier, so I assumed that it had a defect and we ordered a $100 OEM unit from an eBay seller.


In the meantime I was puzzling over the other electrical system issues, starting with the tail light function. Whenever a bike chassis is powdercoated or even painted, all of the ground paths need to be established again, as the powdercoat becomes an insulator to electrical circuit pathways. I had cleaned off the usual places for proper grounding but when I checked the power to the tail light, it showed power to and through the bulb, but my test light lit up only when it was grounded back to the battery. Studying a copy of the online wiring diagram didn’t show any separate ground path to the harness wires, except though the various components, but they were still mostly isolated from a good ground path. I finally eyed a single green female ground connector by the battery with no place to go. I made up a jumper wire and connected it to the female connector and grounded the other end where the turnsignal flasher mount bolts to the frame. Success! All the lights came on and power seemed to be restored to all of the lighting and other functions.


A few days later, the spendy orange rectifier arrived and was installed after removing the left side carburetor again. The mounting stud was well grounded and I was looking forward to completing the electrical system. But, as soon as I touched the two harness connectors together, there was a big flash and wires started getting melted! I quickly pulled the two connectors apart and reviewed the wire colors for each side. The harness side connector had the red hot wire across from the green ground wire, but these colors were swapped on the rectifier side. Obviously this was a dead short to ground for the battery feed line. I pushed the wire connectors out of the harness side to match the rectifier colors and plugged them back together again, gently. There was still some arcing going on, but less than before.


Finally, I thought to check the battery connections and finally noticed that the battery was installed BACKWARDS! This was the cause of all of the electrical arcing from the rectifiers, both the aftermarket one and the OEM version. MrHonda had a senior moment and hadn’t paid attention to the battery polarity. The battery was installed with the markings turned away from me and I was using the position of the battery vent tube as the indicator of the orientation of the battery when mounted in the frame. It all became clear in an instant and now the damaged rectifier needed to be removed and replaced again. In looking at the rectifier, only the green ground wire that comes from the connector to the side of the rectifier mount was fried, so the rectifier through bolt was carefully removed, and a new wire with a ring terminal was installed. With everything re-attached, there was no arcing when the battery was re-connected and all of the rest of the electrical functions were operating normally.


In order for the Scrambler exhaust system to be installed, the left side air filter must be attached to the carb and then the left side cover snapped into place. Then, the wiggly Scrambler exhaust pipes can be hooked back into the exhaust ports and attached at the rear mount. That done, the bike was rolled off the work table and down to the driveway where the fuel tank was waiting to be installed.


The petcock appeared to be an aftermarket piece, already connected to fresh hoses and inline filters. The petcock mounting bolt was missing the sealing washer, so I had to dig up one from my pile of leftover carburetor parts. Then the screw wouldn’t go into the tank without chasing the threads with a 6mmtap. Once everything was put together, some fuel was poured into the tank and the moment of excitement arrives. The original kickstarter which had flattened out splines was replaced with an aftermarket piece which was an inch shorter than the OEM unit. This made kickstarting a bit of a chore as it was near the rear footpeg. I had already checked the ignition timing, so it should have fired up quickly. After a dozen kicks it coughed to life reluctantly, then stalled out. I looked down to see gasoline dripping down from the left side of the engine and oil dripping down on the right side of the engine. Now what!!!!!?!?!??!


The left side carburetor was dripping from the overflow tube and even with the petcock turned to the OFF position, there was still a persistent leak. The right side leak was from the oil filter cover, which had been sealed up with new o-rings, but continued to leak after several inspections and measuring the o-rings for the proper sizes. I happened to have a spare outer o-ring so stacked two on that side and the oil leak ceased. I tried to access the left side carburetor float bowl to see if something was obviously evident, perhaps with a failing float from a pinhole. It always seems that if you are working on a Scrambler of any size the left side carburetor is the one that will have an issue.


The exhaust port gaskets were supplied from an ancient gasket kit and consisted of some asbestos wrapped with copper wire. These compress down to nothing when installed, and the result was exhaust leaks at the flanges. The pipe packing that seals the two exhaust pipes together at the rear junction was mostly gone, so there as a leak back there, as well. So, the tank came back off so the petcock could be rechecked for the dripping issue and the exhaust removed again for new seals. With the exhaust removed the carburetors could be reinspected again. The left side drips had stopped, but when the engine was running briefly, it sounded like it was running rich on the right side, which was confirmed by a black plug when removed for a compression check,


New parts were ordered and the bike’s carburetors removed and checked again. There were aftermarket kit parts installed and they are often not to OEM specifications.

In the meantime, more electrical work was required to reconnect all of the wires inside the headlight shell. The rubberized instrument lights that pushed up inside holes in the back of the speedometer and tachometer were mostly all toast. A previous person had wrapped a lot of black electrical tape around the bulb sockets in an attempt to keep them situated in the lighting holes, but obviously, this was a failed attempt. I happened to have a string of instrument light wiring from a different model, but all of the socket rubbers were in great shape. I snipped here and there, finally getting them all spliced in for functioning instrument lighting. I had to special order the 12v 3w light bulbs to fill all the empty holes.

When I went to fit the headlight assembly back on, the left-right adjustment screw and bracket were broken away from the back of the reflector. When the rim was test-fitted to the headlight shell, it became obvious that the shell, which is metal, was out of round and painted that way along with the other metal parts (plastic side covers) on the bike.


I had some various woodworking clamps hanging in the shop and one was big enough to reach around the perimeter of the shell and with some strong twists of the clamp, brought the shell back to a circle once again, without damaging the painted surface. The left side headlight bracket had a bend in it, which needed straightening. The bike had surely been crashed at some point and the damage was left unattended by the painter and previous owner. Finally, all the lights started to function, but the headlight assembly isn’t centered with the midline of the front wheel, so more work needs to be done there.


The bike was run on and off my work table, to the driveway near the garage door opening for follow-up work on the fuel system. Repeated removal, inspection, cleaning, adjusting and re-installing of the carburetors failed to remedy the fuel fouling of the spark plugs. A more detailed examination of the associated components in the ignition and fuel systems didn’t give a solid clue as to the cause of the carburetor problem. It was finally resolved when a comparison of the needles, slides and idle jets revealed that the aftermarket parts were not a perfect match to the OEM parts.


See the next story on CL175 troubleshooting for how the process was performed and how it was finally resolved after hours of trial and error, including the replacement of the stock carbs with some Chinese copies. 2024 has brought in very difficult project bikes to sort out and rebuild to specs. It ain’t easy being MrHonda sometimes.


Bill Silver

www.vintagehonda.com

8/2024