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