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