Tuesday, August 1, 2023

Double or nothing… CB77 and CB550 Part 1

My friend, Dave, who lives 165 miles away in Santa Clarita, CA sold a rough, but mostly complete CB77 a couple of years ago. The engine was severely seized and it took drastic measures to get it apart and rebuilt. Eventually, it did run again and was sold during the pandemic.

Fast forward 2 years: Dave calls to say that he found a “red” CB77 that had belonged to a Honda service manager that had been sitting on a patio for 7 years. Dave bought it and brought it home for some cosmetic cleaning and sent photos. The bike was a 1965 series chassis/engine, but had a pre-64 front brake panel and a NOS early style speedo-tach installed. The whole front fork assembly had been chrome-plated at some point in time, giving the bike a unique almost chopper-style look, but the forks were not extended. The tank and fenders were painted red, but the chassis was black.

Dave’s other “project,” that he was anxious to get running was a 1974 CB550K model, which he bought cheap due to a seized engine. The speedometer showed about 15k miles and so he had a local mechanic disassemble the top end to gauge the damage. The mechanic covered the pistons with a cloth rag, covered it all with clear shipping tape to keep out the dust/bugs and Dave put it in his shed.. for about 3 years.

Dave proposed one of two scenarios… Fix the CB550 to get it running and he would give me the CB77 OR…. Fix the CB550 and the CB77 and he would pay me for both repairs.

At the time, a motorcycle wrangler, who is located in Ventura, CA (200 miles from me) had offered 3 Honda 305 bottom-end engines, plus a stack of heads and cylinders for $305. Ventura is 45 minutes away from Santa Clarita, so I reluctantly decided to make the journey in my 2015 Tacoma and fetch as much as possible.

The trip to Ventura took 4 hours on a somewhat light traffic Tuesday morning, starting from San Diego. I met Tim, the owner at a dusty, warehouse in Ventura, next to a couple of Harley repair shops. He opened the sliding door on the alley and we went inside to survey his pile of misc bikes and parts. When he posted the photos of the engines, one caught my eye, as it appeared to have a crankshaft-mounted magneto ignition system in place of the stator/rotor. That motor was a CL72 and he had the matching frame in a pile of other CL frames. At first, he was going to keep the CL72 package and replace it with one other CL77 bottom end, but then relented and threw in the CL72 engine and frame, as we were not able to extract the magneto with hand tools that I brought.

This load pretty much filled the space behind my seat on the X-tra Cab Tacoma, plus half of the bed. I called Dave and told him that I would have to drop off the engines when I picked up his bikes, then he could bring all of that down when he came for one or both of the bikes. At Dave’s, we loaded the two bikes and associated parts, which filled up the bed, so Dave stashed the 305 parts in his shed where the bikes had been sleeping. Off I went on the return trip to San Diego, leaving at 4pm, heading into afternoon rush hour LA traffic. My WAZE GPS app on the phone took me on and off the freeway, down side streets, back on different freeways, and eventually on the rest of the I-5 southbound traffic. Another 4.5 hours later and 459 miles, the Tacoma came to rest back home again. I just left everything in the truck, backed into the driveway, and called it a day.

On Wednesday morning, I unloaded the truck and sorted through boxes of parts that were removed from the CB550. The cylinder head and cylinder block still had remnants of the factory head gasket material which was fused to the mating surfaces. When the rags were removed from the pistons on the crankcase, all four were seized to the rods and wouldn’t even rock back and forth on the wrist pins. Ugh! Flooding the pistons and pins with PB Blaster, I used giant Channel-Lock pliers to rotate the pistons on the pins, slowly loosening them up. Sitting in the shed for 3 years in a location that had temperatures ranging from freezing to 115 degrees, the air inside the engine cases, condensed moisture inside the pistons and it ran into the small oiling holes in the top of the rods, causing rust to form between the pin and rod end. BTW the last license tags on the plate were 1982!

                                              Four pistons, frozen in time. Wrist pins rusted to the rods.

Just digging out the wrist pin clips was a chore as the moisture had caused corrosion between the steel clip and the alloy piston. Eventually, I was able to extract a clip from the #1 piston. I have a heavy-duty piston pin pusher tool that I bought from a man who was selling Benelli parts at a time when I had bought a Benelli Sei, 6-cylinder 750 bike. The tool had a shoulder for a 15mm pin but the end was tapered down so that it fit into a 14mm pin on the CB550 rod. Using the tool, with the help of a CB77 fork tube on the handle, I was able to force out one pin at a time, until all four pistons were removed. This was a one-hour process of very physical work, but at least they were free from the engine, to be replaced by some inexpensive piston kits from David Silver Spares. The cylinders had some staining on the walls, but were not heavily corroded, so a hone job and fresh STD pistons should remedy the top-end issues.

Cleaning off the base gasket material and then the head gasket leftovers from the head and cylinder took 3 hours of concentrated scraping, one little piece at a time, until it was gone. The original gaskets were probably asbestos and Honda added some kind of adhesive to the head gasket to prevent the persistent oil leaks that plagued Honda fours for many years. Once the engine was heated up and running, the gaskets were fused to the cylinder head and cylinders, making removal very difficult.

The head was disassembled and all the valves cleaned, seats lapped, and stem seals replaced. Top-end gasket sets are available from the aftermarket but I have had several poorly made gasket sets that didn’t even line up the bolt holes, so I searched for an OEM gasket set. These are in short supply as well, plus Honda did offer some non-asbestos kits with an -S01 suffix, but the only one I could find was in Germany on eBay. It took about 10 days to get to me.

More bits came from 4into1.com to complete the engine work, but the last task will be the carburetors, which are not easily disassembled and cleaned, plus the OEM gasket kits are about $40 each. Most of the aftermarket carb kits are from Keyster and they don’t have a good reputation for accuracy in the calibration of jets and slide needles. Whenever possible, reusing the original OEM carb hard parts is best, with the use of the a/m kits for the soft parts and float valves.

I tackled the carbs while waiting for pistons and gaskets from the UK and Germany, respectively. The #4 carburetor had water damage and the emulsion tube was heavily corroded and plugged up. The carbs had to come apart to change the fuel feed T-fitting o-rings, so you have to play watchmaker to tease everything apart, not lose all the little spring-loaded components and eventually, reassemble it all again. I spent over 3 hours in the disassembly, treating the single carb body to a little phosphoric acid bath and then replacing the o-rings. The carbs just fit into the Harbor Freight home-sized ultrasonic cleaner and the combination of Pine-Sol and water did a decent job of cleaning surfaces and passages. All of the steel parts of the linkages had some rust and corrosion, so you just have to take your time in the reassembly process.

There will be at least ten hours of labor involved, just with the CB550 engine repairs. The CB77 engine is frozen, of course, so the fate of that bike is yet to be determined.  

End of Part 1.       

Bill Silver aka MrHonda


  1. Bill.............thanks for the story so far! Several of us have been down the same road! I just completed rebuilding my CB750 SOHC motor that I race for landspeed records at Bonneville. One of these days I will get back to my CL72 projects..........I need to rebuild 2 motors.

    We have talked and exchanged a few parts over the years and I have your BOOK for the 72-77 models. I was in Wisconsin for many years but now spend time in Az and ID while traveling with an RV.

  2. I'm pretty sure the parts stash you bought was one I'd seen on Craigslist! By the time I reached out to buy it, I got a response that it was sold. The guy was offering me CL77 frame parts but I was only interested in the engine parts. I recall seeing heads with broken fins but nonetheless plenty of parts for the money. It's a small community of enthusiasts so I should have known you were the buyer!