The next day…the next bike.
So, while I was waiting for parts from Germany and the UK, I removed the carburetors from the CB77. The left side looked normal with old fuel solids and a clean intake port. The right side carb was full of water corrosion and scale, as was the whole intake port. This was certainly a good reason for a seized engine condition.
I slid a little jack under the oil pump drain bolt and removed the engine mount bolts and disconnected the electrical connections. I use the little wooden Harbor Freight dollies to move the engines around the shop and to work on the engines for disassembly. The cylinder head came off easily as the master link for the cam chain was just below the top cover surface.
Sliding the head off of the studs allowed a big splash of penetrating oil that had been used in an effort to soften up the offending water and rust build-up inside the cylinder. The pistons were nearly even in the bores, about half-way down the cylinders. This allowed the cylinders and pistons to be raised up in order to allow use of an air hammer to try to drive down the affected piston.
I’m sure my neighbors didn’t appreciate 20 minutes of nearly continuous air-hammer operation as the piston very slowly moved downwards in the affected cylinder. By the time it got to the bottom, the liner had cracked, but at least the piston was free of the cylinders and the rest of the disassembly could continue.
Based upon the worn counter-shaft sprocket teeth, the engine and bike probably have 20k miles, but with the replacement NOS speedometer, there is no verification of what actual miles are on the whole bike. The clutch side components were disassembled, in surprisingly good condition apart from a very stretched-out primary chain. The little thrust washer for the oil filter had been installed on the inside of the filter body, incorrectly.
Splitting the cases revealed some interesting features. The gear dog engagement was well within specs and most surprisingly the low gear bushing had a nice sharp edges ridge in the center and was still a good fit into the low gear opening. Even the kickstarter pawl was not deeply worn down. But in cleaning off the top gear/output shaft, the whole internal bushing just slid out. That was a first-time discovery for me. I had a spare gear with the correct back-cut gear dogs, so it was put into service after cleaning up. The shift drum and forks showed minimal wear, so the cases were reassembled.
The cylinder head was the next job. I tried using some oven cleaner to strip off 50 years of grease and corrosion, which did a pretty good job but left some traces of a chemical reaction in the metal surfaces. The head was disassembled and the packed-on goo from the penetrating oil and old rust was removed. The valves didn’t appear to have a lot of carbon buildup, so someone had probably been into the engine once before, at least the top end. All of the lower-end fasteners were obviously not disturbed in the past, so it was still a puzzle how the transmission parts were still in such good shape. Apart from the usual layer of grit and oil solids in the bottom case, the transmission gears all looked pretty clean, so it must have gotten regular oil changes in the past.
Looking through the stack of heads and cylinders that I had purchased from Tim in Ventura, I found a die-cast, late-model set of cylinders with a nice camchain tensioner. The cylinder bores looked like they had been machined and not reused. It turned out that they were on. .25 oversize and cleaned up fine with my large hone. The next trick was to find .25 pistons and rings at a reasonable price. Fortunately, I called my friend Ed Moore, who has been rebuilding these engines for many years, and he came up with some .25 pistons, but no rings. We made a deal on the piston set and I found an almost reasonable set of new OEM rings for $75.
I removed the valves from the cylinder head and cleaned them on a bench grinder wire wheel. They had somewhat wide seats, but for this engine, they would be fully serviceable. Lapping in the valves to the seats yielded good results, so the rest of the head was assembled with just some concerns about the cam sprocket return springs. I purchased new springs from Tim McDowell, but they still didn’t quite take up all the slack in the advancer return weights. With this little amount of free-play, the spark timing will advance slightly when the engine is idling, which isn’t necessarily a bad thing. Stock ignition timing is 5 degrees before TDC and these engines prefer to idle more like 10 degrees before TDC. On a somewhat budget-restricted engine build like this, some compromises are going to be made.
The aftermarket pistons from SK consistently come with piston pin bores that are slightly too tight, so pins cannot be easily pressed into the pistons. I have a 15mm ball hone that will take out just a bit of material enough to make the pin fit normally. These pistons have a Dream-style piston crown. The machining appears to create a lower piston profile than that of regular CB pistons, but in practice, they tend to increase the compression readings when installed.
The oil filter was in need of cleaning, of course, and the oil pump screen was still usable after the gaskets were pared away from the screen flange. New gaskets and seals, plus a screw kit and the return springs all came from Tim McDowell’s site: www.classichondarestoration.com, and arrived in just a couple of days.
To remedy the water-damaged carburetor, I was able to pull out a good spare carb body from the extras that came down with the bike, so that issue was remedied without extra expense.
The replacement cylinder block for the engine was a die-cast unit that uses the narrow tensioner. I was happy to have a ready-to-go cylinder except for the broken fins on the top and in the middle of the cylinder block. Rob North managed to squeeze me into his work schedule and fix the fins so I could wrap up the engine work.
Dave had asked me if there was a problem with the starter motor. I seldom see problems with them, so I cleaned it up and added a little silver paint to freshen it up. Once the engine was finalized and re-installed, the starter button only brought forth a “click” and then nothing more. The tags on the bike were from 1977, so I thought that the solenoid might have had corrosion buildup on the internal contacts. Removed and disassembled, the solenoid really wasn’t having issues, it appeared. So, once I knew that the battery power was getting to the starter motor, I knew that the starter had to come back out for inspection.
Taking the wrap-around cover off the brush end of the starter revealed a stuck contact brush in the holder, but no signs of corrosion that would cause such a problem. I cleaned the brush holder carefully, but every time the brush was inserted, it would jam up again. Finally, I carefully filed a little material off of the sides of the brush until it slid easily through the holder.
I had already replaced the starter clutch rollers, springs, and caps, so that wouldn’t be an issue, but once the starter was replaced, the motor would try to pull the engine over with the starter chain, but it would stall out and make a loud screeching sound. The last place to visit was the starter drive end, so the motor was removed yet again and the drive removed. The three screws that held the drive unit were not factory tight, so someone must have been wrestling with this problem previously. There wasn’t a lot of grease inside the planetary gears and sun gear, and most of it was dried out. Cleaning the sun gear, I discovered a groove in the outside of the piece that clicked in an old memory of having these starters apart before and that there was supposed to be a steel pin that anchored the sun gear to the housing. All I was able to find was some tiny pieces of pin, buried in the old grease.
I searched through my bits and pieces of Honda parts and didn’t find anything that was that small. Finally, I discovered a 1/16” drill bit that fits the housing hole just about right. I shortened up the bit so that just the smooth shank was a nice fit and reassembled the drive unit with fresh grease. Finally, the starter motor kicked the engine over with vigor and it started up quickly. I was feeding the carbs off of a remote fuel bottle and let it idle for a few minutes while I checked for oil leaks or other issues. There was no smoke out of the header pipes and no leaks so it was good to go, as far as I could see.
As always, there were side issues that took more time and running around to solve. The ignition switch which had a common T series key started to seize up during the first few minutes of getting powered up after 45 years. I took it out, noticing that a few wires were not installed correctly on the back. On top of that, the whole wiring harness was installed over the frame tube instead of beneath it back by the battery box. So, more time was taken to cut through all of the tie-wraps and reposition everything. Inside the headlight shell, the speedometer bulb covers had melted in place, so the whole speedo was removed and the rubber chipped off of the bulb sockets, which were empty when removed. New bulbs were installed and a newer light bulb harness was installed. The neutral light lead was missing as well, plus there was no headlight rim. There was a new bulb in the box of spares, so I offered up my last NOS headlight rim and clips to put the headlight back to normal again. The bike had huge 6-bend handlebars, so the starter wire had been extended to connect to the harness leads. The dimmer switch was found in the box of spares, with a partially set of extended wires that were never completed. Bikes like this will drive you crazy with all the little detail issues that need five or ten or fifteen minutes or more to resolve, not including finding the necessary parts to put it all together again.
Dave came down a few days later, on a Saturday morning, leaving his house at 4am. He arrived in Spring Valley at 7:30 and after some test running of both bikes, they were eventually loaded up on his 3-rail trailer, and off he went back to Santa Clarita. He was pleased that I was able to revive these two neglected bikes and has plans to get them fully cleaned up and licensed for the street.
It was a huge undertaking for me, especially having stuck piston pins and pistons in the two bikes. I was happy to get a final check for the work and parts, then send both bikes off to new lives in Santa Clarita (actually Canyon Country, according to the ZIP code).
Bill Silver aka MrHonda
08.01.23
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