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A 1962 CB77 arrives with “leaky gut syndrome”… and we find a cure!

Repair steps for persistent clutch pushrod seal leaks. Post repairs with no oil leaks beneath the motor!
Repair steps for persistent clutch pushrod seal leaks. Post repairs with no oil leaks beneath the motor!
Bill Silver

Just last week, I had a puzzled questioner about a bike which had a persistent oil leak problem at the pushrod shaft seal. He was beyond frustrated and wanted to know what could be done to fix it. I asked him about using a new seal and pushrod, which he had already done, so at that moment MrHonda was somewhat stumped for a viable solution. Sure enough, just days later, here comes an opportunity to see the same issue and create a solution.

At a recent “Mods and Rockers” bike run and show, here in San Diego, I spied a 1962 CB77 Honda Super Hawk across the parking lot. When I met up with the owner, he reminded me that this was the bike he had asked questions about within the past month. It was one of those eBay purchases and some issues were not fully revealed at the time of sale, apparently. The owner asked if I could go over the bike for him, as he was having slipping clutch problems, poor performance from the engine and other minor concerns. I agreed to have a look and on the following Saturday, the CB77 came in for an inspection and estimate of repairs. While sitting on its centerstand, it “marked its territory” with a few drops of oil.

Although registered as a 1963 model, the serial numbers were clearly from the 1962 production. On close inspection, it was kind of a “Bitsa” bike, having the correct frame/engine, tank and wheels, tail light with the “short lens” out back, but late- model carbs (with a throttle cable about a foot too long), speedo-tach, 1-piece exhaust systems and an aftermarket copy seat. The wrong battery was installed, the wiring a bit of a mess and there were oil leaks here and there.

I replaced seals as needed. Once I replaced the k/s, starter clutch hub and pushrod seals, I buttoned it up to check the ignition timing and carburetion. While the bike was sitting there idling, oil started dripping out of the bottom of the k/s cover. Pulled it a back apart and sure enough the seal was leaking oil past the pushrod, even at idle. I happened to have a NOS OEM seal and installed it... same result.

Finally, I checked the pushrod for sideplay and found probably .006"-.008" I put the pushrod in some spare output shafts and discovered that they had next to no sideplay even without the seal in place. I tried putting an o-ring on the pushrod, behind the seal, but it kept the seal from installing all the way inside the shaft recess. The only way I could see to fix the problem was to countersink the end of the bushing so the o-ring would seat back inside the recessed hole. I found a 27/64 drill bit that was the same OD as the “Harbor Freight” metric o-ring that I had on hand and drilled a hole just back into the bushing far enough to allow the o-ring to seat. This allowed the seal to go back all the way deep into the end of the outputs shaft. The o-ring helps to steady the pushrod in the hole and so far, NO LEAKS!

Obviously, the real fix is to replace the transmission output shaft, but I think this should work for short-term riding. I haven't had to address this problem before, but once the question was asked, the universe supplied the opportunity for me to experience the problem and create a solution.

Once the clutch was repaired, a test ride proved out that all repairs so far were correct and no oil was spotting the ground after the run down the road to the Post Office. The bike was low on power, but a plug read looked like they were not too lean. I assumed that the carbs had #135 main jets, which is standard for stock CB77s. This bike had one piece muffler systems installed, but no baffles were present at the back. I was shocked to find #125 ISO threaded jets in the main jet holders and wondered how it could have been ridden in on the freeway without seizing. That answer to that question was that the ignition timing was so far retarded that the engine couldn’t make enough power/heat to cause piston seizures. If the ignition timing had been correct, I would have expected seized pistons, oil smoke and breather residues. I have to say that the engine is a bit “clattery” but most of the noise is from the wrist pin holes in the rods being oval-shaped due to wear.

I plugged in some #140 mains, which were made for me last year, specifically for the CB77 applications. All the early bikes have JIS thread pitches on the jets, so new ones had to be special ordered. The bike felt a bit flat in the mid-range, so I suspect that some Keyster needles may have been installed during a carb rebuild. Keyster parts have had a reputation for rich metering in the past, so pulling them out for inspection is on the “to do” list next.

Whoever built the bike had placed a weak spring on the centerstand, which allowed the stand to bounce up and down as you drove down the road. The normal centerstand return spring is quite a chore to install, especially on the bike, but looking closer to the spring and hardware in that location, it was apparent that someone had replaced the two short footpeg anchor bolts with one LONG through bolt, which anchored the footplates well, but fouled the centerstand return spring path.

More problems arose when the seat was to be installed. The wide, thin metal forward mounts were hitting the battery’s positive post during seat installation process. The mount was narrowed slightly and some rigid foam placed over the terminal, however installing the seat on the two forward frame mounts drove the seat mount and pan into the thinly protected battery terminal, causing some smoke and burning aromas. The only way around it is to replace the battery with the correct one, but in the meantime the seat had to be cocked up on the left side with the seat mount tabs sitting on top of the frame mount lugs, instead of hooking underneath. At some point the ground wire for the solid-state regulator/rectifier had gotten trapped between the seat mount and the frame, pinching it nearly into two pieces. If the wire breaks, the charging system quits because the module wasn’t hard bolted to the chassis mounts.

These are typical issues found on many of today’s used and/or refurbished vintage Hondas. A decent Honda CL90 Scrambler followed me home on Sunday, so it is next to undergo scrutiny and repairs in the weeks to come. Stay tuned….

Bill “MrHonda” Silver

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