When I purchased a lot of Honda 250-305 parts from LA, the purchase included three bikes; two CL72 Scramblers and one CB77 Super Hawk. The CB77s are my favorite and the speedometer only showed 8k miles and the original front tire confirmed the originality of the chassis, it would appear.
However, like so many of these old bikes, the motor was “stuck,” which usually happens when people leave the spark plugs out, the air filters off while the bikes are parked outside and moisture builds up inside the cylinder and rusts the piston rings to the cylinder walls. Seldom an easy fix because when/if you get the piston to break loose the rings are all corroded into the piston’s ring lands and you won’t have much compression anyway.
I brought the bike up to the house, from the storage space I am renting, to see if it could be salvaged or not. The tool box was all rotted with the solenoid hanging off the bottom and someone had put some kind of narrow, goofy rear fender on it, which was 2” too narrow and not mounted well anyway. The frame and headlight shell were black, but as I began to strip stuff off the chassis, I could see BLUE paint underneath, just like my rejuvenated 1961 CB77!
Draining the oil, I noticed that the oil pump was from a Scrambler, not the original smooth bottom CB/CA pump. Then, I could see that motor mount bolts were substituted and some installed backwards, so I knew that it had been apart before for unknown reasons. Once it was dropped onto the bike lift cradle that I use to load/unload the 115lb motors, I transported it to the work bench to see what surprises were in store for me this time.
Loosening the top eight cylinder head nuts, allowed the top cylinder head cover to be removed, revealing a lot of worn/torn metal parts. The end of the points cam, which runs through the right side camshaft was blued from excessive heat and the cam seal was melted from the overheated parts it was contacting. The camshafts were all scored deeply and the cam followers were going to be a reflection of the same lack of lubricant to the top end. Lots of scrap metal parts to toss, just from there, but WHY?
With the top cylinder head cover removed, I noticed that the camchain master link was near the top, so I proceeded to reach down with a magnet and small tools to disassemble the master link and drop the camchain down, allowing easy removal of the cylinder head. Once the head was off, I was faced with the usual layer of rusted corrosion build-up on the right side piston, while the left piston/cylinder were pretty much clean and looked like they would move without force. I had been spraying some “Prolong” penetrating oil into the cylinders which was given to me by a customer who swore that it was the best product he had ever used to loosen stuck/rusted parts. I made sure that there was plenty of the lubricant surrounding the piston, while I applied my “steering wheel puller” tool to the top of the piston crown. With the tool secured, I used a long 3/8” drive ratchet and began to twist the central bolt downwards against the piston crown. It appeared to be pretty resistant to any movement using moderate force, so I bore down on it with a little extra muscle and suddenly there was a “cracking” sound and then the tool relaxed momentarily. I turned the screw down further and the piston just went down under the pressure with surprisingly little force. It took a little bit of jacking back and forth to keep the cylinders level as the pistons exited the bottoms of the bores, but the whole process probably took about ten minutes from start to finish.
With the pistons removed, I checked the rods, which felt somewhat excessively worn side-to-side, but not necessarily up and down. The next step was to remove the oil filter and clutch cover, to see what else was damaged.
As I remove the outer oil filter cover plate, the shaft came along with the plate, as usual, but I was astonished to see the oil filter parts lying inside, all disassembled to a certain degree. The snap ring and the outer filter cover cap were loose and showed deep grooving from spinning inside the inner filter housing. Even the thin o-ring was loose and twisted around inside the filter housing case. I saw no signs of the thrust washer and the little locating pin that keeps everything in place. Apparently, these parts were misplaced or forgotten and the engine assembled without them. It was clear that the cover had come loose and then dumped out any and all oil that was being pumped through the clutch cover into the filter plate channels. This short-circuiting of the oil flow, lead to a complete starvation of the critical top end components and their subsequent destruction. But that wasn’t the only problem causing oil flow issues.
The starter clutch had been removed from the rotor and a CL72 oil seal installed in the cases, when the engine was reassembled. The difference between the CB and CL crankshafts is the tiny oil feed hole, which is needed to lubricate the starter clutch hub. The CL cranks don’t need the oil hole, because they don’t have electric starters. So, in that case, the hole is not drilled into the base of the crankshaft snout. On the CB crankshafts, the oil hole is drilled outside of the CL seal lip, so oil is flung out of the feed oil as soon as the engine cranks up, when that seal/crankshaft combo is attempted. MUST HAVE MADE A MESS, don’t you think?
It is hard to say how long the bike was run in this condition, but there was a lot of mud packed up underneath the crankcase, so it must have been running for a good half hour or so, I would guess. Generally the pistons will seize first, when oil is lost in the crankcases. The left side piston did show some signs of seizing, but the right side is too corroded to really see what happened there, prior to the introduction of water/moisture that eventually caused that side to seize solid.
As the disassembly continued, I discovered that the transmission was barely catching 3rd gear, when shifted by hand and the gear was quite loose on the transmission shaft. This gear is attached to the shaft by a set of gear cotters, held in place with a snap ring. When the ring was removed, the gear cotters came out in shattered pieces. I have seen them broken in half, but not in multiple tiny parts before.
The usual set of kickstarter pawl, spring/plunger, a new low gear bushing and sets of gear cotters will bring most of the function to normal, once again. I have to check the shift drum for wear on the track apex, as the shift fork seemed to be looser at that spot than other portions of the track grooves.
Next up, all parts get cleaned, re-inspected, replaced as necessary and eventually reinstalled as a running, correctly assembled CB77 engine, once again. Time to go dig through those parts now…