Well, they just won’t stop coming. Latest bike is an early 1964 CL72, painted orange, supposedly from the selling dealer with some 1963 features, like a sand-cast front hub and even the oil pump. It was in overall nice condition, but the owner complained about the transmission shifting erratically and the engine had been freed up after weeks of soaking and heat until it finally freed up. He was able to get it started and running, but the engine rpms were uneven and the head gasket was leaking. He had also swapped out the clutch fiber plates with Barnett performance parts, but kept the original springs.
After drop-off and initial evaluation, I dove into removing the 100lb lump and began tearing it down for inspection and a full overhaul. I had to drill the heads off of three of four cylinder head side cover screws to start with. Once the top cylinder head cover was removed, the camshaft lobes looked a bit rusty around the edges. Apparently, the bike was either mostly original or rebuilt and then left sitting for something like 20 years. The camchain tensioner was removed at the back and the roller was seized up solid. Somehow the long-term storage had created some moisture inside the tensioner roller pin and bearing, locking it up.
Pulling the cylinder head off, yielded some surprises. Usually, when “stuck” engines are freed up, the result is the rings have been stuck in the piston ring lands, causing a loss of compression. The owner initially tried to do a compression check with a push-in gauge and found 90 on the left and 140 on the right side. Before he left, we used my screw-in compression gauge and got 175-180 readings on both sides! The tops of the pistons had a little layer of black carbon from oil burning and perhaps carb metering problems. When the cylinders were raised, the rings were all free in the pistons and the pistons were all STD size. The edges of the rings were really sharp, having scrubbed all the corrosion off the cylinder walls that had kept the pistons stuck in the bores. Removing the top compression ring and putting it in the bottom of the cylinder bore gave me a .032” gap, which should have been about .006-008” normally.
I used a ball-hone to scrub the cylinder walls, to determine how much corrosion damage had occurred but the bores looked surprisingly clean. There was a bit of a corrosion ridge/ring just where the top ring lands, but I was seriously considering just buying new rings and re-using the pistons again with the cleaned up bores. Finding machine shops here in San Diego, has become increasingly difficult as the guys who have been in the business for many years are aging out and suffering from various ailments.
Calling my friend Tim McDowell in MD, to order some gaskets, seals and a screw kit, lead the conversation to mention that he had a whole set of cylinders, bored to. .50 oversize with pistons, rings, clips all ready to go! We made a deal on the whole package and it was shipped out quickly.
In the meantime, the bottom end was dismantled including the revised clutch parts. Nothing much was amiss but the oil filter was somewhat tight on the shaft. Once the cases were cleaned off of all the clutch and shifter hardware, they were separated for the inspection of the transmission gear dog overlap. As suspected, the 2nd gear dogs were a bit rounded off where they were clashing against the adjacent gears and the overlap was minimal. This is not unexpected given the early production of the engine, as most are similarly found to be lacking in overlap.
As a bonus, the owner brought down two big plastic bins full of “extra” parts, including a couple of transmissions. I sifted through the transmission sets and found a nice 2nd gear, plus a NOS shift drum! The transmission gear cotters were removed so I could do the X swap in the gear ratios and the cotters that came out were offset ones! So, after some mix-matching of gears and cotters, the transmission should be in the best possible condition. I did replace the low gear bushing with one of the new reproduction pieces and the kickstarter pawl which was wobbling in the end of the shaft. The end bushing had some usual wear from the pawl rubbing up against it, so I decided to try to find a thin thrust washer to make a better surface for the kickstarter pawl to push up against. I found what seems to be a possible candidate with a Kawasaki washer that was ordered online.
The engine cases, cylinder head and associated covers were taken to a local engine rebuild shop for de-greasing. There was a lot of black goo inside the engine surfaces, partly from the camchain rubbing up against the seized roller when the engine was running. There was the usual gunk that covers the bottom of the cases, due to the use of original non-detergent oils, which were recommended by Honda in the early days.
The head was stripped of the cams, rockers and camsprocket before cleaning. The camsprocket weight springs were really loose so the ignition timing was all over the place when it was first started back up. The sprocket was sent to Tim Miller, in TX who specializes in building racing 250-305 engines and has come up with an effective rebuild for the sprockets, which lessens the total advance. This allows for the idle timing to be at 10 degrees BTDC instead of the usual 5 degrees, which Honda used. The added 5 degrees makes for a happier engine idle overall. New valves were ordered from DavidSilverSpares and the head was taken back to the machine shop for seat grinding to ensure full compression.
Little roadblocks…
Well, the nice NOS cylinders from Tim McDowell, which came with .50 MC pistons, turned out to still be on STD bore sizes, so with a fresh set of STD rings, I can reuse the OEM pistons and solve that problem. HOWEVER.. the NOS cylinders was a late-model die-cast unit, which uses the narrow 32mm tensioner that I didn’t have in stock, I had ordered the Capellini tensioner sprocket kit for use on the wide tensioner that came off of the stock cylinders. So, now I have to scrounge around for a usable narrow tensioner body and remove the old roller or Option 2 which is a NOS tensioner on eBay, but the tensioner doesn’t come with the spring and bar to push the roller out against the camchain. These parts are specific to the -020 tensioner assembly. Just when you think you have your ducks in a row……
Well, I did both.. bought the new tensioner and then discovered that I had a used one in the engine parts box after all. Problem solved.. or not?
The rebuilt cam sprocket came in and was carefully installed on the endless camchain. It’s a tricky proposition and required clamping the top end down with some sockets and nuts so I could join the two camshafts into the master spline of the sprocket. Once that was accomplished, it was time to install the camchain tensioner… and it wouldn’t fit into the back of the cylinders. Perhaps the Capellini parts are slightly wider than the originals, but it appeared that there was some casting flashing in and around the tensioner hole that was jamming the tensioner arm roller hardware. I tucked some shop towels into the opening and then carefully ground out the insides of the cylinder opening. It helped but still needed a bit of a push to clear the opening and finally fully install.
The cams and top-end bearings were all lubed up and the top cylinder head cover was installed. The top nuts were torqued down and only the oil pump installation is left after the engine is flipped over to expose the bottom end.
It takes over an hour to either remove or reinstall the engine assembly, given all the little bits to round back up and re-attach. I used a remote fuel bottle to connect to the carbs and with a half-dozen kicks the engine fired up and sounded pretty healthy. I had set the ignition timing statically just to get it running, but the project stalled until the requested Pro-Trigger electronic ignition system arrived from Florida. In the meantime, I noticed that when I rolled the bike around the massive 4.00x19 rear tire was making flat tire sounds. The tire is so large and so old that there are no date codes marked on the sidewalls. Checking air pressure, none was found. I aired-up the tire to 30 psi and shortly thereafter it went back to zero. I called my local shop to check on inner tube availability and thankfully they had one in stock. I removed the wheel assembly and hauled it down the eight miles to National City Motorcycles, where the owner, Rob, put it on his tire machine and replaced the tube and rim band.
After a few days, the ignition system arrived and was installed. It’s a bit fiddly because the trigger wheel with the magnets is just a round section of aluminum with no indexing to setup the correct timing. It’s a bit of trial and error, but eventually, the timing came in correctly and the bike was fired up once again. Winding down the final adjustments, the tank and seat were re-installed and the first test ride done, just around the block. Because the crossover tube fittings had been blocked off by the owner to reduce the fuel spilling when the tank was removed, the fuel supply to the petcock is somewhat limited to the right side of the tank. There seemed to be sufficient fuel in the tank, so a longer test ride was undertaken. The usual route is about a mile, down a long hill to a turnaround at the bottom.
I could feel it dropping a cylinder as I reached the bottom and finally it quit altogether. Rechecking the fuel supply on the petcock side and turning the petcock lever back and forth between On and Reserve, got it fired up again, but it only went about a quarter mile back up the hill before it quit again. I pulled the fuel lines off to the carburetor and nothing was coming out in reserve, but fuel did flow in the On position. The bike fired up again and I made it back home, avoiding the drama of calling a neighbor to come and fetch me, then returning with my truck and having to load up the bike for the ½ mile trek back to the house.
The bike was fitted with the yellow MotoBatt battery, which are generally very reliable. I noticed some corrosion build up on the terminals, which I hadn’t seen before on any of these batteries. Finally, I decided to check the voltage with a meter and the news was grim. 10V with the key off and 9v and dropping with the key On and the headlights On. When the bike was fired up again, the voltage continued it’s decline… the charging system was not working. I gingerly fished out the rectifier which was one of the later solid-state units, instead of the orange selenium units normally found on early bikes, but the test results were zero. It was a dead soldier.
I fished around and found one of the little cube full wave bridge rectifiers, that Radio Shack used to sell and with some connectors and extra wire, the unit was installed in place of the old rectifier. I had put the battery on the charger for an hour or so, which indicated 12+ volts at rest, so reinstalled it and started the bike up again. The voltmeter jumped up towards 13v, even at low speeds, so the electronic ignition was getting a full dose of juice as were the ignition coils. One more problem solved, but one more to go. Even after the battery was charged, the battery voltage dropped from 12 to 10 with the key On, so a new replacement was ordered.
I removed the gas tank and laid it on the left side so the fuel went to one side which allowed for removal of the petcock inspection. I was surprised to find that there was no brass tube fitted to allow for a normal ON fuel feed, before requiring the Reserve to finish draining the tank. Then, as I continued to inspect the petcock body, I realized that there was no reserve port function in the petcock body. If I had installed a brass tube into the petcock body, there would be fuel leftover as the level dropped and no way to finish using up the remaining fuel. This explained why there was no fuel flow in Reserve position as there is no way for fuel to exit the petcock. I removed the petcock body and probed the little fuel feed ports, finding some leftover debris and scale in the On port. So, with the understanding of what had been happening with the petcock and low voltage, I was getting more confident that the bike was okay, overall. However, the shifting issues were particularly troubling during the test rides. The petcock continues to perplex me, as I have never seen that before on a stock Honda petcock.
I had replaced the low gear bushing and re-shuffled the clutch pack to allow for clutch plate retention which was not possible before with the replacement clutch pack installed by the owner. I installed some of the offset cotters to help engage the gears, but had used some of the rare deep offset cotters, which were giving almost 90% gear dog engagement. In reflection, you can do too much of a good thing and the deep engagement may have been causing the gears to remain engaged rather than releasing easily when the next gear selection was chosen. Mulling it over in my head, the only sensible solution was to remove the engine once again, split the cases and re-do the transmission cotters. So, out it came again…
In the tear-down, I revisited the clutch plate stack and decided to replace the center hub with the later 5-plate version, which uses a thick Plate A and just one set of plates after that, using the retainer wires. This allowed the clutch plate set to more easily spin free at idle. Clutch drag at idle is a big cause of shifting problems, especially when finding neutral at a stop. These transmissions were designed in the late 1950s, so they can get caught up between gears, at times, if the shift selection isn’t done with some authority.
I replaced the .040” offset cotters with a set of the .020” versions, which reduced the gear dog overlap back towards 50-60%. There was some end play in the countershaft that causes the kickstarter pawl to get a bit cocked as the shaft moves in and out. I had ordered a 1mm thick thrust washer online that was a Kawasaki part and was able to insert it into the shaft next to the end bushing, which took up all of the end play without jamming the shaft up between the bearings. I sealed up the crankcases once again and reassembled the primary side with the updated clutch parts.
It was another hour of installation time ( 5 hours overall to R&R the engine and make repairs), but I was feeling more confident that the major problems were being addressed. Unfortunately, the right side carburetor started to drip from the overflow tube. The float was slowly sinking due to a pin hole so that was replaced. The drip continued once again and the float valve needle was replaced, finally stopping that leak issue. One final check of the spark plug caps turned up the left side with 17k ohms instead of the preferred 5k ohms. So, with that replaced, the bike started running better and better.
As you can imagine, lots and lots of labor time is involved in doing the basic overhaul work, then sorting out all the associated problems discovered in the repair process in these 60-year-old machines. People who work on these bikes begin to appreciate how many problems arise and the amount of time and effort it takes to make them return to their former glory.
Bill Silver
aka MrHonda
8/2024
No comments:
Post a Comment