Monday, July 18, 2022

Burning carbs on the CB550 Honda

Of all the vintage Hondas I have worked on, the carburetor removals on the CB500-550s are about the worst to accomplish in a reasonable amount of time. Of course, on the heels of the CB360T trauma, the owner serves up a 1975 CB550 with 14k miles on it, which is barely running, and wants it sorted out for sale this summer. The bike was faded, dirty, and missing the centerstand. The rear tire was oversized and there was no license plate mounted on the tail light bracket.

The first problem was that the front brake was dragging. I had cleaned out the caliper when I visited the owner’s house, about 25 miles away, a few weeks back. That seemed to have improved the situation, but after getting the bike pushed into my truck for the trip home, getting it back off the truck was a challenge. I loosened the caliper mounting bolts enough to get the brake freed up so I could get it safely off the truck and up into the service rack. Knowing that the caliper was already cleaned up, the issue probably resided in the master cylinder. The little bleed hole appeared to be restricted or mostly plugged up, which causes the brake pressure to remain constant, instead of relaxing when the lever is released.

There was a big scuff mark on the top of the master cylinder cap from a small crash, so it was cost-effective to just order a replacement from and be done with it. Once it was installed and bled the brake function was restored to normal. One down and more to go…

The next big problem was that the ignition key was not a match to the seat lock! The switch had been replaced with an OEM Honda unit with a 21H key number vs. the T2979 lock for the fork and seat. I spent 15 minutes reaching underneath the seat to remove the seat hinge pins, which allows the seat to be loosened up enough to get to the two nuts that hold the seat latch pin loose. The seat can be removed but then you have to take the latch off the frame with the two Phillips screws. One of the screws came out with the impact driver and the other one was in so tight that I had to drill the head off to get it loose.

Removing the carburetors was next and that is never a fun experience judging from my past dealings with 500-550s. The clutch cable dives down between the carburetor bodies on the 550s, as well as a vent tube that also makes its way between carb 3 and 4. Early 500 Fours had a different clutch release system and the cable doesn’t interfere with the carburetors.

The battery was removed and charged, followed by the removal of the rest of the battery box, the air filter housing, then the extraction of the air box behind the carburetors. Honda wrapped the frame around the airbox and there is virtually no room for the carbs to come off of the manifolds to pull them off the bike. After a lot of wrestling and pulling, I was able to remove the carbs from between the head and the airbox. Usually, you can figure out how to disassemble these things, but on the installation, I discovered that removing the clutch cable mount at the back of the engine gives much-needed room to maneuver the air box in and out of the bike. Still having to disassemble half of the bike to get the carbs on and off is not a fun way to spend your time.

Once off, the carbs were in relatively good condition inside, but I replaced the internals with kit parts and replaced the intake manifolds with a fresh set. The biggest problem with the carburetors was that the welsh plugs located at the outsides of the 1 and 4 carburetors were missing! These are not separately available parts from Honda and online searches for a 1/2” (13mm) plug came up dry for the most part. Apparently, there were plugs like that for some lawn equipment carburetors that might work, but most listings didn’t show sizes. I had a full set of used carburetors that wound up being parts donors just for those two little plugs.

I discovered new electronic ignition systems on eBay, obviously from China, as they were $69 vs. the $150+ Dyna kits. I ordered up a kit, which came quickly, but without any instructions which could be a problem for novices. Fishing the old point plate leads out from the little clamps under the engine and then up next to the air box takes a bit of time and patience but it is mostly plugged and play. I put the rotor trigger on backward which lead to a no-start condition until I switched it back 180 degrees.

I had already adjusted the valves and camchain, replaced the spark plugs, and wound up putting on new replacement coils, as the old wires were hardened and had been shortened before to keep good connections.

So, initially, it fired up sounding decent, but the idle was erratic. I was feeding it with a remote fuel bottle so I could make adjustments to the carburetors for synchronization. The engine compression readings were 180, 150, 145, and 170 psi, so you can’t expect really even readings with variable compression issues within the engine.

I had cleaned out the petcock screen and disassembled the petcock to check for any issues, which were not a problem. Adding fresh fuel to the tank, I reassembled the tank and seat, then took it out for a short run around the block. I set out for a longer run, which went okay until I was a mile away then it died. I had only put about 1.5 gallons of gas in it, so switched to Reserve and it started back up again. On the return, it ran well up through the revs, but at the top of the hill, it started to falter again. I kept the revs up enough to get it back to the garage, but it sounded like it was only running on 2 cylinders, plus it started peeing oil off the left side of the engine beneath the countershaft cover.

These engines seem to suffer from flattened o-rings that create oil leaks into the little chamber of the countershaft cover. Other common oil leaks come from defective oil pressure switches and there is also a very large diameter o-ring that surrounds the oil pump where it bolts to the body. After replacing the o-rings on the pump, and test riding it again, the oil drops kept dripping when the bike was on the side-stand. That usually only means one thing… the shift shaft seal is leaking. So, off the cover comes again (the first time required drilling out one of the screws) and confirming the leak at the seal. I don’t usually stock parts for 500-550s, so it was back to eBay for a $10 seal and to wait some more. It took 4 days for a small seal to come from 100 miles away and the part number on it wasn’t a match for what was listed on the auction page or parts lists, but apparently, Honda superseded the part number and the older seal is the same dimension as the upgraded one. One more problem solved.

In the meantime, I noticed a little gasoline drip from the petcock lever, so drained out 4 gallons of gas that I had just put in and removed the tank to check the petcock parts again. There is only one little o-ring that can cause a leak on this style petcock, so I thought that this might be the cause of the leak.

I noticed that there was a special flat washer on the edge of the workbench that seemed familiar, so when the petcock came apart again, I discovered that it had been left off of the reassembly last time. More senior moments…

BUT, as I was draining the gas tank for the petcock check I lifted the gas cap and heard a little swooshing sound as if there was a vacuum being created by the exiting fuel flow. I had just put a new aftermarket gas cap on the tank after seeing the disaster cap on the CB360 that was here previously. What I noticed was that the little v-shaped vent hole on the cap showed some kind of white material that seemed to be blocking the hole. The cap pieces are held together with a small screw, so I unscrewed the cap assembly and found a tiny piece of what looked like cotton that was sitting over the vent hole. I can’t determine if all of these caps are made the same with little cotton balls inside, perhaps to soak up any gasoline splash inside the tank, but I wasn’t leaving it in there. A good 15-minute test run revealed no fueling problems as had happened before. All the header pipes were at the same temperature using the laser temp meter, so removing the cotton ball seems to have resolved the stumbling and stalling condition.

With the petcock reworked and the fuel tank installed, I filled the tank back up again. Rode the bike again with good results overall. I aired the tires up to specs and thought the end was in sight, but then checked the date codes, which ended in 00 and 02, so new tires, tubes, and rim bands were ordered.

While checking the electrical system out, I discovered that this was one of the bikes that Honda had put the infamous beeper on the turn signal system. The signals wouldn’t flash at idle and the beeper made a horrible sound, so it was disconnected. The flasher unit, which was an original Signal Stat 142 unit, which apparently is no longer in production. These are the tiny rectangular flashers the size of two sugar cubes with a little rubber mount that clips the unit to a bracket on the electrical panel. Fortunately, the people at offers an aftermarket unit for about $12, so that went on the order list. The flasher came in promptly and the turn signals are working fine now.

I initially checked around for a centerstand and the mounting hardware, but nothing came up and I got no responses from the Facebook forums that I am subscribed to for vintage Honda bikes and parts. I fed the part number and description to the owner, who miraculously found one that was incorrectly identified on eBay as a Super Sport part (different than the K models). It was purchased and shipped to me for installation. This became another time-consuming and frustrating repair process as one of the exhaust pipes had to be removed to access the frame mounting points in order to push the pivot shaft into the frame mounts and the stand tubing.

The stand was fitted up okay, but then the challenge to try to reconnect the return spring reared its ugly head. With the exhaust pipes in the way on the right side, the access to the end of the spring and the hook on the stand was restricted. I tried all kinds of tricks to try to get the spring connected and even went to the auto parts store and bought a brake spring tool, which was cheaply made in China and didn’t really work in this kind of application even when some extended tubing was used to gain more leverage on the spring end. Finally, I found a thick 5/8” lock washer and used it to bridge the gap successfully. Not pretty or factory approved, but it works perfectly fine, but I spent more than a half hour of my time, wrestling the parts back in place. It’s so much easier to change the rear tire when you have a centerstand to prop up the bike!

The left side dyno cover badge was scrubbed off on a right side tip-over and the replacement parts are in the $100 range, plus the three little clips that are $6-10 each (3 required), so I thought I better check with the owner before putting that shiny piece on an otherwise dull-looking daily driver bike. The reply was a thumbs down on that question.

The bike did get an oil and filter change on top of everything else, so at some point, it will be sent back home with a full service and hopefully regular use at the beach this summer. With fresh rubber and a brake upgrade, it can resume being actively ridden again after probably a 15-year sleep.


  Bill Silver aka MrHonda


Friday, July 8, 2022

CB360T A bike of a thousand problems…

At first glance, the 1975 CB360T seemed to be a fairly solid bike

Image courtesy of AHMC

but ran poorly when the owner started it up. The tags on the out-of-state plate were from 1984 and it showed about 11k miles on the odometer. After a battery charge, the owner started it up, but it would barely run enough to go 100 feet down the driveway and back. This should have been a fairly straightforward repair job, but of course, it wasn’t.

One of his first problems was that the petcock was an aftermarket version and the lever positions are backward from OEM Honda parts. So, with little fuel in the tank, putting it on what is normally RESERVE was actually turning the fuel OFF.

On the service rack, it was obvious that some kind of crash had occurred as the tachometer was an all-plastic version used on the early CB350s. The right side mirror was missing, but fortunately, the mirror mounts were all intact.

The air cleaner system is kind of a Jenga mashup with little screened extensions on the tops of the air filter housings, which are held together with a long bolt, plus two more attaching bolts along the top edges. The filters share a central through-passage, which increases the air filter total volume and reduces intake noise in the process. Dismantling the filters leads to the removal of the carb rack, which is controlled by a push-pull set of throttle cables, which are not easily accessible to remove and install.

With carbs off and bowls removed, it appeared that most of the jets were OEM, but the float valves were probably aftermarket. With some of the jet edges rounded off, it was clear that someone had been in there once or twice before. There was some scale in the jets and passages, but they didn’t look that bad overall. I had ordered an inexpensive carb repair kit online from a reseller of Chinese-made kit parts and soon discovered big problems with their kit parts. They included two sizes of main jets, which covered a couple of versions of the CB360 calibrations. Unfortunately, the jets were not marked as to what size they were. I have tapered reamers to clean jets out with and used them to gauge which ones were which as they slid along the reamer surfaces. The jets didn’t seem to be the same size as the OEM jets that were still in the jet holders, however. I sifted through my piles of misc jets to see if I could find other OEM jets to compare these with and came up with mixed readings.

The idle/pilot jets were a completely different problem, however. As they were screwed into the carb body, they tightened up before the threads were fully engaged and when you tried to back them out, there was squeaking and they got harder and harder to remove. Then the slot on top wore down so they became embedded into the body causing a huge problem. Using a combination of left-hand drill bits and 3mm metric taps I eventually was able to remove them and put the OEM-used jets back in place.

The next problem was that the float bowl gaskets were entirely too small for these bowls. I contacted the eBay seller outlining the problems and they offered a refund for the parts, but I still had to order a separate set of bowl gaskets to close the carbs up. I put the carbs back onto the engine and fed them with a remote bottle, to see how it sounded. And it ran horribly…

I had already replaced the points, condenser, and spark plugs with an old OEM tune-up kit so was confident that those parts were not part of the problem. I also adjusted the valves and timing chain. These engines had a recall for damage to the tensioners, but there was no sign that this engine had been done, however, there was no evidence of a broken tensioner. The oil came out dirty, but nothing in the way of damaged metal parts was evident.

I removed the carbs again and carefully checked them over, then discovered that my inspection of the carb diaphragms missed the fact that there were tiny pinholes in the rubber diaphragms. I ordered a set of replacements from which came in 2 days. With new diaphragms installed the bike began to sound much crisper but it would take turns not idling well on one side or the other as it warmed up. The coils were some kind of aftermarket replacements, but whoever installed the spark plug caps onto the wire end kind of missed the center of the wire core, so the spike inside the cap was running parallel to the actual wire strands, probably arcing across the little barrier. The more I worked on the carbs and other subtle problems, the better it ran, but it took about 4 attempts of pulling the carbs on and off to get it to run properly.

The fork seals were leaking slightly, so new seals and dust covers were ordered up. The forks come off easily, but the bottom damper bolts were very tight, which slowed the disassembly process down until I put an air wrench on them. When I drained the forks I noticed that one of the drain bolts was not a 10mm bolt head size. Probably SAE instead! In the end, both drain bolt threads were damaged from a previous repair attempt, so I had to put a Heli-Coil insert into both sides with a sealing washer to prevent leaks. For some reason, the fork seals were very difficult to remove. I had to use a Dremel cutoff wheel on one of them to get it loosened up for removal. While attending to the forks and front brake caliper earlier I noticed that the date code on the front tire was from 1986! The owner agreed that a new set of tires was in order.

Finding tires for vintage Hondas seems to have gotten quite challenging recently. I guess the global supply chain issues are hitting all industries. In this case, the owner ordered a set of correct-sized tires from Amazon. What showed up was some Chinese-made K70 tread pattern rubber. He had ordered tubes and rim bands, but the tubes were back-ordered. Fortunately, I happened to have a set of new tubes on hand, so that little delay was averted.

The front disc brake had a soft feeling as if there was air in the system, as it would improve if you pumped the lever a few times. I rebuilt the master cylinder and caliper, bled out all of the air, but the soft lever feel persisted. All that is left are the flex lines, which of course are almost 50 years old. I wrapped a bunji cord around the brake lever overnight to see if would force any trapped air from the system. The next morning the brake system felt the same, so new hoses were ordered/

The drive chain was worn out, of course. It was the factory-installed endless chain that Honda was putting on bikes back then. I had a spare chain in stock, so averted ordering another one. I have noticed that local motorcycle shops don’t even stock anything except o-ring chains for $100+ prices. Any plain roller chains have to be ordered.

More little issues arose, like the three speedometer light bulbs were all blown out and the headlight bulb was working but the seal between the glass lens and reflector had deteriorated, so the lens was rotating around inside the reflector as the chassis vibration affected the bulb. A layer of GOOP solved that problem.

The handgrips were those original ridged OEM items that are hand-killers after 10 minutes of riding. Honda used them on many bikes during that time and they are truly a horrible choice. I ordered the smoother OEM Honda replacement grips and installed them easily.

When the seat was flipped open, I noticed lots of battery acid damage around the battery area, including the nearby starter solenoid. Someone had failed to keep a drain tube on the battery and acid splashed all over the battery box and surrounding chassis parts. The battery box unbolts from the frame, so was treated to some rust neutralizing spray and a coat of black paint. The list of little tasks seemed endless as they were dealt with one by one, but finally, the bike was ready for a road test. I had forgotten how nice it was to have a 6-speed transmission behind a vertical twin like this. The engine makes impressive power and keeping on the boil was easy when you have all those gears to play with while riding. Fortunately, the clutch function was intact and I avoided having to pull the clutch cover to unstick the clutch plates.

The run of the 360s, which replaced the long-standing 350 twins, was only for a few years. With so many bikes on the market at the time, including the lovely CB400F, the 360s never really caught on with the public. Honda made a Scrambler version for just a year and a CJ360 cafe-style bike that was pared down with the removal of the electric starter, disc brake, and centerstand. That model featured a 2:1 exhaust system, as well. Honda tried their best to keep that series alive but eventually replaced them with the new CB400T twins with 3 valve heads and electronic ignition systems.

The bike was returned to the owner, who swapped out the 360 for a CB550 in similar condition with similar sets of problems which will be the subject for the next story.

Bill Silver aka MrHonda 7-2022