A few months ago, my friend Bill M. contacted me about “rebuilding” a CL175K3 engine for a project that he was doing for one of his friends. The plan was for him to bring me the engine to rebuild and he would be restoring the chasssis then bringing that down here for the engine installation and then put all the bits and pieces back together again. The bike was purchased as a partially started project from a previous owner and the whole bike was disassembled.
The engine arrived with the lower end in a screwed-together wooden box, while the top end and carburetors were in separate bins. After about 15 minutes of undoing all of the wood screws, the bottom was revealed to have a damaged kickstarter shaft. A new one was provided, so this was obviously going to be a full teardown and repair. The engine was otherwise in decent condition internally, but required cylinder honing, valve seat repairs, vapor blasting and installation of the fresh parts. It was still on STD bore and the pistons were reused along with new rings.
Whoever started the project, was apparently new to the hobby, so virtually each and every single part was labeled with blue masking tape, including all of the wire connectors. So, part of the process was to peel off all of the blue tape from the components and clean the parts of the remaining adhesive.
The engine rebuild was mostly uneventful, apart from having to run around town, hauling the parts back and forth to my friend with the vapor blasting machine. A set of aftermarket carbs were brought along with the engine parts, but the originals seemed to be worthy of a good cleaning and kit installation.
Once the engine was completed, it sat for a couple of months while I was doing several other projects and waiting for Bill M. to finish the chassis and find time to marry the two project halves together. Finally, in Aug, fully four months later, the the chassis was delivered on an early morning trip from OC and work began. The engine was shoehorned into the frame and all of the engine bolts fed into their respective places. Bill had brought down a copy of the parts manual, so we could refresh ourselves about what went where and what might be missing. Slowly, on a very hot day, the bike began to take shape, rising like a Phoenix from the pile of parts emerging from their blue-taped packages.
The CL175K3 model is the only one that had a high-mounted front fender, which was composed of several various adapters to fit the bottom of the fork stem. According to some parts lists, the K3 was sold in 1969-70. The wiring harness was fed back into the frame recesses at the back of the chassis and the ignition switch mounted up on the forward bracket, beneath the gas tank on the left side. A charged lead-acid battery was pulled from its box and dropped into the battery box. These batteries have a vent tube that needs to be routed carefully, to prevent acid damage to the chassis during operation. I situated the battery so the vent was towards the rear of the battery box.
At first only the neutral light came on when the ignition switch was switched to the ON position. The bike had been supplied with a little aftermarket cube bridge rectifier in place of the OEM selenium unit which mounts on the inside of the frame behind the carburetors. When I touched the battery ground lead to the battery there was a strong arc, indicating some kind of short circuit. The only thing that is active when the key is OFF is the rectifier, so I assumed that it had a defect and we ordered a $100 OEM unit from an eBay seller.
In the meantime I was puzzling over the other electrical system issues, starting with the tail light function. Whenever a bike chassis is powdercoated or even painted, all of the ground paths need to be established again, as the powdercoat becomes an insulator to electrical circuit pathways. I had cleaned off the usual places for proper grounding but when I checked the power to the tail light, it showed power to and through the bulb, but my test light lit up only when it was grounded back to the battery. Studying a copy of the online wiring diagram didn’t show any separate ground path to the harness wires, except though the various components, but they were still mostly isolated from a good ground path. I finally eyed a single green female ground connector by the battery with no place to go. I made up a jumper wire and connected it to the female connector and grounded the other end where the turnsignal flasher mount bolts to the frame. Success! All the lights came on and power seemed to be restored to all of the lighting and other functions.
A few days later, the spendy orange rectifier arrived and was installed after removing the left side carburetor again. The mounting stud was well grounded and I was looking forward to completing the electrical system. But, as soon as I touched the two harness connectors together, there was a big flash and wires started getting melted! I quickly pulled the two connectors apart and reviewed the wire colors for each side. The harness side connector had the red hot wire across from the green ground wire, but these colors were swapped on the rectifier side. Obviously this was a dead short to ground for the battery feed line. I pushed the wire connectors out of the harness side to match the rectifier colors and plugged them back together again, gently. There was still some arcing going on, but less than before.
Finally, I thought to check the battery connections and finally noticed that the battery was installed BACKWARDS! This was the cause of all of the electrical arcing from the rectifiers, both the aftermarket one and the OEM version. MrHonda had a senior moment and hadn’t paid attention to the battery polarity. The battery was installed with the markings turned away from me and I was using the position of the battery vent tube as the indicator of the orientation of the battery when mounted in the frame. It all became clear in an instant and now the damaged rectifier needed to be removed and replaced again. In looking at the rectifier, only the green ground wire that comes from the connector to the side of the rectifier mount was fried, so the rectifier through bolt was carefully removed, and a new wire with a ring terminal was installed. With everything re-attached, there was no arcing when the battery was re-connected and all of the rest of the electrical functions were operating normally.
In order for the Scrambler exhaust system to be installed, the left side air filter must be attached to the carb and then the left side cover snapped into place. Then, the wiggly Scrambler exhaust pipes can be hooked back into the exhaust ports and attached at the rear mount. That done, the bike was rolled off the work table and down to the driveway where the fuel tank was waiting to be installed.
The petcock appeared to be an aftermarket piece, already connected to fresh hoses and inline filters. The petcock mounting bolt was missing the sealing washer, so I had to dig up one from my pile of leftover carburetor parts. Then the screw wouldn’t go into the tank without chasing the threads with a 6mmtap. Once everything was put together, some fuel was poured into the tank and the moment of excitement arrives. The original kickstarter which had flattened out splines was replaced with an aftermarket piece which was an inch shorter than the OEM unit. This made kickstarting a bit of a chore as it was near the rear footpeg. I had already checked the ignition timing, so it should have fired up quickly. After a dozen kicks it coughed to life reluctantly, then stalled out. I looked down to see gasoline dripping down from the left side of the engine and oil dripping down on the right side of the engine. Now what!!!!!?!?!??!
The left side carburetor was dripping from the overflow tube and even with the petcock turned to the OFF position, there was still a persistent leak. The right side leak was from the oil filter cover, which had been sealed up with new o-rings, but continued to leak after several inspections and measuring the o-rings for the proper sizes. I happened to have a spare outer o-ring so stacked two on that side and the oil leak ceased. I tried to access the left side carburetor float bowl to see if something was obviously evident, perhaps with a failing float from a pinhole. It always seems that if you are working on a Scrambler of any size the left side carburetor is the one that will have an issue.
The exhaust port gaskets were supplied from an ancient gasket kit and consisted of some asbestos wrapped with copper wire. These compress down to nothing when installed, and the result was exhaust leaks at the flanges. The pipe packing that seals the two exhaust pipes together at the rear junction was mostly gone, so there as a leak back there, as well. So, the tank came back off so the petcock could be rechecked for the dripping issue and the exhaust removed again for new seals. With the exhaust removed the carburetors could be reinspected again. The left side drips had stopped, but when the engine was running briefly, it sounded like it was running rich on the right side, which was confirmed by a black plug when removed for a compression check,
New parts were ordered and the bike’s carburetors removed and checked again. There were aftermarket kit parts installed and they are often not to OEM specifications.
In the meantime, more electrical work was required to reconnect all of the wires inside the headlight shell. The rubberized instrument lights that pushed up inside holes in the back of the speedometer and tachometer were mostly all toast. A previous person had wrapped a lot of black electrical tape around the bulb sockets in an attempt to keep them situated in the lighting holes, but obviously, this was a failed attempt. I happened to have a string of instrument light wiring from a different model, but all of the socket rubbers were in great shape. I snipped here and there, finally getting them all spliced in for functioning instrument lighting. I had to special order the 12v 3w light bulbs to fill all the empty holes.
When I went to fit the headlight assembly back on, the left-right adjustment screw and bracket were broken away from the back of the reflector. When the rim was test-fitted to the headlight shell, it became obvious that the shell, which is metal, was out of round and painted that way along with the other metal parts (plastic side covers) on the bike.
I had some various woodworking clamps hanging in the shop and one was big enough to reach around the perimeter of the shell and with some strong twists of the clamp, brought the shell back to a circle once again, without damaging the painted surface. The left side headlight bracket had a bend in it, which needed straightening. The bike had surely been crashed at some point and the damage was left unattended by the painter and previous owner. Finally, all the lights started to function, but the headlight assembly isn’t centered with the midline of the front wheel, so more work needs to be done there.
The bike was run on and off my work table, to the driveway near the garage door opening for follow-up work on the fuel system. Repeated removal, inspection, cleaning, adjusting and re-installing of the carburetors failed to remedy the fuel fouling of the spark plugs. A more detailed examination of the associated components in the ignition and fuel systems didn’t give a solid clue as to the cause of the carburetor problem. It was finally resolved when a comparison of the needles, slides and idle jets revealed that the aftermarket parts were not a perfect match to the OEM parts.
See the next story on CL175 troubleshooting for how the process was performed and how it was finally resolved after hours of trial and error, including the replacement of the stock carbs with some Chinese copies. 2024 has brought in very difficult project bikes to sort out and rebuild to specs. It ain’t easy being MrHonda sometimes.
Bill Silver
www.vintagehonda.com
8/2024
The bike is actually a 1969 CL175K3!
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