Finding functional parts for 50+-year-old Hondas has become ever so difficult as the years go on. Simple parts like points, condensers, rectifiers, and fuel system components are all long gone from Honda’s warehouses and dealerships.
Aftermarket parts have a rather poor reputation for quality and accuracy. While most of the replacement parts come from SE Asia (Thailand, Taiwan, Vietnam, Hong Kong) more and more are being filtered in from Chinese companies who try their best to copy the original OEM parts but don’t quite have it right in many cases.
The current example brought to me was a tidy CB160, which had some restoration work and was showing low miles on the odometer. The overall look was very presentable, including nice OEM mufflers on both sides and a set of Hedenau tires on both ends. The owner had seen my name on various forums and noticed that I was in the San Diego area. He lived in Escondido, which is about 40 miles north of Spring Valley, and contacted me to see about getting his “carburetors” rebuilt.
Having just cleared out a set of CL77 and CB77 bikes from an owner who also lives about the same distance away, just in a different direction, I was able to take the CB160 in for some needed repairs.
The owner brought it down in a U-Haul motorcycle trailer, hauled by his late model Ford Crew Cab truck. The bike looked very nice at a distance, but as we removed it from the trailer I noticed something that was definitely out of the ordinary… The carburetors were Chinese copies of the early Power-Jet CB/CL175s from the 1967-69 era. The owner had purchased carb kits for a “CB160” in hopes that they would be useful for the repairs. The petcock had an additional shut-off valve plumbed into the fuel delivery system, all of which was done cleanly, but eventually not necessary.
The previous owner stated that he had tried to repair the petcock and it kept leaking, thus the installation of an additional shut-off valve. Apparently, the petcock leaked into a carburetor, which filled up and flushed fuel down the intake port and into the crankcase. Rather than just flushing the gasoline out with a couple of oil changes, he decided to rebuild the whole engine! Once completed, it went up on BAT (bringatrailer.com) for sale. And now it was in San Diego with a worried new owner.
So, the first order of business was to see if it would start, giving me a few clues about what the issues were. The nice hot battery kicked the engine over but with a skip and clank sound due to the starter clutch springs being worn down. The bike had been sitting for a few months, so I surmised that the fuel had gone off and the idle jets were plugged.
After removing the side covers, air filters, and carburetor set, the carbs were disassembled and inspected. Sure enough, the idle jets were blocked. What I have seen consistently is that the Chinese carburetor manufacturers fairly accurately copy the original Keihin designs but take some liberties with some of the components and also completely fail to mark any of the jets or needles with any kind of calibration clues. So, with basic cleaning and unplugging the idle jets, I checked the float level settings against the Honda tune-up book. There are two different float level settings for the 160 carbs but only one for the 175… 21mm. When I went to measure the float height, they seemed to be about 21mm but the flange where the gasket sits was raised up a couple of millimeters, so if you measured at the gasket surface area, the reading would have been more like 24mm. Both carbs were the same, so I left them as manufactured and waited to see how the engine would perform. The carb slide needles were also unmarked, but the clips were set at the #2 slot. The owner complained about the engine not taking the throttle cleanly, so I moved the clips down to the #4 slot and reassembled everything after changing out the o-rings and bowl gaskets.
This brings up another annoyance… The width of the bowl gaskets is usually too wide and the front section hits the two little posts that are supposed to keep the gasket from pushing inwards when the bowl is attached. What happens is that the gasket starts to flip upwards until it is compressed by the edge of the float bowl. I have started using a small hand-held punch to notch the gaskets where they are supposed to ride up against the posts, to help keep the gasket flat in the track.
The other issue, at least for CA owners is that all the pump gas has 10% alcohol which causes the rubber bowl gaskets to expand and distort when exposed to these fuels. Often, when you remove the float bowl to service a jet or check the float level, the gasket expands out beyond the original size and it will NOT go back into place. It has become necessary to keep extra gaskets on hand to use when the originals cannot be installed again. Fortunately, some of the gasket makers are now using materials that are alcohol-resistant but they still make the widths excessively wide in most cases.
The carburetors continued the dance, each doing different things. One would leak past the bowl gasket in front. The edges of the bowls were machined off with something rough so there were a series of gouges in the edges. I filed them down as much as possible and finally, the gasket stopped leaking. Then the other one started overflowing. The floats are plastic and I was concerned that one might have leaked internally. I finally used the float valve from the kit, which uses a different type of needle, but it worked and the fuel stayed inside for both sides, finally.
The petcock problem was that it was dripping with the lever in the OFF position. I drained the tank through one of the fuel lines and then pulled the lever plate off with the 2 screws. The 4-hole gasket was in poor condition and the back side of the lever was cupped at the edges. I smoothed out the lever face, installed a new petcock gasket, and buttoned it back up. When I added the ½ gallon of gas back in, the petcock started dripping again! I drained the tank again and rounded up the parts from the supplied petcock kit to remove it and determine what was happening. With the bowl off, the screen, and the o-ring removed, I put a screwdriver on the first screw and it was loose! Even though the previous attempt at kitting up the petcock failed, the actual reason was that the screws were not tightened securely and the gasoline was draining past the screw threads and filling up the bowl directly, bypassing the fuel valve.
I replaced the aluminum screws with some fiber washers from the repair kit that came with the bike and suddenly there are NO drips from the petcock now. Problem solved and all the extra plumbing and shutoff valve stuff was discarded for a couple of nice chunks of Honda 5.5 fuel line of matching lengths. This brings up another subject…
Any of the vintage bikes with dual carburetors can be subject to fuel starvation on one carburetor, even when the petcock is clean and the float valves are working normally. What seems to happen is that the fuel flows to the easiest pathway and air seems to be trapped on the opposite side fuel line. Some people have tried blowing into the gas cap opening to pressurize the fuel lines which sometimes works, but is NOT a recommended practice. What I have suggested to others and what I have found is if you use matching lengths of fuel hose to each carburetor, the problem disappears. At least that has been my experience to date.
So the next round of repairs was to address the slipping starter clutch. I had forgotten that the little twins use a 15mm release bolt instead of the commonly used 16mm size. I dug through my selection of axles and found one that worked perfectly. Once the rotor was removed, all of the rollers were still in place with some spring pressure, but when they were all removed, the lengths were just under one inch and the new ones were about an inch and an eighth. Doesn’t seem like it should matter much, but it usually does fix the problem. Getting the rotor back in place was a bit tricky with the side cover still in place. I lined up the crankshaft locating pin with the rotor and held the rotor squarely on the end while I reached over and turned the crankshaft with the kickstarter arm. It took a couple of tries but you can generally nudge them back in place without removing the whole surrounding cover. The starter function was much improved, but it still had a little bit of slip, probably due to some glazing on the starter clutch hub surface.
After all of this work, the engine spun over with the electric starter, but wouldn’t fire up. I pulled the plugs and they were fuel-fouled, so I connected a fresh pair to the plug wires and looked for spark. It didn’t seem to be present. Off with the point cover and when I arced across the open points, the plugs fired, but not when it was spinning over with the starter. The aftermarket points seemed to have been corroded over which failed to allow them to close correctly, so there was no current flow through them to energize the coil windings. A bit of scrubbing with a Dremel cutoff wheel disc and some contact cleaner and we had spark once again. I checked the ignition timing and it was right on the F mark, so it was good to go.
The bike fired up on full choke but didn’t want to run with anything less than it full on for about a minute. These carbs do have the little spring-loaded flappers which prevent over-choking the engine. After a minute or so of choking, it finally took throttle correctly. I’m sure that the needle clip position had a lot to do with early running issues, as the primary problem.
Then, there was a problem with the oil change… The 160 engines have TWO drain plugs underneath and the forward one had a 14mm head bolt instead of a typical 17mm bolt head. When it was removed, the “drain bolt” turned out to be a shift drum locating pin with the roller still attached! I had to check the existing one to be sure that someone hadn’t accidentally switched places, but it was correct, so I guess the forward drain bolt was lost and the owner just used whatever fit in its place. I do get the weird ones lately.
I had to air up the tires from 15psi to 30psi before a test ride around the block and down my little testing route. The bike pulled third gear up to 50 mph on my uphill road section and sounded great.
I called the owner and said “Come get it” and he happily came back down and loaded it up after a bit of a test run himself to see how my work had transformed the reluctant starter machine into a fully functional one, once again. After all was said and done, he mentioned that he might sell it because after fulfilling his childhood memories of owning one, back in the 1960s, it was now really too small and under-powered for general use. I hear that a lot from owners who want to relive the past for a moment, but then the reality of regular use sets in.
So, now back to the current CL77 project, which arrived in the back of a mini-van, mostly in pieces.
Bill Silver aka MrHonda
01/2024
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