1972 CB175: rebuild then restore

ancientdad said:
Unless the main harness got pulled and it affected some connections inside the headlight case where all those relevant connections are from the right handlebar switch.
Click to expand...

How would I go about testing those connections? I decided to focus on troubleshooting the headlight first. I used a test light and checked for power to the high (dark blue wire) and low beam (white wire) inside the headlight. When the switch was turned to those positions the test light would turn on. I also checked that the bulb is good by removing the light and attaching the ground (green wire) to the negative terminal of the battery and the blue and white wires to the positive. The light bulb seems to be good. Any ideas?
 
carteredward4 said:
How would I go about testing those connections? I decided to focus on troubleshooting the headlight first. I used a test light and checked for power to the high (dark blue wire) and low beam (white wire) inside the headlight. When the switch was turned to those positions the test light would turn on. I also checked that the bulb is good by removing the light and attaching the ground (green wire) to the negative terminal of the battery and the blue and white wires to the positive. The light bulb seems to be good. Any ideas?
Click to expand...
Everything in the headlight case is powered by solid black wires that are hot when the ignition switch is turned on, including the handlebar switches. If the turn signal flasher got bumped and disconnected that would explain the turn signals, but not the headlight or taillight. Check that all the green ground wires are also properly connected inside the headlight case, and if neither of those are it then pictures of the wiring inside the headlight case as well as under the tank would help, and you should also refer to the wiring diagram as well.

Edit: while most everything is powered by 12v switched from the black wires in the harness, I neglected to mention the headlight circuit is powered by the brown/white wire off the ignition switch so check that one for power with the key on as well. The ignition switch plugs on earlier models were round, brown connectors that often became disconnected if bumped.
 
Last edited:
ancientdad said:
Everything in the headlight case is powered by solid black wires that are hot when the ignition switch is turned on, including the handlebar switches. If the turn signal flasher got bumped and disconnected that would explain the turn signals, but not the headlight or taillight. Check that all the green ground wires are also properly connected inside the headlight case, and if neither of those are it then pictures of the wiring inside the headlight case as well as under the tank would help, and you should also refer to the wiring diagram as well.

Edit: while most everything is powered by 12v switched from the black wires in the harness, I neglected to mention the headlight circuit is powered by the brown/white wire off the ignition switch so check that one for power with the key on as well. The ignition switch plugs on earlier models were round, brown connectors that often became disconnected if bumped.
Click to expand...
Thanks for the help! I'll inspect it a bit more tomorrow
 
carteredward4 said:
Thanks for the help! I'll inspect it a bit more tomorrow
Click to expand...
Well on further inspection and reviewing some YouTube tutorials, I realized I missed a grounding wire connection at the rear of the motorcycle. Now all my electronics seem to work. Thanks for your help in troubleshooting. Took me a while to inspect everything in the headlight but it all looked good so I turned my attention rearward.

The only issue I have with the bike currently is oil leaking from the left side of the engine crank case. Most of the oil seems to be leaking out of bolt 22 and 19 from the diagram below. I'm guessing the oil isn't actually coming out of the area around bolt 19 but it might be pooling there a bit before draining out. It appears like the left crankcase cover can come off without removing the engine from the frame. Is that possible? I think it is necessary for me to replace that gasket or else I will just be leaking oil everywhere. Also, any preferred vendors for gaskets?
1749828938007.png
 
Glad it turned out to be something simple like a ground. Yes, the left crankcase cover can be removed in the frame. You'll want to use a little Hondabond around the alternator wiring grommet when you put the cover back on, they get hard with age and will not seal without a little help. You might just invest in a bottom end gasket set, buying one gasket can often be half the cost of all of them and at some point you might need to go into the right crankcase cover. Not likely leaking from that bolt or screw itself, but something behind it (clutch rod seal) could be the source. You should replace the clutch rod seal while you're there too, and use a thin layer of Hondabond on the outside circumference of the seal when you replace it as well.
 
Thanks! I think you are right about ordering the full gasket kit. Do you have a preferred source for those kits and the clutch rod seal? Looks like they are available on those guys in Houston for a reasonable price. Is that the best source or is there a better one?
 
carteredward4 said:
Thanks! I think you are right about ordering the full gasket kit. Do you have a preferred source for those kits and the clutch rod seal? Looks like they are available on those guys in Houston for a reasonable price. Is that the best source or is there a better one?
Click to expand...
For whatever reason, the selection of available gaskets and seals for the 175 engine are fewer than other vintage Hondas but based on price, anyone is usually less expensive than those guys in Houston. This gasket set from 4into1 has a few less pieces but is $12 less and might get free shipping (after January 1, 2025 4into1 allegedly offers free shipping to the CONUS), and it has what you need. You might invest in a set of seals if you plan to keep the bike as other small ones might start leaking, like the kickstart or shift shaft seals.

4into1.com

Engine Gasket Set - Honda CB175 CD175 CL175 SL175 - 1968-1973

Engine gasket set for the Honda 175's. If you're doing an engine rebuild this is a great set to have on hand.
4into1.com 4into1.com

Here's a seal set for barely over half the price of those guys in Houston

www.disastermotors.com

Honda CB175 CL175 CD175 SL175 Engine Oil Seal Kit Kick Start, Clutch, Sprocket, Shift Seal

This is a brand new complete engine OIL SEAL KIT for the now vintage Honda 175 twins These seals are the ones you need if you have a 1968 1969, 1970, 1971, 1972, 1973 CB175, or 1968, 1969 1970, 1971, 1972, 1973, CL 175 Scrambler . These are also for correct for the CD175 and the SL175 Motosport...
www.disastermotors.com www.disastermotors.com
 
New problem to fix. The left carb seems to be flooding which is resulting in no or very intermittent ignition in the left cylinder. I pulled the carb and checked the float and needle. Both seemed to be fine. There is so much gas in the carb that it begins to leak. Going to pull it again and double check everything but if there is anything in particular I should look for, any advice would be much appreciated.
 
carteredward4 said:
New problem to fix. The left carb seems to be flooding which is resulting in no or very intermittent ignition in the left cylinder. I pulled the carb and checked the float and needle. Both seemed to be fine. There is so much gas in the carb that it begins to leak. Going to pull it again and double check everything but if there is anything in particular I should look for, any advice would be much appreciated.
Click to expand...
Check the float to see if it has fuel inside it, sometimes the solder seams on them allow fuel leakage into them and then they won't float fully.
 
ancientdad said:
Check the float to see if it has fuel inside it, sometimes the solder seams on them allow fuel leakage into them and then they won't float fully.
Click to expand...

After pulling the carb giving it a thorough cleaning and checking the float, I found no issues. While I was doing more troubleshooting, I noticed my spark plug boots was touching the points cover and sparking on the cover. I'm not entirely sure but I think that was causing the spark to not actually ignite the fuel. After removing the spark plug, thoroughly cleaning it and fixing the spark plug boots and wire, the engine seems to be firing correctly now. Would that make sense or did I just get lucky?
 
carteredward4 said:
After pulling the carb giving it a thorough cleaning and checking the float, I found no issues. While I was doing more troubleshooting, I noticed my spark plug boots was touching the points cover and sparking on the cover. I'm not entirely sure but I think that was causing the spark to not actually ignite the fuel. After removing the spark plug, thoroughly cleaning it and fixing the spark plug boots and wire, the engine seems to be firing correctly now. Would that make sense or did I just get lucky?
Click to expand...
Makes sense, but what exactly did you do to 'fix' the plug cap and wire? If the cap is leaking spark through the body of it to the engine (ground), then they typically need to be replaced. Did you trim the end of the plug wire about 1/4" before screwing the cap back on the wire?
 
HI all,

It's been a while but I've had the bike stored for the winter. Right before I put it away, I was having some issues with the battery which I chalked up to a bad battery. I've been using a lead acid battery that requires constant recharging. I now have a awg battery with good charge but have one issue. My headlights, blinkers and break light works but the running taillight which I understand should always be on does not seem to come on. Any ideas what I should check in order to diagnose this issue?
 
carteredward4 said:
Break light does work
Click to expand...
Eric was suggesting that the filament for the tail light may be burnt, which is separate from the filament for the brake light.

It's easy to check. Pull the bulb out and use jumper wires to test each filament by connecting directly to 12V. There are two contact terminals on the base, one for each filament, and ground is the outside metal case. You could probably even use a 9V battery for this test.

It could also mean a bad connection for the power side of the tail light, which is typically carried by a brown wire, as opposed to green/yellow for the brake light. Sometimes the spade connector will work loose on the back of the tail light, so have a look-see there.
 
If the brake light works with the proper brightness, and when you turn the ignition switch to the Park position the taillight comes on, the problem is not the bulb or the ground. The taillight does not come on automatically with the key, it only comes on when the headlight switch is in the On position for low or high beam.
 
Last edited:
ancientdad said:
If the brake light works with the proper brightness, and when you turn the ignition switch to the Park position the taillight comes on, the problem is not the bulb or the ground. The taillight does not come on automatically with the key, it only comes on when the headlight switch is in the On position for low or high beam.
Click to expand...
Thanks all for the insight. I went ahead and got a replacement bulb. I installed the new bulb today but I think I have a bigger issue. Each time I press the break, my fuse blows. Any ideas? I guess there must be a hot wire touching the frame or something but I haven't done anything with the wiring aside from making sure all the connections running to the taillight are connected.
 
Happened to me before. In my case, one of the green/yellow wires was rubbing the frame and the shielding got worn through, leading to a short when the brake was applied.

You'll likely need to go over things very carefully to locate it, starting with all wires that connect to your brake switches.
 
stl360+450 said:
Happened to me before. In my case, one of the green/yellow wires was rubbing the frame and the shielding got worn through, leading to a short when the brake was applied.

You'll likely need to go over things very carefully to locate it, starting with all wires that connect to your brake switches.
Click to expand...
You were correct. It appears that at least the yellow/green and yellow wires that run through the rear fender were broken and likely contacting the fender. Should I splice in new wires or is there another way of fixing these cracks? It appears like the wires themselves are mostly intact.
 
If you just need to reinforce the worn areas, you could put shrink tubing over the compromised section(s), but you'd need to pull the wires and then redirect them through that channel in the fender.

If you prefer to use new wires, you could have a look at Vintage Connections. If I'm not mistaken, there may even be a VHT discount code. You'd probably have to buy the wire and any bullet or spade connectors needed to reproduce the damaged wires.
 
stl360+450 said:
If you just need to reinforce the worn areas, you could put shrink tubing over the compromised section(s), but you'd need to pull the wires and then redirect them through that channel in the fender.

If you prefer to use new wires, you could have a look at Vintage Connections. If I'm not mistaken, there may even be a VHT discount code. You'd probably have to buy the wire and any bullet or spade connectors needed to reproduce the damaged wires.
Click to expand...
I was able to get some shrink wrap on them and they now do not blow my fuse! Thank you for the suggestion. My speedometer does not seem to be working. The wire running from the speedometer seems to twist freely, and I can see the spindle twisting when the front wheel turns. When I link them up, and tighten the little set screw I do not see the top of the speedometer wire turning. Any ideas?
 
carteredward4 said:
I was able to get some shrink wrap on them and they now do not blow my fuse! Thank you for the suggestion. My speedometer does not seem to be working. The wire running from the speedometer seems to twist freely, and I can see the spindle twisting when the front wheel turns. When I link them up, and tighten the little set screw I do not see the top of the speedometer wire turning. Any ideas?
Click to expand...
It's possible the tangs on the ring gear in the speedo drive inside the front hub aren't correctly engaged, it's an easy mistake to make when reassembling the front wheel after a tire or brake change. Did you check that the inner cable isn't broken and turns the same at both ends?

speedo drive notches.png
 
Thank you for the swift reply! I took off the front wheel and inspected the speedo drive. The part attached to the wheel seems to be worn. Do you think it still has enough of an indentation for the splines on the hub piece to spin when the wheel is in motion. This is my first time taking off the front wheel on this bike, so the previous owner may have installed it incorrectly. When I spin the part attached to the hub, the end of the speedo cable twists like it should, so I believe the cable itself is fine. I'm guessing either the part was not set in the indents, or the part on the wheel is too worn to spin the piece attached to the hub.
PXL_20260312_032629337.jpg
Part attached to hub. Needs a good cleaning for sure.
PXL_20260312_032600284.jpg
Part within the wheel
PXL_20260312_032604734.MP.jpg

Does this look worn, are is this the correct depth?
 
Last edited by a moderator:
Thanks Richard. Does the rubber gasket need to come out in order to remove the speedo drive? If so, is there a good way of doing that which reduces the chances of tearing it?
 
On futher inspection, I was able to remove the speedo drive without removing the black rubber gasket from inside the hub. Attached are photos of the speed drive. It looks like they should be bent upwards from the photo you provided. About how many mm are they bent? Attached are photos for reference. 431.jpg430.jpgPXL_20260312_123734146.jpg
 
This is what it should look like. The tabs on yours are bent because previous re-installations of the front wheel have been done without paying attention to the positioning of the tabs in the notches in the hub, so they landed on the high spots of the hub and were bent inward. They should be flat, not bent down, and should be 90° to the gear. I couldn't find a true side shot of one, this is the best angle I could get.

1773320782981.png
 
Thank you! I was able to bend mine back. Photo attached. Going to try and reattach the wheel with the correct alignment tonight. Is there a good diagram to look at that shows the correct sequence of washers, bearings and nuts for the front wheel? I try and take things apart in a sequence with photos but some washers dropped out as I dislodged the wheel. Also, what grease is recommended for application to these parts?
PXL_20260312_153142652 (1).jpg
 
carteredward4 said:
Thank you! I was able to bend mine back. Photo attached. Going to try and reattach the wheel with the correct alignment tonight. Is there a good diagram to look at that shows the correct sequence of washers, bearings and nuts for the front wheel? I try and take things apart in a sequence with photos but some washers dropped out as I dislodged the wheel. Also, what grease is recommended for application to these parts?
Click to expand...
Have you used any of the resources in the Welcome Package of helpful links I posted in my reply to your introduction? Online parts fiches are very helpful for this kind of thing. First, this link to read:

Tips for identifying and locating parts

Lots of people new to the vintage Honda motorcycle world are unfamiliar with how to identify the parts they need and where to look for them. The question is often asked: "Where can I find a (part name)?" The first step to finding any part for any of our favorite Hondas is to properly identify...
www.vintagehondatwins.com www.vintagehondatwins.com

Then a quick trip to CMSNL, Partzilla or NOS Parts Now for these:

honda-cb175k6-super-sport-1972-usa-front-brake-panel_bigma000159f06_7da2.gif


honda-cb175k6-super-sport-1972-usa-front-wheel_bigma000159f07_bebd.gif
 
I appreciate you reminding me of those links. The parts fiche is very helpful. I guess whoever installed the the front axel was not going by the diagram, because it was backwards. The castle nut was on the side with the brake drum.
 
carteredward4 said:
I appreciate you reminding me of those links. The parts fiche is very helpful. I guess whoever installed the the front axel was not going by the diagram, because it was backwards. The castle nut was on the side with the brake drum.
Click to expand...
This, along with the past hands-on experience many of us have here, is how you sort out things that aren't covered by the FSM. And with the way "help" videos online are today, you can't trust them either because many if not most of the videos are being done by people who weren't even born when these bikes were new and current models. So if it was wrong when they got their hands on it, they would likely think it was correctly assembled.
 
I've got everything mostly together for the front wheel. The speedometer seems to work now! Thank you all. One question I still have is how to parts 13, 17 and 21 go together with the fender and left front fork? Does it go left front fork, part 13, 12, 17, fender and then part 21?
1773423360530.gif
 
My neutral light doesn't stay on which seems to keep the bike from starting. I've noticed that if I fiddle with the spark plug connector that the switch will come back on but then it goes off once I attempt to start the bike. Any ideas?
 
carteredward4 said:
My neutral light doesn't stay on which seems to keep the bike from starting. I've noticed that if I fiddle with the spark plug connector that the switch will come back on but then it goes off once I attempt to start the bike. Any ideas?
Click to expand...
Another odd thing about this is that it seems to work intermittently. I started it up no problem last night but today it is not functioning
 
There is no direct correlation between the spark plug lead and the neutral switch, think that must just be a coincidence.

The neutral light in the speedo head is connected to a live feed when the ignition is switched on. The other side of the light is connected to a wire which is grounded (connected to frame earth ) when neutral is selected in the gearbox. In my photo below you can see the neutral switch, a flimsy brass spring arrangement. The ground wire from the neutral light connects to this via a bullet connector plugged into the brass switch. The circuit is completed ( light comes on) when the gear selector drum is rotated to the neutral position, as in the photo. It's the piece of metal under the cross head screw, connects to the switch and thence to ground.

So, an intermittent light can be due to a poor connection at the bullet connector, or simply that the brass spring arrangement is bent or covered in chain lube.

1777187213896.png
 
Richard Pitman said:
There is no direct correlation between the spark plug lead and the neutral switch, think that must just be a coincidence.

The neutral light in the speedo head is connected to a live feed when the ignition is switched on. The other side of the light is connected to a wire which is grounded (connected to frame earth ) when neutral is selected in the gearbox. In my photo below you can see the neutral switch, a flimsy brass spring arrangement. The ground wire from the neutral light connects to this via a bullet connector plugged into the brass switch. The circuit is completed ( light comes on) when the gear selector drum is rotated to the neutral position, as in the photo. It's the piece of metal under the cross head screw, connects to the switch and thence to ground.

So, an intermittent light can be due to a poor connection at the bullet connector, or simply that the brass spring arrangement is bent or covered in chain lube.

View attachment 57186
Click to expand...
Thanks so much for this helpful information. I plan on digging in to the repair later today. I did make an error in my previous post though. I accidentally said spark plug connector instead of fuse connector. Would a bad fuse connector cause this issue and is there some way of testing if it's bad?
 
carteredward4 said:
Thanks so much for this helpful information. I plan on digging in to the repair later today. I did make an error in my previous post though. I accidentally said spark plug connector instead of fuse connector. Would a bad fuse connector cause this issue and is there some way of testing if it's bad?
Click to expand...
Your description above seems to indicate loss of power (not just the neutral light) so yes, a poor connection at the main fuse (the only fuse in the wiring harness) could be a factor.
 
Looks like it was some sort of connection issue. I will likely swap out that fuse withe the blade fuse as suggested by Richard. Bike is now cranking and neutral light stays on but I'm still not getting it to start. I've checked that gas is getting to the carbs by loosening the carb drain screws. My spark plugs are firing and I get a pop every once in a while.
 
A number of things can cause a no start - first thing I'd check if it won't start but pops every now and then is that you have the timing right.

Next up is test compression right after a failed start. check the plugs as you pull them to see if they have fuel on them.
 
carteredward4 said:
https://photos.app.goo.gl/jg9fbb8a4NTBJQqv7
Click to expand...
I hope you all can see this video. The bike ran for a while today which I think was dumb luck. It seems like the fuse connection is bad and so if it is wiggled just a bit the bike shuts off. Im not sure if that explains the fuses getting blown, but I might have discovered that issue as well. It appears like my light blinker was sparkling off the starter solenoid. What style blade fuse box should I purchase? 32v 15 amp? How does it connect to the bullet connector attached to the wire running to one side of the fuse? Should I get another bullet connection or purchase something else? Thanks as always for your help!
 
carteredward4 said:
I hope you all can see this video. The bike ran for a while today which I think was dumb luck. It seems like the fuse connection is bad and so if it is wiggled just a bit the bike shuts off. Im not sure if that explains the fuses getting blown, but I might have discovered that issue as well. It appears like my light blinker was sparkling off the starter solenoid. What style blade fuse box should I purchase? 32v 15 amp? How does it connect to the bullet connector attached to the wire running to one side of the fuse? Should I get another bullet connection or purchase something else? Thanks as always for your help!
Click to expand...
I've been trying to watch it since the first minute it was posted, still haven't seen it yet. Sits there saying it's getting it ready.
 
All of the power for the bike runs through that fused link. If it's not 100% rock solid, troubleshooting anything else before fixing that is an exercise in futility. You may be able to just open up the fused holder, clean the contacts and check that the spring is still springing.
 
EzPete said:
All of the power for the bike runs through that fused link. If it's not 100% rock solid, troubleshooting anything else before fixing that is an exercise in futility. You may be able to just open up the fused holder, clean the contacts and check that the spring is still springing.
Click to expand...
Well that might be part of the problem. The spring is not springing.
 
You must log in or register to reply here.
Back
Top Bottom