1972 CB175: rebuild then restore

[carteredward4]

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.

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?

 

[ancientdad]

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?

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.

 

[carteredward4]

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.

Thanks for the help! I'll inspect it a bit more tomorrow

 

[carteredward4]

Thanks for the help! I'll inspect it a bit more tomorrow

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?

 

[ancientdad]

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.

 

[carteredward4]

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 Common motor for a reasonable price. Is that the best source or is there a better one?

 

[ancientdad]

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 Common motor for a reasonable price. Is that the best source or is there a better one?

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 CMC. 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.

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

Here's a seal set for barely over half the price of CMC

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

 

[carteredward4]

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.

 

[ancientdad]

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.

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.

 

[carteredward4]

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.

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?

 

[ancientdad]

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?

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?