Honda Twins banner

No Power 1982 CM250 C

7K views 23 replies 4 participants last post by  66Sprint 
#1 ·
Hi Everyone,

Hopefully this is a simple fix or someone can point me in the direction of a sticky that addresses this. Any and all help greatly appreciated!

Here are the symptoms:
No power to lights, starter, horn etc.
Previously, all electrical was in good working order. Nothing electrical was replaced on the bike recently.
Battery showed some signs of sulfating so I replaced it.

Current Battery Reading: 12.8V
Solenoid: 12.8V
Ignition Switch: 12.8V
15A Main Fuse: 12.8V
7A Fuse Tail Light: 0.0V
7A Fuse Headlight: 0.0V

I tried to test the Ignition/Kill Switch continuity by using the B/W wire at the CDI box and the BATT- terminal and got this:

Ignition Off/Run Off = 0.00
Ignition On/Run Off = 0.00
Ignition On/Run On = L
Ignition Off/Run On= L

Fuses all Read: 0.00

So my question is are the 7A fuses supposed to receive power before the bike is on? If so, do I need to replace the fuse holder since the fuses are all good?
I have the FSM but it doesn't really address the fuses other than to say " If there's no power, a faulty fuse should be suspected." I have the wiring diagram as well, maybe someone here can help me translate it?

Thanks everyone!

Jess
Technical drawing Plan Drawing Diagram Engineering
 
See less See more
1
#2 ·
The ignition is separate from the chassis electrical system, it is not connected to the battery. When the kill switch is in the off position or the ignition switch is in the off position either provides a connection from the CDI black/white wire to ground.

Are you checking voltages to the battery negative post or to the frame?
 
#3 ·
I was checking the voltages to the battery negative terminal which at the time was hooked up to the ground wire. What do you think the next trouble shooting steps should be? I’m having a hard time determining what would cause the 7A fuses to show no voltage.


Sent from my iPhone using Tapatalk
 
#4 ·
Power runs from the battery to the solenoid to the 15A fuse to the ignition switch. The ignition switch routes power to other circuits with the key turned to On or Park. The 7A fuses won't have any power supplied to them with the key Off.
I would go to the ignition switch connector and back probe the connection for
Key OFF = power on the Red wire only
Key ON = power on the Black, Brown and Brown w/White
Key P or Park = power on the Brown wire only
Key OFF there will be continuity between the Green and Black w/White which is the grounding circuit turning the CDI off.
 
#6 ·
Okay I’ll do that today. A bad ground was one of the first things I suspected so I’ve already swapped the ground cable and connectors and cleaned up all connections with a wire brush but no dice. I’ll report back with my findings on the ignition switch this afternoon!


Sent from my iPhone using Tapatalk
 
#7 ·
Okay, so as you expected, JT, no voltage when testing those points to the frame. No voltage from any of the fuses to the frame either. So this leads me back to the battery. Since there is no voltage to the solenoid when testing to the frame, that means it must be the battery ground, correct? I can recheck those connections I re-did yesterday unless the ground at the solenoid is what's causing the issue.
 
#9 ·
Yes, the frame is powder coated but I made sure to attach the test ground connection to a bare spot underneath where the original ground cable was attached. I'm getting nothing which now leads me to believe I don't now how to use a multimeter... :LOL:
 
#10 ·
Okay, so I'm back to thinking its the ignition now. Tested everything with a new ground cable on the battery at the original ground point and used the starter motor as my second test ground point.

Batt+ to Frame= 12.8V
Main Fuse to Frame= 12.8V
Solenoid to Frame= 12.8V
7A Fuses to frame with Ignition ON= 0.0V

I should be seeing voltage on those fuses with the Key ON if the ignition switch was working properly right? The ignition has always been a little wonky since I got it anyway because the previous owner lost the keys and had new keys made for it.
 
#11 ·
Yes, you should see voltage with the key on. Go to the ignition switch connector directly and back probe the harness side of the connection, if no power use the switch side. This will confirm that it's a switch problem, not a bad spade connection.
Back probe means the connector is assembled and you are testing where the wire enter the connector.
 
#14 ·
Your switch is dead. You can take it apart and try cleaning/fixing it are find a new one.
Honda is NLA, CMSNL has one for 60 Euro plus 27.50 shippling, David Silver Spares doesn't have it.
Here's the part number 35100-465-771
 
#15 ·
Well I'm still in disbelief, but I was able to fix it!
Normally, I would have been thrilled that a replacement was only $20 and ordered it and went about my day but since I'm stuck in quarantine with nothing else to do, I actually took it apart and was able to get it working again.

I clipped back the wires connecting to the bottom of the switch, re-soldered them (poorly, but effectively), sprayed it out with lock cleaner and put it back together making sure black/white and green had continuity on OFF and Red and Black had continuity at ON and threw it back on the bike and she came right back to life! The switch actually feels much more stable now than it did when I got it. I think when the previous owner lost his keys he did some damage.

Thanks for the help, guys. I have way more confidence diving in knowing you guys are here!
 

Attachments

#16 ·
Good deal.
That switch looks identical to the CM/CB 400/450 series. The electrical circuitry is identical. Are the key positions Off, Run/On, Park/P? If so then the questions would be wiring arrangement in the connector, spacing of the mounting holes and height from the top of the mount.
 
  • Like
Reactions: jwormy
#18 ·
I seem to be having a new electrical issue that I can’t quite figure out. My tail light doesn’t come on in the “ON” position, but it will in the “PARK” position. Brake light works fine from Switches. I also seem to have lost my speedometer backlight. I’m not as concerned about that but they went at the same time so I was assuming it was related to the same issue. I checked both bulbs and the fuses first and they are all good. Then I went to the ignition switch assuming that was the problem and pulled it and tested continuity against the service manual in all positions and it is good as well. I check the ground cables and those seem fine. What am I missing? I had to install a new headlight bucket recently as my old one was cracked and had to disconnect everything and reconnect to fit everything in the new bucket. I used the wiring diagram and triple checked that I had the cables plugged in to the proper spots. I’m lost! Any ideas? Thanks!
Jess


Sent from my iPhone using Tapatalk
 
#19 ·
Jump Brown/White to Brown (key on) and I'll bet the taillight and meter backlights come on UNLESS those bulbs/filaments are burnt out......
You may still have those contacts bad in the key switch, but a permanent jumper wont have any adverse effect unless the key is in the park position (in which case the dash lights will also be on with the taillight)
 
#21 ·
Ugh no dice on the jumper cable from brown to brown/white. The bulbs are definitely good because I swapped them. Tail light comes on in park so I know it’s not a grounding issue. Is there a certain spot I should put the jumper wire? I was putting it on both sides of the ignition connection and neither side worked.


Sent from my iPhone using Tapatalk
 
#23 ·
So brown/white to black will turn it on-intermittently. It worked and then I put the headlight back in the bucket and it stopped working. so either my jumper wire isn’t making a good connection or there’s a loose connection somewhere else
In the line. Should I just buy a new ignition switch? I was really hoping not to have to get new keys....


Sent from my iPhone using Tapatalk
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top