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Discussion Starter · #1 ·
Hey guys recently I picked up two cb400t, the one I’m working on is a hawk 1 and I wanted to update the headlight and speedometer. Now the issue I’m having is that I must have broken the circuit somewhere because the entire bike doesn’t have any power. I check the battery it’s brand new and fine so I’m assuming it’s a ground issue. Do these bikes need to have every ground connected working? (I disconnected the taillights aswell) I’m handy and have worked with electrical issues before and I have the original fsm with the diagram but I’m stumped please help
 

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I recently replaced a cracked headlight bucket on my '79 CM400 and had the same issue.

First, yeas all grounds need to be connected to be grounded. In my headlight there was a connector that connected each turn signal and the headlight ground to a fourth wire that I assume went to the frame. One plug was a little loose. Fixed that and it worked. For a day.

So I looked at and cleaned every connector and put it back together and it worked. For one day, lol. So I checked every ground and all were good. All fuses were good.

I then found that the hot wire soldered to the ignition switch had broken off (the solder ball was gone) and was apparently making intermittent contact. Probably from manipulating all those wires and plugs in the headlight bucket.

I had never soldered anything electrical before in my life but it wasn't hard. There was a little extra wire length, so I was able to cut it back about 1/4" to clean up the end. Just be sure use rosin core solder (and a soldering iron, not a torch, lol).
 

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Discussion Starter · #3 ·
I recently replaced a cracked headlight bucket on my '79 CM400 and had the same issue.

First, yeas all grounds need to be connected to be grounded. In my headlight there was a connector that connected each turn signal and the headlight ground to a fourth wire that I assume went to the frame. One plug was a little loose. Fixed that and it worked. For a day.

So I looked at and cleaned every connector and put it back together and it worked. For one day, lol. So I checked every ground and all were good. All fuses were good.

I then found that the hot wire soldered to the ignition switch had broken off (the solder ball was gone) and was apparently making intermittent contact. Probably from manipulating all those wires and plugs in the headlight bucket.

I had never soldered anything electrical before in my life but it wasn't hard. There was a little extra wire length, so I was able to cut it back about 1/4" to clean up the end. Just be sure use rosin core solder (and a soldering iron, not a torch, lol).
Thank you for replying! When you say all the grounds does that mean the ones on the back of the bike aswell? Because they are not connected and since my new headlight is one of those universal types would the grounding location for the blinkers matter?
 

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That is exactly what happened to my CM400T!
(Bad solder joint on the ignition switch)
I recently replaced a cracked headlight bucket on my '79 CM400 and had the same issue.

First, yeas all grounds need to be connected to be grounded. In my headlight there was a connector that connected each turn signal and the headlight ground to a fourth wire that I assume went to the frame. One plug was a little loose. Fixed that and it worked. For a day.

So I looked at and cleaned every connector and put it back together and it worked. For one day, lol. So I checked every ground and all were good. All fuses were good.

I then found that the hot wire soldered to the ignition switch had broken off (the solder ball was gone) and was apparently making intermittent contact. Probably from manipulating all those wires and plugs in the headlight bucket.

I had never soldered anything electrical before in my life but it wasn't hard. There was a little extra wire length, so I was able to cut it back about 1/4" to clean up the end. Just be sure use rosin core solder (and a soldering iron, not a torch, lol).
 
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