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I just came across this forum today and after a few reads discovered there is a wealth of knowledge here. With that said I recently have come into a problem that is making my head spin. I have a 1983 Honda CB550SC (Nighthawk) that is starting to act up. I am thinking it is a broken wire, but am wondering if anyone else has had this problem. It seems that when I turn the bike to the stops to the left I cannot start the bike after this. It turns over strong, but a spark check reveals a weak spark on all cylinders. I play with the wiring behind the fuse box and sometimes it works and fires right back up. Now last night I tore into this problem some. I took apart the front assembly to get at the wiring, removed all the tape, removed the fuse box, unplugged all the connectors and checked every wire. I could not find a break or damaged wire anywhere. What I did find was some corrosion in the wires coming from the right handlebar, but this was on the outside of the wire and no visible breaks in the sheath. So I cleaned all the connectors and put it all back together. Upon doing that I noticed 1. My signal lights were on all the time like driving lights with the headlight now and 2. If I wiggled the wiring harness my headlight would go out. This is still making me think of a broken wire, but I never did check to see if the headlight was out when the bike would not start. Now can anyone think of where to start looking foe tuis gremlin in the wiring? I plan on tearing into it again and have a wiring diagram, but not one that shows when and what lines are hot. Any suggestions are welcome. Thanks.
 

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1. My signal lights were on all the time like driving lights with the headlight now and
2. If I wiggled the wiring harness my headlight would go out.
1) That is the way those lights are supposed to work, so you are making some progress.

2) Maybe you have two problems here. IIRC, on that model the headlight was NOT switched off when starting, so maybe your battery is getting weak and starting fails when the headlight is ON like it should be.

Some Hondas much older than that one had problems with the grounds for the front lights. Check to see where the ground wires go before tearing the harness apart again. Likely the problem is in a connector or loose frame ground.
 

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Yup, I agree: probably a bad ground, most likely where the harness goes right at the steering head, which is why problems pop up when you turn the bars all the way to the right.
 

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Little bit of an update. I am glad to hear that the front signal lights are supposed to be on, I was going to leave them wired like that even if they were not supposed to be. The ground idea seems to be spot on, but it is actually at the fuse box. I realized after it was all back together that the bike started better than it ever has. There is great spark now. My wife went out for a ride and came back saying it rides perfect, but no neutral light/tach/oil light working. So back behind the headlight I went. Checking voltage on the wires showed good voltage to the cluster so I started chasing the ground, which was giving me some odd voltage readings. I followed it to the connector on the back of the fuse box. Pressed on the wire at the connector and lo and behold, the aforementioned lights came on. Did the same for the headlight connector on the fuse box and it too simulated the wiring gremlin. Seems that there is some bad connection/bad wires at the connectors. So for now, I think I am going to ride since this is the first nice weather we are getting. Just not go too far from home! Come the cold weather, time to tear in and refit the connectors and fuse box. Thanks for your help!
 

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Seems that there is some bad connection/bad wires at the connectors.
The problem likely is in the connector pins themselves and unplugging and re-plugging will often effect a temporary cure.
If you spray them with contact cleaner while apart, that is often all you need for a long term cure.
 
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