93 Nighthawk 750 cuts off intermittently

R8venK1ng

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My 93 CB750 cuts off intermittently. What I mean is I will turn the key to the ON position, and the lights will come on, then a few seconds later, they cut off. I can literally start the bike, and seconds later the bike will cut off, no lights, no power. It does this intermittently. The fuses in the fuse box are not burned out, I haven't checked the fuse in the headlight yet. I have checked the starter solenoid, and the connections are clean, so are the connections on the battery terminal. I took the battery to be tested, and the Advanced Auto confirmed the battery was good. I haven't checked the connections on the ignition switch yet either. I'm thinking it's the ignition switch connection
 
I ran into similar symptoms a couple weeks ago.
I warmed up the bike. Took it for a spin. Parked it for a minute to grab my stuff, turned the key again, no power.

## Symptoms

Suddenly absolutely zero power to anything, not to headlight, to gauge cluster, nothing. Not a sign of a weak battery.

## Troubleshooting

The ignition circuit. Checked fusebox and fuses, all good. Opened the front headlight housing. Inside it I found the connector leading to the ignition switch (2-wire red and red&whitestripe). Noticed some melted features on the sides of the white connector. With the ignition switch key switched to on, jiggled wires and connectors. Power would intermittently come on.

## Cause

Heat build-up from loose wire connection at the terminals of the connectors, loose connection increases electrical resistance, i.e. heat, melted enough plastic to loosen the contacts more, vicious circle. That also explains why it could happen while riding, as the wires take a bit of time to heat up.

## Solution

Honda changed out the part number for the ignition switch, and the wire harness. So, if I get a new ignition switch, I might need a new wiring harness, too. I actually did search for Honda's connector specifications, but those individual pieces are too hard to find where I'm from. I'm afraid of having to rewire an entire bike, so I'll I might splice/solder some wiring ends as suggested also in
https://www.cb750.com/threads/replacement-connector-plugs-92-cb750-nighthawk.9382/,
or just bite the bullet and get a new ignition switch.
 
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I opened the headlight housing and found the connector for the ignition was hot. The metal arms holding the wires was making contact with the connector, and heating it up. I moved it, and no more shut off. Thanks for the assistance
 
Good to hear.

Just a warning, theoretically those metal arms shouldn't have any influence on the connector, if it's just rubberized metal arms touching the plastic of the connector, or the plastic insulating sheathe of the wire. So I have a feeling your issue is like what I and others have experienced with this bike (see previous message's link to other post).

If you notice it's still heating up, that's going to be a problem that'll bite you later on. That heat buildup will mess with the connector more and more. I say this because I also tried the quick fix of taking some pliers and just lightly twisting a tiny bit the connector terminal's tangs so that they'd have a stronger contact with the female ends. It was rock solid, and jiggling the connector no longer flickered the power... but it still got hot. Hell, leave it on long enough, the rest of the wire would get hot, travelling up towards the switch itself.

Turns out the real source of the problem was that the wire no longer had a good hold of the terminal at the crimp. Yesterday I (fortunately) got back to my driveway from my 15-minute test ride, and that was enough time to warp the connector from the heat such that tapping the thing would make the bike's power flicker on and off.

I decided to do a butt splice repair instead of plunking down 100+ Canadian moneys for a new ignition switch only for its fresh connector. My logic is that I don't foresee having to disconnect this ignition switch anytime soon (it's the connector's fault that all this crap happened anyway), and the tools and supplies I buy can also fix the busted speaker connection in my car. Two birds: Learning to fix stuff, and cheaping out in the process.

Just a note: my harness end for the ignition circuit is 14 AWG wire. Then I find out only after stripping for fresh wire at the ignition switch's end that it's 16(, or maybe 18?) AWG. This didn't work out with a symmetrical butt splice connector, because the ignition wire end would just slip out of the crimp. So I had to buy some step-down connectors. Tested by leaving the bike on with a charged battery for 10 minutes. Zero heat at the splice, or the wires.

Sorry to hijack your post with my experience, just felt it worth posting, for whoever else is afflicted.
 
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