Author Topic: Nighthawk 550 electrical problem  (Read 1303 times)

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Offline Laminar

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Nighthawk 550 electrical problem
« on: March 05, 2009, 05:12:28 PM »
I'm running into a problem with the Nighthawk that I just bought. I was told it just needed a starter, so I picked up a good one and installed it. If I apply +12V directly to the starter, it turns the engine over just fine. Unfortunately, the bike has some other electrical issues. With the battery installed, no matter the key position (on/off/completely out), whenever I press the starter button, the lights come on. The starter doesn't try to crank at all. I also found that if I connect the two wires that are supposed to go to the clutch switch, the fuse at the starter solenoid blows.

I got a tested functional wiring harness and installed it, only to continue to have the exact same issue. I have a new starter solenoid on the way. Any ideas as to what would cause this? All of the handlebar control switches tested functionally correct, so I'm not sure where else to look.

Suggestions?

Offline sangyo soichiro

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Re: Nighthawk 550 electrical problem
« Reply #1 on: March 05, 2009, 05:22:25 PM »
I'm not sure about anything, but this seems awful fishy. 

With the battery installed, no matter the key position (on/off/completely out), whenever I press the starter button, the lights come on. The starter doesn't try to crank at all.

Could it be the ignition switch?  The cheapest way to test this, I think, would be to hotwire the bike.
1974 CB 750
1972 CB 750 http://forums.sohc4.net/index.php/topic,57974.0.html
1971 CL 350 Scrambler
1966 Black Bomber
Too many others to name…
My cross country trip: http://forums.sohc4.net/index.php/topic,138625.0.html

Offline Laminar

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Re: Nighthawk 550 electrical problem
« Reply #2 on: March 05, 2009, 05:32:15 PM »
I tested the ignition switch and it functions correctly - there's continuity across the red and black lines only when the key is in and turned. This is why I'm thinking the starter solenoid might have a short in it that's energizing the bike even without the key turned. Unless there's another component that has power available without the key on that could be shorted - I'm not sure about that though.

Offline sangyo soichiro

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Re: Nighthawk 550 electrical problem
« Reply #3 on: March 05, 2009, 05:47:34 PM »
Yeah... it doesn't sound like the switch.  I'm out of ideas.   ???
1974 CB 750
1972 CB 750 http://forums.sohc4.net/index.php/topic,57974.0.html
1971 CL 350 Scrambler
1966 Black Bomber
Too many others to name…
My cross country trip: http://forums.sohc4.net/index.php/topic,138625.0.html

Offline sangyo soichiro

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Re: Nighthawk 550 electrical problem
« Reply #4 on: March 06, 2009, 09:06:16 AM »
I thought about this a bit more...
I think you may be right about something going haywire in the solenoid.  I guess we'll find out when you get the new part in and try it.

Good luck, and let us know what happens.
1974 CB 750
1972 CB 750 http://forums.sohc4.net/index.php/topic,57974.0.html
1971 CL 350 Scrambler
1966 Black Bomber
Too many others to name…
My cross country trip: http://forums.sohc4.net/index.php/topic,138625.0.html

Offline Laminar

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Re: Nighthawk 550 electrical problem
« Reply #5 on: March 09, 2009, 08:55:35 PM »
GOT IT!

It was the starter solenoid. I got a replacement solenoid and everything started working perfectly. The only problem is that the solenoid is for a slightly different bike, so the fuse isn't actually a fuse, but a strip of metal between two screws. I went ahead and took that out and wired in a fuse holder. Now I just have to get it running correctly!


Offline Laminar

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Re: Nighthawk 550 electrical problem
« Reply #6 on: March 09, 2009, 09:37:05 PM »
Okay, I just want to make sure I have all of the easy stuff done.

I got it to start once - it seemed to idle okay, so I decided to take it to the gas station four blocks away for a full tank of gas. As soon as I rolled in, the bike died. I filled up the tank and added half a can of Seafoam, but then the bike wouldn't start back up. I flooded it trying to start it normally, then finally ended up push starting it, and after a few tries I got it running, but I had to keep it above 3000 RPM or it would die. The ride home was a steady 25mph zone, and the bike was constantly surging - it seemed like one or two cylinders didn't want to fire consistently. After I nursed it home, I changed the oil and filter and ran out and grabbed some new plugs and got those installed, but it seems that the bike flood pretty easily - 5-10 seconds of cranking will leave me with gas dripping out of the overflow tubes.

I discovered that pulling the carbs off of an I-4 bike is a PITA and I'd like to avoid it if at all possible. What's the best way to attempt to start the bike without flooding it? What's the best way to clear a flooded bike? What can I do to help it run better besides an oil change, fresh gas w/ Seafoam, and new plugs?