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Question: Bike starts, idles will not run
Ignitor box - 0 (0%)
Plugs, wires - 0 (0%)
Valve Adjustment - 0 (0%)
Carbs - 4 (100%)
You tell me - 0 (0%)
Total Voters: 4

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Author Topic: CB650 Running Issues  (Read 301 times)
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dirthawk Topic starter
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Bike: 1983 nighthawk 650
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Join Date: Aug, 2011




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« on: August 11, 2011, 08:08:32 AM »

Hey I just bought a 1983 Nighthawk 650.  I'm technically inclined and have built motors in a couple cars but not in awhile, now I mostly work on dirt bikes.  This is my first road bike and I don't feel like trouble shooting the issue, so maybe someone can help me.

The bike will start and idle just fine (with the choke on) after it warms up it can idle with the choke off, but will usually die with the twist of the throttle.  With choke on, I can twist the throttle semi-slowly and the bike will stutterly raise in RPM until about 5500 and doesnt really go past that.  If after I have the RPM's up I WOT it will stay at a consistent bog, burrrrrrrrrrrrrrrap. POS, so it seems like it could be the carbs but I took them off (pain in the ass) and cleaned them and no luck.  Might have to get them tuned? Or maybe its electrical?

PS I checked the plugs, they are ok, however one of the wires has some damage-a no no I know.  Can one cylinder misfiring cause this much grief? The bike will NOT drive under load, its dies everytime I try to ride it (except the first time where it left me stranded at the bottom of the hill.)  Any help is appreciated thanks!
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« Reply #1 on: August 11, 2011, 08:17:44 AM »

I would look at the carbs and fuel system. Check this link on cleaning your carbs as one bank with Pine-Sol:
http://nighthawk-forums.com/index.php/topic,4472.0.html

How does the tank look? Rusty?
I'd pull the petcock and clean it out.

Does it have a new air filter? Has the airbox or exhaust been modified in anyway?
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Technical answers based on experience
dirthawk Topic starter
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Bike: 1983 nighthawk 650
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« Reply #2 on: August 11, 2011, 08:36:30 AM »

Good call on the petcock totally forgot about that...Also missed the NOT A NIGHTHAWK sticky on the top of the thread  drooler knary yes gas tank is rusty...Pine-sol huh...ok
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