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Old 04-09-2008, 10:15 PM   #1
Saki
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Question Help me help my friend with his 4-carb bike

So my friend went out and bought a 1983 Honda Nighthawk, cb650. It ran well enough, but he thought it was misfiring so he decided to change the plugs. He put in new plugs, and of course, now the bike won't run - it seems to be running waaay rich and the plugs are getting drenched. With starter fluid, the bike will idle until the fluid is consumed, then die.

He told me he's tried leaning the carbs, but isn't having any luck, and I think his carbs are way out of whack now. By the way, this bike has FOUR carbs... one for each cylinder.

I told him I'd comeover to look at it, but I have no idea how to get four carbs close to tuned to even get the bike running rough. Does anyone here have any advice or links to working on this old bike?

Tia,
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Old 04-10-2008, 04:46 AM   #2
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1. Get a service manual.
2. Take the carbs off and get them CLEAN!
3. Get all settings back to factory spec.
4. Put them back on and synchronize.
5. If all that fails, sell it to the next guy and get something that runs right.
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Old 04-10-2008, 04:59 AM   #3
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You can't 'lean' those carbs without taking them apart. The adjustment screws only affect idle mixture. They should be turned carefully all the way in until they just kiss the seat. Then turn them out 1 1/2 turns. That should be the initial setting. He'll need a manual to do the full adjustment procedure.

But really, longride is right. The carbs should be pulled and cleaned and set to factory spec. A float or two are likely stuck open and flooding the engine.
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Old 04-10-2008, 07:19 AM   #4
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Not to be rude here but niether you nor your friend seem to know what you're looking at. The best thing you can do at this point is take it to a Honda or independent mechanic and have them put it right for you.
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Old 04-10-2008, 07:52 AM   #5
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"Not to be rude here..."

You can stop right there!
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Old 04-10-2008, 08:07 AM   #6
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Originally Posted by sarnali2 View Post
Not to be rude here but niether you nor your friend seem to know what you're looking at. The best thing you can do at this point is take it to a Honda or independent mechanic and have them put it right for you.
But it's more fun to encourage them to dig into it. Maybe they'll learn something. Maybe they'll end up with a reassembled bike with a handful of little bits left over. Maybe they'll just torch it.
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Old 04-10-2008, 08:11 AM   #7
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Gotta start somewhere, right?
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Old 04-10-2008, 08:35 AM   #8
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Make sure you put gasoline in it, and not diesel. Also, having worked on CB650's, you might want to put your hands in a shrinking machine, so they're about the size of the hands on a spider monkey. Also, when putting the carb rack back on the manifold, boil the rubber manifolds in hot water for a few minutes, so you'll be abble to slide the rack back on without ripping one, or buggering them up. The 550/650 is put together real tight, with little room to work with. Good luck.
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Old 04-10-2008, 08:46 AM   #9
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If the bike was running well enough on the old plugs, I'd try a couple of things. The first is obvious, and that's to throw the old plugs back in, that really shouldn't make any difference at all, but I'm curious. My next thought is that something got "adjusted" in pulling the plugs out. Any chance he accidently got the idle screw adjustment cranked way the heck up by accident, or maybe the choke lever? Don't know why, but something else had to change. I'd take a flash light and take a close look at what they might have changed in getting at the plugs? I recall having a similar problem on an inline 4years ago and finding that somehow I'd created a leak between the carbs and the airbox (obviously it was lean not rich) at the boots when pulling the tank off.
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Old 04-10-2008, 11:14 AM   #10
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Quote:
Originally Posted by mscuddy View Post
boil the rubber manifolds in hot water for a few minutes,
Decant the gravy after boiling and retain for basting the carbs later.
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