New '82 Nighthawk 650 owner, having a few problems.

If it's broken or just needs tweaked

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e_filippo
Posts: 4
Joined: Tue Jul 17, 2018 6:06 pm

New '82 Nighthawk 650 owner, having a few problems.

Postby e_filippo » Wed Jul 25, 2018 10:56 am

Hey guys, I've had my nighthawk for a few months and I'm finally getting around to trying to fix some if it's issues. However, I need some help from the experts. I'll tell you what it's doing and see if you can come up with any more ideas, as I'm pretty much out. Here we go:

1) I can't rev past 5k unless I'm at like 1/8 throttle. It'll get up there and sound like it hits a rev limiter. The more throttle I give it, the lower that "rev limiter" gets. I typically have to ride around at about 1/4 throttle to be able to ride it normally. I'd like to be able to give it a little more throttle, especially on the highway. I can't really get over 65 due to this issue.

2) After a bit of riding, maybe 30 miles or so, the bike will start to rev itself slowly when I stop at a light or something. Before that point, it idles fine, if not a little high, but if you let it go, it'll rev itself into a low Earth orbit. I usually use the clutch and bring the revs back down, but I can't say I'm the biggest fan of having to do that. Sometimes, I'll just shut it off when I'm sitting in traffic to keep it cool.

3) The revs will increase when I pull the clutch in to shift gears. It'll go up to about 4-5k if I let it, but will hold it there for a second if I don't shift and let out.

4) The throttle surges after giving it more than 1/2 or so and letting off.

These are the biggest issues I'm having with it, but I'm not sure where to go from here. My carb boots were pretty cracked when I got the bike, so I replaced them with new ones and it got a little better (idling and starting), but I'm not sure what else to look at. Vacuum leak? Is it running too lean? I have no idea!

Let me know what you guys think, I appreciate any help you can give me!

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Folsoml
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Location: North Florida

Re: New '82 Nighthawk 650 owner, having a few problems.

Postby Folsoml » Wed Jul 25, 2018 12:05 pm

I'd wager you have an air leak. Let the bike idle, and spray some brake cleaner (not carb cleaner) on each of the carb insulators. Any change in idle is an indication of a leak.

Good luck!
Have a problem with your CB650? Have a technical question? Click here!


My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

e_filippo
Posts: 4
Joined: Tue Jul 17, 2018 6:06 pm

Re: New '82 Nighthawk 650 owner, having a few problems.

Postby e_filippo » Wed Jul 25, 2018 12:11 pm

Folsoml wrote:I'd wager you have an air leak. Let the bike idle, and spray some brake cleaner (not carb cleaner) on each of the carb insulators. Any change in idle is an indication of a leak.

Good luck!


To be clear, do you mean the carb boots? I tried that after I installed them just to make sure everything was sealed correctly, and there was no change in RPMs while spraying each one.

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Folsoml
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Joined: Sat Apr 07, 2012 9:02 pm
Location: North Florida

Re: New '82 Nighthawk 650 owner, having a few problems.

Postby Folsoml » Wed Jul 25, 2018 5:07 pm

Has it been doing this all along, or is it a new development? It may be worth checking again.
Have a problem with your CB650? Have a technical question? Click here!


My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

e_filippo
Posts: 4
Joined: Tue Jul 17, 2018 6:06 pm

Re: New '82 Nighthawk 650 owner, having a few problems.

Postby e_filippo » Sat Jul 28, 2018 12:38 pm

Folsoml wrote:Has it been doing this all along, or is it a new development? It may be worth checking again.


It's been doing this all along, at least as long as I've had it.

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Volker_P
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Location: southern Germany

Re: New '82 Nighthawk 650 owner, having a few problems.

Postby Volker_P » Tue Jul 31, 2018 3:19 am

Welcome here! :D

How do your plugs look like? All four equal? Still the plugs you got with the bike?
When you replaced the old carb boots, did you also have a look inside the carbs?

First thing for me to try for now would if throttle response gets better when the choke is pulled a bit.

I would not to be too optimistic to get a bike of unknown history and doing these things back to running reasonably without going into the carbs. :wink:
Cosky's great (free) online manual: http://cosky0.tripod.com

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