Topic: My 82 Nighthawk's got problems...new, annoying problems.

[jeepster]

So I went for a ride today for the first time in a week or so of heavy snow. She started right up with no hesitation, but like always, I had to hold open the throttle at 2k to get her to idle reliably. The choke raises revs for a second or two, then they immediately die down and she stalls. After holding the throttle open, she idles nicely. Annoying, but I can live with it. What I can't live with is the sputtering and loss of power when I try to rev past 4k or so in 2nd and third gear...admittedly, I am still, and will most likely remain for the foreseeable future, a noob. I've got around 1k miles under my belt thus far, and have basically been bent over to the tune of about $1k by two different mechanics who claimed to have rebuilt my carbs...twice. So now, the economy, and common sense dictates I have to take matters into my own hands. I've got a Clymer and basic tools. Should get access to garage space this month (I live in Manhattan)

Any ideas as to the cause of the sputtering, lack of power, and crappy idle? I am pretty sure there are timing issue as well, because there is a faint buzzing sound (like a wind up kitchen timer) coming for the left side of the bike. I also noticed that the #1 pipe is a little cooler than the other 3.

[Hush]

Brother I feel your pain,....... as a fellow 650 owner I'm trying to put my finger on your problem.
You have issues if your choke wont operate properly, that's a basic must on these bikes so it shows you have carb issues at least.
Sounds like your slow idle jets are blocked/restricted and that would be why you have to rev till she warms up, you are going past the slow idle jets and using the larger speed (normal riding?) jets to compensate, hey it works but its not right.
I think you said you have a Custom 650, they have some strange attachment to the carbs (only that model) a restricter of some sort, one of the 650 guys on here will put you right on that when America wakes up in about 6 hours.
Most modern mechanics don't understand these dinosaurs (unless they are one themselves and they are getting harder to find) .
As you seem a bit new at wrenching on your bike I wouldn't suggest you rip out the big end any time soon, just fiddle with the bits you can get to know.
Carbs aren't that difficult (I can't believe I just wrote that?) they are a true blue biartch to remove and put back on though.
Probably those overpaid mechanics of yours made some rudimentary blunders as they fought to understand your SOHC bike.
Timing is a thing of ease and beauty with these bikes, you have no points to set or clean and once you figure out how the timing marks align (watch out there are two lots of marks, one for the electrical firing timing and one for the valve timing) you are half way to understanding your bike.
Sometimes we over explain or confuse new members on here, if you get conflicting or hard to understand answers just say so.........we go easy on the newbies here.
So start with plugs, air filter, petrol tap/filter.....all the easy stuff until you run out and then try tackling something a bit more challenging, at some stage you will have a "EUREKA" moment and you'll find the cure......Hush. 

[jeepster]

Thanks. Slow idle jet huh...I'm hoping this is one of those easily accessible bits.  I am running a fuel filter right now as the tank is still a bit of a mess of old kreem...sealing the tank is probably going to be a big first step in keeping my bike healthy.

"I think you said you have a Custom 650, they have some strange attachment to the carbs (only that model) a restricter of some sort, one of the 650 guys on here will put you right on that when America wakes up in about 6 hours."

I do. Its the Nighthawk model. Don't think I like the sound of a "restrictor" on my bike.

I think my order of attack might go something like:

Coat the tank with Por 15
Set timing
pull/inspect/clean carbs
Sync carbs

[Hush]

That sounds like a very sensible aproach Jeepster, try not to bite off more than you can chew initially but as you get more confidence move onto harder things.
Your list would be the same as mine, sort that tank out as bad gas supply is a basic killer for your bike.
Timing (once you read the section of your Clymer) will be quite simple, just remember the two differing timing marks, I have the same Clymer manual and it is not very specific and initially I timed the spark on the valve mark!
I think pulling your carbs is going to be the best thing you ever did for your machine, it aint easy and you will lose skin (and have to frink lots of beer) but once out and on the bench you can clean that sucker and all it's little galleys that block up after time.
I had a Custom 650 up until last week and it was a pig to start until I took the carbs off and cleaned them out, after that she was very well behaved and started and idled as she should.
I'm a bit of a chicken when it comes to synchronising the carbs, I don't have the equipment and don't trust myself to get it right so my old Honda mechanic does that, it's well worth the dollars in my book to get that bit right from the start............best of luck and don't be afraid to ask the dumb questions, if you put "650" in the question line the 650 guys'n gals (eh Kit) will usually come to your aid.......Hush.

[jeepster]

Thanks again. I'm sure I'll have a ton of questions once I get started. If things go well, I will document everything ADV rider style (i.e. a thousand pics) so hopefully my fumbling around with wrenches might theoretically help some future noobs.

[Hush]

That's how I started out and look <-- they call me an expert.....er when did that happen....master!!??

[leekellerking]

I'll be watching, too.

BTW, if you detach the choke cable you have to make sure to readjust it when you reattach it.  Otherwise it blows your power and mileage all to hell.

Don't ask me how I know.   

Oh, and when the previous owner tells you (before he sells you the bike) that his mechanic thinks it needs a rotor in the electrical system, LISTEN to him.  It will save you time and money.
 

Lee
(Whose Nighthawk runs much better today than yesterday)

Thanks again. I'm sure I'll have a ton of questions once I get started. If things go well, I will document everything ADV rider style (i.e. a thousand pics) so hopefully my fumbling around with wrenches might theoretically help some future noobs.

[jkot55]

We have a lot of smaller Nighthawks (250's) where I teach and the problem with them is they are jetted too lean.  Same symptoms that you are having.  We rejet richer and they run a lot better.  Don't know if the 750's have the same problem but might be worth a look.  The mechanics may have rebuilt them to a lean spec and maybe that's why you are seeing bad results.... or they didn't do anything.