1983 Nighthawk 550 (CB550SC) Gas Leak

[Zaxeiler]

I apologize if this type of post has been placed before.  I attempted to search the previous posts, but the search feature is very poor at bringing up good results on the right page of the post.  But, here's my issue:

I just purchased this bike over the weekend.  It's in great condition and is a great ride.  It was sold by a man who collected nighthawks so it's in good shape considering the year, and has about 24k miles on it.  Besides the fact that it's my first bike, and I'm ecstatic and love riding it to death (even in the midst of winter), I have finally deduced tonight that it has a fuel leak.

So, as back story, I bought it about 120 miles from my home.  The deal was too good to pass up on, and I had a friend drive it back for me.  About 2/3 of the way through the trip, after about 70 miles she died on the interstate and needed to be changed to reserve.  Now, I had read that the range of the bike could vary from 80s-140s...  However, considering that we had been doing freeway travel and he had been riding in 6th (overdrive) for most of the trip it seemed unlikely we had been driving aggressively enough to burn through the 3.2 gal tank that soon.

So, sunday night upon return home, I filled her up at a gas station and began to practice riding around my area.  Monday and Tuesday I did some more practice riding, and considering I'm a new rider, none of it was very aggressive, no red lining, so I shouldn't have run though gas too soon.  Today (Wednesday) after a few great days of riding and 40ish miles (I reset the odometer after filling up) the bike died on me and I had to switch to reserve.  It was only at this time that I had realized she was leaking gas.  Each day I had been noticing a slight drip below the bike, but had assumed it was condensation coming from the bike since it was cold.  I hadn't realized that the bike had been leaking on the ride home, just thought we had gone farther than I remembered.

So, I understand that this isn't much information to go on.  But here's the spread.  The bike is dripping gas, I hadn't observed it too often, but this is a noticeable mark on the ground after it has been still for awhile.  I rode for 40 miles, so it can be assumed that I actually consumed about 1 gallon, which means that (if you assume something is left in the reserve portion) the bike has leaked about 2 gallons of fuel over the course of almost exactly 3 days.

I know that there's no way from this information that any of you can "know" what the problem is.  However, knowing where to start looking, or a few places to start would help me as a new owner.  If any of you with experience know something that is known to happen with a lot of nighthawks, or if from the information you can make a guess, or at least give any clues whatsoever, I would be most appreciative.

From one new NH lover to the others, thank you ahead of time,
Zac

[Laminar]

80 miles on the interstate isn't out of the ordinary. I typically see about 40-42mpg with mixed driving, but above speeds of 80mph on the highway, efficiency drops off drastically, I saw about 29mpg on one trip where I sustained 80+mph for 210 miles. I was filling up every 70 miles or so.

A fuel leak can come from a few places. First, make sure your petcock isn't leaking at rest. There is a diaphragm inside of the petcock that opens up the fuel when vacuum from the running engine pulls it open. When the bike is off, that diaphragm should be shut and zero fuel should get past it.

There is a gasket between each carb bowl and its corresponding body. These can age and leak.

The leak I experienced came from the fuel line and couplings between carbs. A single fuel line goes from the petcock to a "tee" that splits the fuel between carbs 2 and 3. There are aluminum tubes from carbs 1 to 2 and 3 to 4 that carry fuel to the outlying carbs. Each of those tubes and the fuel tee has a pair of O-rings at every carb connection. These get old, crack, and let fuel past them. I tried replacing them with similar o-rings from my local hardware store, but they weren't a perfect fit. I'd recommend getting the authentic carbs kits like this one. To get enough o-rings for the tee and both tubes you'll need at least two carb kits.

As far as appearing to run out of fuel after only 40 miles, did you look inside of the tank and confirm the low fuel level? When you went to refill did you have to put a full ~2.7 gallons in?

The petcock could probably use a good cleaning, as well as the in-tank filter. It's possible that there's debris and sludge inside of the tank blocking fuel from getting into the petcock.

[page62]

A good strong flashlight and a finger to check for damp spots should help you find the culprit right quick. If it's not the petcock, pull the tank and start checking all the fuel lines...
 

[detdrbuzzard]

if one ( or more ) of the floats in the carbs are sticking gas will overflow out the corresponding tube at the bottom of the carb. honda usually routs the tubes to the right rear of the engine

[Zaxeiler]

First thing first, thank you so much for all the replies.  It really shows what a great community you have here, and it extremely helpful to me, the new rider/owner/mechanic (which is where this seems to be heading)...

So, I'm going to reply first to the statements, and then give an update on the new "symptoms" I'm starting to notice, the more I come in tune with my bike.

I do understand that 80 miles on the freeway isn't bad, which is why I wasn't originally too concerned.  However, recent developments have made that seem less able to write off.  I've examined the petcock, and it doesn't seem to be leaking.  I've taken the advice of "page62" and started to do a cruel feel around for fuel.  It doesn't seem to be the links between each carb either.  I did fill up when I rode tonight and had to fill up 2+gallons, so she really was empty and not just clogged or anything.  And finally, from the last of the current posts, I don't know what types of symptoms would accompany a float operating incorrectly, but I have noticed some fuel leak tonight at the bottom of a carb, so "detdrbuzzard" may be onto something.

So here's what's new tonight...  The bike is getting worse, I road for around 2 miles tonight before noticing these new signs...  But here's what's happening.

I went and filled up the bike after running into reserve last night.  She did take 2+ gallons, I think about 2.5 so there really is some leak.  I began to ride, assuming that a short ride would get the fuel leaking again with the petcock set in its normal condition (rather than "off" or "reserve").  However, as I started to ride, at each successive stop (light, sign, etc.) I noticed the bike was struggling more and more.  With the weather, I assumed that I may had bumped the choke down or something so I tried applying more choke.  However, this did not bring the RPMs up as I assumed it would, but rather appeared to stall the bike (to even get the engine to run at this point the choke was all the way open, or down, and moving up to even as low as 1/3 choke cause the bike to stall).

So, the bike was running at around 1.5 RPMs max, and seemed to just be starved for gas.  Whether in gear with clutch, or in neutral there was no change.  Applying throttle didn't cause any problems (stall from flooding, etc.) so it seemed she was really short on fuel.  The engine was struggling so much that there was audible pause between strokes, and the headlight/speedometer/tach lights were dimming rhythmically.

Considering there may be a clog as "Laminar" suggested I switched the petcock while the bike was running between normal and reserve positions.  This made no change in the engine, still starving for fuel.

One more observation before I stopped was a slight clicking sound between my legs over bumps, etc.  This is not a high frequency clanking like keys on metal, but rather low frequency like two dense metals making contact (imagine two steel marbles making contact).

Upon parking, I gave an investigation as "page62" suggested.  This really was me just crudely feeling around for gas and smelling to try and locate the leak.  As "detdrbuzzard" hypothesized there was gas leaking at the bottom post/screw coming out of carb #2 (I assume based upon honda common service manual, the 2nd if looking at the bike from behind, and starting from left >right).

So, the bike is now struggling at stop, starved for fuel.  When I am riding there is a slight clicking/clanking between my legs.  And gas is definitely leaking from carb #2.

Your thoughts now?

Thank you so much for reading this long post,
Zac

[Zaxeiler]

Final observation:

So after letting her sit for awhile I went back out to observe and start the bike again.  It seems the bike suffers no difficulty in running in the first few minutes while she's warming up.  The choke/engine respond normally together (heavy choke brings the engine RPMs up and low settles the engine back down).  However, after running for a few minutes, and being throttled to replicate being driven (throttle up gradually, bring down, and back up, etc.) the engine begins to starve for gas again.  Only more throttle will alleviate the problem (no choke, petcock position, etc.).

However, this time out, I was more able to notice where the leak was more accuratly since all the lines were dry and became noticeably wet.  There is a gas leak dripping from the petcock.  It drips a drop about once every 10 seconds.  Also, the line that runs from the petcock to between the carbs (looks like a main fuel line that laminar discussed) is visibly soaked with gas.

Any comments are appreciated again,
Zac

PS - Tomorrow my Clymer manual arrives, so hopefully I can be more helpful with correct terminology, etc.

[OriginalHawk]

Hey buddy, welcome to the forums.
There is a mesh screen inside most petcocks, and over time they can become clogged with contaminants. Open yours up and ensure all o-rings look good and clean the screen and reassemble. From there you may have some fuel line, and then possibly an inline filter. If yours is the clear type ensure you can see fuel flowing through it. This is also usually a source or leaks, as the line can sometimes start to degrade a little bit. Check for moistness at all joints and ensure a tight fit.
As for the clicking/clanking sound between your legs it could be a couple things.
Do you only notice it on bumps?
If so there is 1 bolt holding your gas tank on, and there should be a thick rubber washer underneath there. Check to ensure your rubber piece is there, if it is not this could be the noise you are hearing.

[Laminar]

I tried applying more choke.  However, this did not bring the RPMs up as I assumed it would, but rather appeared to stall the bike (to even get the engine to run at this point the choke was all the way open, or down, and moving up to even as low as 1/3 choke cause the bike to stall).

This is normal. Once the bike's up to temperature, application of the choke throws off the mixture and causes the bike to stall.

And just to clarify the problem you're seeing-

Upon initial startup, the bike runs and rides fine, but after a few minutes it wants to stall or stutter as if it's starved for gas?

But if you give it throttle, it seems to run and ride okay?

[Zaxeiler]

"OriginalHawk" thank you for the advice.  I'll be sure, as everyone has prescribed, to check/clean the petcock first and from there move to the fuel line and carbs.  The fuel line and petcock are both definitely leaking, drips from the petcock and covering the fuel line before the carbs.  The carb #2 is also leaking from the bottom.  As for the clicking/clanking, I don't hear it on "only" bumps, but usually there for the most part, uneven ground, or even a quick rise and fall in a smooth road can cause it.

Laminar, thanks for all the help too.  I understand that choking the bike after it warms up will usually cause a poor mixture, however, the bike is reacting differently today than it was in the past few.  It now has to be completely open to even run, whereas in the past with the weather it's had to be at least at 1/4 position.  Finally, it's really the struggling of the engine that is troubling me, not so much the choke position, although it seems to be part of what's developing.

And to clarify, upon initial startup the bike runs, idles, and rides strong.  It then has a period where it has warmed up and will run with the choke much lower, and the engine runs, idles, and rides strong.  Up until today, this is where the bike would remain.  However, now, the bike then moves into a third period, only minutes later, where the engine seems to be on the verge of stalling, about as slowly as the engine could run without stalling (as if it's starved).  The choke has zero effect, until about 1/4-1/3 choke, at which point, the bike will stall.  If given throttle, the bike is fine, if I were to ride it with the throttle consistently turned ever so slightly (even in neutral/clutched) the bike would be fine, as if it's receiving too little gas (just by a little bit).

From my own description and the little that I know about car engines, I would guess one of two things, either the idle is set too low for neutral, or something is happening with the fuel mix and it's either too lean/rich and is causing the engine to slow.  In a final note about the engine running (aside from the fuel leaking issue) the weather has warmed significantly here.  Sunday > Tuesday the highs were in the 20s, Wednesday it was slightly warmer, and Thursday the high was around 40 (I doubt this change and the new engine function is coincidence).

I don't know if these new problems are related to the petcock, fuel line leak or not, but this is what I'm experiencing.

Your helpfulness is absolutely appreciated,
Zac

[Laminar]

I'm away from my bikes right now, but I believe there is a black plastic knob under and between carbs 2 and 3 that let you adjust the idle point. I seem to remember it being hard to get to. The next time the bike seems to want to stall, go ahead and turn that knob to raise the idle speed a bit and see if that helps. Just be careful not to burn yourself on the engine.

[Zaxeiler]

Laminar, thanks for all the help!  You've posted a few times now, and it's incredibly helpful for me when any of you all with more experience help.  As far as the idle/engine struggling, adjusting that knob definitely sped up the engine enough.  She's running beautifully now...  It's 48 degrees here right now, so I guess yesterday and today the air was just a little bit more dense and the mix in the bike was a little lean for oxygen, too rich in fuel.

Back to the leak though, somehow shipping got pushed back, so my clymer manual won't be here until next week but the bike is still leaking at a good pace.  I've noticed now that the drip is pretty regular, every few seconds, from the bottom of the petcock.  It's definitely leaking much slower (if not at all) when the petcock is switched to "closed."  The speed of the drip seems to stay the same when "open" or set to "reserve."  Also, as I've said, the main line from the petcock to between carbs 2 & 3 is visually wet with fuel.  Finally, from a leak of its own, or from the gas spilling along the main fuel line, fuel is also dripping from the bottom of carb 2 (although the main leak seems to be at the petcock, leaving these other locations much slower).

There've been some great comments suggesting to remove and clean the petcock, as well as check the o-rings in it, as well as connections between it and the fuel line.  However, without my clymer manual, as a new rider, I don't feel confident in just jumping right into that blindly...  Are there any other suggestions as far as easy fixes that someone inexperienced could do (something tightened, moved, etc.)?  Or is the job simple enough that steps could be outlined here?

Once again, I am so grateful for all the help given here.  It's a beautiful weekend for riding, so enjoy and be safe,
Zac

[Brittles]

If I were you I'd smell the oil dipstick for gasoline. You could possibly have a bunch of gas in your crankcase and that would be bad.

Sounds like a petcock rebuild is in order. It's not difficult at all.

[Snoopy]

If you can't see what you are doing take your lighter down there and flick your bic.  It might get  but take 

[Laminar]

Is the petcock leaking from the tube that fuel is supposed to come out of, or somewhere else? It almost sounds like the petcock isn't screwed tightly to the tank and fuel is leaking out of the tank-to-petcock connection. You can hold the petcock steady and take a crescent wrench to the bolt and make sure it's nice and tight.

[Zaxeiler]

Well, my Clymer manual actually arrived early.  So tomorrow I'll start the repairs.  I'll take pictures throughout so that if I make a mistake, hopefully one of you will spot it right away.  However, with all of your guidance and the trusty Clymer instructions, I feel confident in taking a look at the petcock.

While I'm working tomorrow, I will definitely check the oil to ensure that none has spilled in.  I know that would be catastrophic.  And the first thing I do tomorrow will be to check to ensure that the tank-to-petcock connection is snug.  However, assuming it's not quite that simple, here's the plan:

Drain the tank
Remove the tank/side covers
Disconnect the fuel lines
Disassemble and inspect the rubber elements of the petcock
Inspect the fuel lines between all items (tank, petcock, carbs)
Reassemble the petcock with a little teflon tape
Reconnect all the lines
Reconnect the tank
Ride with no problems (optional, dependent on the bike)

If you see some error in this set of steps, or if you want to add a step please give me a shout sometime before tomorrow afternoon.

However, this is all I feel qualified to do, I don't know if I have the ability yet to work on the carbs (possible removal of the bowls and inspection of the floats, but nothing more).  So, with me the best of luck and I'll upload some photos after tomorrow, hopefully of me riding more than anything!

Thanks for all your help, I'm sure I'll have more observations tomorrow,
Zac

[fishmeister]

Don't think the teflon tape is necessary due to possible contamination. Just tighten the nut well as earlier noted. Be sure the tiny o-ring is there and in good condition. Fig. 8 (1.3 x 10.6)

[Zaxeiler]

So today I worked for about 3 hours on the bike.  I removed the side coverings and the tank.  After draining the tank I removed and examined the petcock.  Opening up the vacuum assembly didn't show any problems, the gasket was in good shape and sealed well.  Furthermore, the bowl at the bottom still had a screen in good shape.  I reassembled the bowl with the slightest teflon tape (sorry Fishmeister, I hadn't seen your post).  Also, I reassembled the vacuum assembly with a slight amount of gasket sealant.  Finally, the top stem, filter, and o-ring needed to be realigned.  I replaced the o-ring and centered the filter again.

Finally, when reassembling the bike, I replaced the fuel line from the petcock to the carbs.  I figured a new reinforced line with some fresh clamps couldn't hurt.  The vacuum hose however, I did not replace as I wasn't noticing any problem with the suction from the engine before.

All in all, she's running well again.  However, to get the metal to seal well on the petcock assembly I had to rotate the center piece of metal.  For instance, when you remove the 4 screws to look inside at the gasket the outer piece where the vacuum hose attaches remains unchanged, but the next layer down, the piece of metal with the small opening (to let outside air in, I assume) I rotated 180 degrees so that it now faces up.  Trying to understand how a petcock functions, and since this small opening does not connect to a specific line or anything, I didn't think this would change anything.  Doing this just gave me the best seal possible, as the metal on the petcock had been torqued/warped and no longer laid flush in the other orientations.

So, she's no longer leaking, and is running beautifully.  And you all are to be thanked.  So thank you for all the aid, hopefully I can contribute to this board in some way to show my appreciation.  But if not, my riding tomorrow will speak volumes about it.

Zac

[Laminar]

Judging by the picture in your avatar, your handlebars have been replaced at some point in time. The stock 550 handlebars are taller and have a lot more pull-back. You can see that the mirrors jut inwards before going out, and when the handlebars are centered, the clutch and brake fluid reservoirs are at an angle.

This doesn't necessarily pose any particular risk to you, except for limited visibility because the mirrors are pulled inward and your cable elbows might come into contact with the tank at full steering lock.

[OriginalHawk]

Hey Zac, great job on getting things squared away.
Feels great, doesn't it?
Upon reassembly did you notice that rubber piece under the gas tank I noted earlier? If not that could be the source of your clunk.
A couple things to note if this is your first real experience with owning a motorcycle..
Check your tires to be sure they are inflated properly, and have good tread. Check your tires for small cracks or dry rot along the side walls, if you see these it means that the tires are hard as rocks, old and should be discarded EVEN IF they have plenty of tread.
If you haven't done so already, change the oil and filter. Never know when it was done last.
One thing I like to do on any vehicle with a carbuerator is add "Seafoam" to the gas tank. It will help clean your carbs of varnish and generally help it run a little better. It is available at Autozone or nearly any auto parts store.
One more thing, underneath the bike towards the left side you will see a capped hose. You may have to look for it a little bit, but park the bike in the class and let the bike relieve itself. Lots of stuff may come out if it has not been done in awhile.
Ride on Zac, any questions feel free to ask us..

[Zaxeiler]

I forgot to post, here are some pictures if any of you are interested in seeing the petcock condition:
http://www.facebook.com/album.php?aid=2032058&id=1197300068&l=2cd06759f5

Laminar, yes the handlebars were replaced.  The previous owner told me that he didn't like the older "ape hanger" look.  Actually, the mirrors are probably the next project on my bike that I need to take up.  My view is limited to a certain extent, not dangerously, but I would prefer to have a wider angle to give me a 100% complete view of the lane behind me...  If you know of any sites for nighthawk parts let me know, as for now http://cyclepartswarehouse.com/ is the only one that I've seen suggested.  And if I turn too sharply when backing up or rolling around slowly the cables and bars come in contact with the tank, but I have to turn really sharply for that to happen, so really the mirrors are the only problem.

OriginalHawk, it absolutely does.  I've never basked in the success of repairs like I did yesterday (even knowing how small they were).  I still haven't noticed the source of that sound, although the rubber does still remain for the tank bolt, so I don't think it's that.  It's somewhere from midbike > forward, although I'll admit, I'm having a hard time narrowing it down since I have to be riding for it to make the noise and hitting some bumps (I'm trying to use an old cobblestone road by where I live to make it more noticeable).  I've tried holding different things while riding to isolate the sound (it's not the keys, headlight, petcock, etc.)  Along with the mirrors, this will definitely be my next project simply because it's annoying and has me curious/worried.

The tires are good, I inspected them when I bought the bike.  No dry rot, and tread seems about mid life.  The oil level I checked and it was fine, I'll probably change the oil/filter in the spring, the previous owner claimed he had just done it before winter.  What is this "Seafoam"?  I seem to see people recommending it all over the internet for carbs/tank cleaning.  It carry a risk for any engine damage does it?  I saw the capped hose yesterday when I was unhooking the battery leads, it ran next to the hose for the battery.  What exactly is it?  From your description it seems to have some waste, but where does it run from?

Thanks for all the comments again crew.  Happy riding,
Zac

[hppants]

What is this "Seafoam"?

It's a high grade fuel stabilizer.  90% of the gasoline you buy now contains at least 10% ethanol (alcohol).  Our bikes were not designed for this.  Of course, most bikes don't get ridden every day, so Seafoam keeps the fuel from breaking down, causing varnish and other problems in your carbs.  I was skeptical, but there is no doubt, it works.  My bike idles better and the fuel mileage is increased.  I add about 1 oz. per gallon of gas unless I'm riding all day and refilling on the go.

[Brittles]

The oil level I checked and it was fine, I'll probably change the oil/filter in the spring, the previous owner claimed he had just done it before winter.

Best to go ahead and change the oil and filter now imo..........you don't know 100% if the po was totally on the up and up or not.

[Laminar]

  What is this "Seafoam"?  I seem to see people recommending it all over the internet for carbs/tank cleaning.  It carry a risk for any engine damage does it?

Used properly, there's no real risk to using it. I think they recommend a very small amount per gallon of gas, but I've put as much as a half can in a 3 gallon tank without any negative results.

I saw the capped hose yesterday when I was unhooking the battery leads, it ran next to the hose for the battery.  What exactly is it?  From your description it seems to have some waste, but where does it run from?

A certain amount of the air/fuel mixture in the cylinders gets past the piston rings and into the crankcase. To prevent the crank case from pressurizing and exploding, gases are vented into the airbox to be reburned. Some of that vented gas condensates in the airbox and drains to the bottom. Uncapping the hose will let oil, gas, and other fluids drain out.

[Zaxeiler]

That seems like a great product, I just didn't know if it was harsh enough to use on a 27 year old engine...  I did end up buying some today from autozone.  I'll probably throw it in tomorrow before riding (seems like it takes 10-15 minutes to clear stuff out and I won't ride anymore tonight).  According to their (the company's) youtube video and the bottle, it seems like you can pour it in most every part of your bike.  Do you suggest I add some to the oil too?  Or just the fuel?

I'll definitely get to changing the oil soon.  You're right Brittles, you never know if it's really been awhile or not.

And for the capped hose, I'll open it tomorrow.  I can't seem to find it in Clymer's, but do I need any tools?  Is it a screw cap?  Or should I just be opening a clip or something?

Finally, I need your all's advice on finding parts for the bike...  Besides going to a dealership and having them order them (at great profit) I was wondering if you know any online/regional bike parts stores.  I'm looking for something along the lines of an Autozone.  However, some things on my bike need replaced like mirrors, kickstand rubber, and one of the chrome caps that go on the sides of the frame near the foot pegs.  If you have any thoughts, please post them.

Thanks for the excellent advice,
Zac

[fishmeister]

Most all real parts are dealer or online....

http://www.cyclepartswarehouse.com/fiche_select.asp

http://www.cyclepartswarehouse.com/fiche_select2.asp?category=Motorcycles&make=Honda&year=1983&fveh=2949

Then of course there's always e-bay.