Carburetor Issues??

[Garo]

Hi gentlemen, have an interesting one...  well to me anyway..lol. 83 NH 550, Bike would not start unless the choke was all the way on, take the choke off and it would die instantly, plus you could give it a little throttle and it would rev a little bit.  Turned the idle mixture clockwise as I was letting off the choke so the more I turned it the less I had to have the choke on.  so now I can start it with the choke off but I cant give it any throttle at all.  I give it throttle and it dies, now if I give it choke it revs up.. what the?  have a video.  thank you for reading!

[fishmeister]

The rail with the plungers is the choke rail. Does your throttle move that one?
Put a brighter light down there and post another vid while activating the cables. Don't have to start it.

[Garo]

no.  I wish that was the problem.  I checked for sure .  It just felt like thats what it was doing.  I was thinking of trying to make adjustments to the pilot screws.  Setting them back to their initial settings then going from there.  The book says 2 5/8 turns.  will try that.

[Garo]

ok, im thinkin I need new carbs.  I adjusted the pilot screws and the idle.  got it to start perfectly and idle perfectly without the choke.  Now I can give it just a tiny bit of throttle and it will only go up to about 3,000 rpms and I can hold it there but if I give it any more than that it chokes it out.  It cant be the plugs or spark if I pull the choke it can rev up to 8,000.  so that cancels that out right?  any carbs for sale lol... suggestions anyone??

[niteman]

I'm no expert on carbs, so take this as you will. It is very, and i repeat, very unlikely that you will need new carbs. My suggestion is to pull them and go through them thoroughly. It worked on my last bike, and I'm getting ready to do it on my '83 cb650sc.

You likely won't even have to separate the carbs.
-After you have them pulled, pull off the vacuum cylinder caps and the float bowl covers to start.
-From there remove the jets, needles, floats, gaskets, etc...and clean the insides thoroughly with rubbing alcohol and non abrasive materials like q-tips, cotton balls, and paper towels.
-Inspect the floats for cracks or leakage. Inspect the float valves and their rubber tips for degradation. Inspect the vacuum diaphragms for tears. Inspect the float bowl gaskets for tears or cracks. Replace worn parts as needed.
-Inspect the main jets and their sizes. from experience I know that the previous owner may have made the mains too lean or too rich. Cross reference the correct size in the manual. If you need to replace these, hey are cheap and can probably be sourced at you local dealer. 
-Blow low pressure compressed air through every nook and cranny and wipe them out again with the rubbing alcohol.
-Re-install all the bits and put the carbs back together.
-Get out your manual (which you hopefully have at this stage) and look up the pilot settings.
-Turn the pilot screws in all the way until they are lightly, I repeat lightly, seated.
-Turn all the pilot screws out to factory settings per manual (usually between 2 1/4 - 2 5/8 turns out).
-Ensure all the carb rail screws are torqued to spec per manual.
-Bench sync the carbs (if you don't know what I mean, do a forum search for Bumblebee's bench sync method...he is a god of carbs). Do this only after you have torqued rail screws properly.
-Reinstall carbs into the bike making sure to get all cables routed and mounted to their appropriate locations.
- Make sure that the carbs are tightly seated into the intake bands on the engine side (this can be a pain).
- Make sure that the rear of the carbs gets properly seated into the air cleaner bands.
- Your carbs should be like new at this point. 
You may have to adjust you pilot screws a tad, and also your idle screw to get it right. If everything was set correctly then your carbs are ready to go. If your still having issues then you may need to look at other areas of the bike. As the rule of thumb goes, an engine needs three things to run: air, fuel, and spark.

Good luck. If I can do it, literally anyone can.

[Garo]

Thank you for the generous reply! Better get off my bum and get to it!  oh and I did take of the back boots off the carbs to see in them and I noticed that the 2 left vacuum cylinders were down and the 2 right ones looked like they were stuck all the way up... normal?  once again, thank you. 

[Term]

With it not running all vacuum cylinders should be the down position.

[Bumblebee]

I noticed that the 2 left vacuum cylinders were down and the 2 right ones looked like they were stuck all the way up... normal?  once again, thank you.

Common problem caused by dried out fuel, oil vapors from the crankcase vent via the air box and accelerated by crapenol.

If you stick your finger in the carburetor venturi, you can push the slides up and they'll slide easily all the way up and down. If they're sticky or resistant at all, they need to be pulled and thoroughly cleaned. It's very easy to clean them.

[Garo]

alright, running much better.  thanks guys!  now its time to rebuild the clutch master cylinder.  The 650 and the 550's clutch master cylinder internals are the same right?? I asked this seller and he didnt know.. whats up with these 550's??  hard to find parts, always see the 650 and 750 stuff.  the guy at the bike boneyard never even heard of one..lol.  anyway it says that it will work for a cb650, so it should work for the 550 right??http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&_rdc=1&item=380166027341&ru=http%3A%2F%2Fshop.ebay.com%3A80%2F%3F_from%3DR40%26_trksid%3Dp4033.m38.l1313%26_nkw%3D380166027341%2B%26_sacat%3DSee-All-Categories%26_fvi%3D1&viewitem=thanks for the help guys you rock.  

[niteman]

Garo - glad it's running better for you man. That part number that you referenced above is th correct part number. When in doubt, find a site that has a parts fiche like this http://www.xtremeusa.com/fiche_section_detail.asp?section=123833&category=MOTORCYCLES&make=HONDA&year=1983&fveh=2958 and cross reference part numbers.

The cb550sc Nighthawk was only made for that one year so a lot of people that aren't familiar with Hondas from the eighties will have never heard of it. A lot of parts are interchangeable, and some aren't so just ask or cross reference.

BTW, I think I might order that master cylinder rebuild kit for myself. Thanks. 

[Garo]

nice, thank you.  very helpfull.  ordering now!  I cant seem to get pressure on the clutch.. no fluid is leaking from the slave, and I can hear a little hiss of air coming from the piston area on the master.. so I have it all apart waiting for the rebuild kit, now I can order yay!

[niteman]

nice, thank you.  very helpfull.  ordering now!  I cant seem to get pressure on the clutch.. no fluid is leaking from the slave, and I can hear a little hiss of air coming from the piston area on the master.. so I have it all apart waiting for the rebuild kit, now I can order yay!

Cool. Good luck. Hope it all works for ya. 

[Garo]

ok.  rebuilt the master cylinder, bought the bleeder kit.  bled all of the air out, still cannot get pressure.. its leaking something out of the bottom and I think its coming from the slave...lol.  time to rebuild that as well! should of just did that in the first place. I need a new master cylinder housing anyway, the last person smashed this one into something so bad that were the cap meets the housing is really thin. so if anyone has a extra master laying around 

[muttstang]

can anyone suggest a good video or how too site for pulling out the carbs and going through them?

[Bumblebee]

alright, running much better.

Got it running then? What was the actual cause? (Knowing the cause helps others out too)

can anyone suggest a good video or how too site for pulling out the carbs and going through them?

What better place to create a carburetor reference thread than here?
Post it up and there are plenty here who can help in general or with the specific motorcycle.

[Garo]

Got it running then? What was the actual cause? (Knowing the cause helps others out too)

I used some sea foam in the tank, adjusted the pilot screws, idle screw, took the caps off the top of the carbs and cleaned the vacuum's off.  thats about it..still has a strange throttle response.  When cold it boggs out,  but it runs good without the choke now.  If I let it warm up, I can rev decently for a while.  On another note, I cannot get the clutch to disengage.  I rebuilt the master cylinder, for the life of me I cannot get pressure.  I went to take out the slave...one of the bolts is broken off inside.     plus after it warms up, it starts putting out smoke out of the exhaust.  I took it around the block a few times to warm it up and test out the carbs and after about 10 mins it started smoking blue smoke...woooo buddy.

[B83550nighthawk]

Too much seafoam, but thats no biggie, run it a bit and top off the fuel, it will eventually dilute down and stop.

[Garo]

I already drained the tank and put fresh fuel in, but I was thinking that it could still be coming from the floats.  Didnt help that there is oil dripping from the slave cylinder right onto the exhaust..lol.  mmm smells good.    going to get some ez outs today to try and get that bolt out.  still if anyone has an extra clutch master that would be fantastic. thanks guys.

[Garo]

alrighty.  went to start it the other day and gas started pouring out of a breather hose under the battery...drained the whole tank.  ha back to the drawing board.  I could not see how that could happen.

[Garo]

allllllrighty.  had to put it off till after the holidays.  here is the latest video.   Thought I had it fixed! lol

[Brittles]

Have you checked your oil? Your engine is probably filled with gas.

[Bumblebee]

allllllrighty.  had to put it off till after the holidays.  here is the latest video.   Thought I had it fixed! lol

What exactly is that tube attaching to? It looks like it goes to the crank/transmission case. There shouldn't be a supply of raw fuel below the carburetors anyway.


Edit: I pulled up the diagram for the 83 CB55sc.
http://www.bikebandit.com/houseofmotorcycles/1983-honda-motorcycle-cb550sc/o/m1971
Look familiar? If so, that hose looks like the crankcase breather tube and the connection that the fuel is spraying out of goes into the crankcase itself. There should be absolutely NO gasoline in there at all. NONE. There's not even plumbing that would allow it to get down there even if something wasn't working right.

When is the last time you did an oil change? Who did it?

[Garo]

There should be absolutely NO gasoline in there at all. NONE. There's not even plumbing that would allow it to get down there even if something wasn't working right.

thats exactly what I was thinking.  how does gas even get down there????  but it did.  it was like a geyser shooting out of there.  I just pulled the float bowls off and one of the floats were stuck down.  the rest seemed ok.  tomorrow im going to change the oil out then.  but if that comes out of there, could the oil as well??  yikes.

[Bumblebee]

thats exactly what I was thinking.  how does gas even get down there????  but it did.  it was like a geyser shooting out of there.  I just pulled the float bowls off and one of the floats were stuck down.  the rest seemed ok. 

If it's doing the geyser routine, then there's little to no air in the crankcase and it's puking it out the only hole available.

I've worked on a few hundred engines over the years and have yet to see a 4 stroke engine where fuel has direct access to the crankcase. Two stroke, yes. Four stroke, no.

The only fuel into crankcase causes I can reasonably imagine are:
(1) A hole in a piston and a sunk float on that cylinder and the intake valve open and an unrestricted flow of fuel. (extremely unlikely)
(2) Major carburetor leak due to a sunk float that fills the airbox with fuel through the carburetor vent tubes then up to a level that the fuel backs up through the crankcase tube into the engine while the vacuum fuel shutoff valve is broken and letting fuel through. (bordering on runaway imagination but remotely possible in some ways)
(3) Major fuel supply plumbing screwup.
(4) Someone deliberately pouring fuel into the crankcase oil filler hole then left the gasoline in there. (Very likely since some people clean out engines with diesel fuel and some other people who only have a vague inkling of what the diesel fuel does will use standard gasoline thinking it's the same thing which it's not. Gasoline is not a good lubricant either)

Again, who did the last oil change and what were they doing?

tomorrow im going to change the oil out then. but if that comes out of there, could the oil as well??  yikes.

If that's the tube I'm thinking it is, my guess is that you will either get oil then gasoline, or all gasoline out during the oil drain hole. Change the oil filter while you're at it.

If you don't overfill the oil, no oil will come out that hole. Only crankcase air and oil vapors which is what's supposed to happen.

[Garo]

the guy I bought it from said he just changed it..but then again who knows.  the carbs were slowly dripping from the floats, really slow.  but when this thing started it literaly drained the whole tank of gas.  whats the tube that connects from the head to the crankcase???