Topic: Another Carburetor Topic

[Sporkfly]

Ok so I have work in 8 hours, I'm going to bed soon and am too knackered to use the search function (that's a lie, I used it, read a little bit, but didn't find what I was looking for). Just looking for some input.

I've got a 1977 CB550k. Here's the deal, I set valve clearances, set the points and have everything but the carbs sorted out to make it run. I hooked up my gas tank to the carbs and turned it over. It was only firing on the second cylinder. Anyway, I shot some gas into the carbs and turned it over fired right up no problems, which was an awesome thing because it was the first time I'd heard the bike do anything near running. Anyway, it died shortly after.

My thought is I'm not getting fuel to all my carbs. Would this be accurate? If it is what will I have to do to remedy it? Would float height have anything to do with it?

If I'm way off I'd appreciate some tips.

[martino1972]

so,you got this bike,and i guess it had been sitting for a long period,right??

-yeah,you want to take the carb's off,and take them apart,clean them good,lot's of topics here on how to do that,pay close attention to the idle jets,most of us ended up pulling the carbs a second or even third time to clean em right..
-new sparkplugs..
-read up on bench sync the carbs,you have to do that when your done cleaning the carbs and setting the float hight..
- start her up and drive away,

[Dave-and-his-550]

Make sure your fuel line is clear of any gunk. I couldn't figure out why my 3 and 4 weren't firing until I realized the bowls weren't gettin any fuel. Sure enough, I popped the line off at the tank to my inline fuel filter and it was all plugged up with some black stuff. I don't remember how it got in there.

But, if you have never taken off the carbs before, and the bike hasn't been ran in a long while, it is definitely a must!

I would unscrew the two outer float bowls (After you drain the fuel out by turning the drain plug) and take a look at the condition of em.

If they are pretty rusty then its time for a full carb clean 

I can give you a good tip on putting the carbs back in if you get to that point. I'll take photos to make it easier. Basically it goes like this:

Hook up the carbs to the cylinder intake boots, put in your airbox BUT have the rubber boots off and do not bolt the airbox up. Now all you gotta do is get the four airbox rubbers connected to the carbs and airbox. It's easy to push the airbox back enough to get the rubbers on the carbs, then just turn your finger around the rubbers to airbox end to get the lip of the rubbers into the airbox.

Have a friend take a foot and a half long piece of wood to leverage back the airbox, while you put on the two inner airbox rubbers, then the two outers. Worked great.

[Sporkfly]

My cousin had tinkered with this bike before he gave it to me. He cleaned the carbs and replaced all the o-rings. They're clean as a whistle. Checked just a bit ago and I am getting fuel to the bowls, but it's not getting to the cylinders? When I put gas in through the air intake she fires right up.

[dusterdude]

you have plugged up idle jets and maybe more.

[hymodyne]

+1 on checking the low speed jets

hym

[Sporkfly]

I really appreciate the input I'm not the brightest when it comes to carbs so being that there are 4 I'm sure this bike will brush me up on them once I tinker a bit.

[Sporkfly]

Thanks for the input guys, idles now! Haven't gotten the chance to let it warm up to try running it without the choke, but I had it idling with the choke. Now comes syncing them a little more accurately, hoping my charging system is in working order and then sort out these silly electrical problems, meaning I'll probably buy a new harness because there are splices and rewired things all over, somebody thought they could wire and made a mess of it 

[TwoTired]

If you find it won't idle without choke, it is probably you idle jets.

The 77K has the PD style carbs and the jets are pressed in.  It takes forceful determination to remove and clean them properly.  Doesn't matter how clean the rest of the carbs are, if these are not cleaned the bike will NOT run correctly.

You can usually tell which ones a clogged by the head pipe temps.

Cheers,

[Sporkfly]

The only carb rebuild kits (with all four) I can find on ebay are for 74-76 or I can spend $50 on a single kit for the '77 (meaning $200 to rebuild them  ). They're obviously different, but how different is different?

I probably will be avoiding spending that price obviously... I'm young and poor complete with university fees... Any tips on removing the slow jets? Only 1 carb was in need of cleaning, really. The others were clear and clean.

[TwoTired]

Unless the internals are damaged, you don't need to replace them.  Just clean them and reuse them.  Only the rubber parts need replacing if they are hard and won't reseal.

To pull the jet, I use a soft jawed parallel pliers, as this leaves minimal, if any marking on them.

[Sporkfly]

Yep, idles without choke now.

New problem though: She won't rev past 2000, cuts out as soon as I get the throttle to that point without fail. Carbs are 'coughing' a bit here and there. Carbs, points/advance unit, valves?

[TwoTired]

Describe your air filter and exhaust.

Generally speaking, the carbs are the last things to adjust/address.  All other tuneup list items should be addressed first.

Then there is the possibility of carb coupler leaks, and maybe carb sync issues.  Although, the later isn't normally associated with higher RPM problems.

Cheers,

[Sporkfly]

My air filter isn't pretty, but just as a test I pulled the boots off (meaning no air filter, I know, I'm a terrible person) and I had the same cut out problem. My exhausts are pretty decent, there are holes near the silencers but I had pressure coming out of all 4. My couplers are all tightened down pretty good, could it be an issue of torque at the intakes?

Some other information is I don't think my charging system is working, my battery up and died on me. Could that have something to do with not being able to hit the higher revs?

[Dave-and-his-550]

So you cleaned all the jets of your carbs correct? After you did that, did you bench sync the carbs before you put em back in? You certain your fuel is in good condition? (No loose rust in the tank) You bike should have a mesh filter in the tank, but they can get torn, and if you don't have inline fuel filters, then your carb jets can get plugged up all over again by small bits of rust.

I'm no expert, but maybe you do have a timing problem if the bike can't rev more then 2k rpm smoothly.

Also, how are your coils? Have you checked for a good spark on each plug yet?

[Sporkfly]

Cleaned the jets, they all cleared just fine. Bench synced. Fuel is brand new. The tank was lined with a POR-15 kit. Rechecked the points for the millionth time. New Dyna coils with healthy spark to each plug.

Every now and again the idle kicks up to about 2000 rpm with the choke on and at that point I am able to rev it higher.

[Dave-and-his-550]

Damn well, I dunno...But with the added information, I'm sure someone else can give a little more insight.

[Sporkfly]

More added info: Got it up to about 4k on choke, tried going a little higher but it just sounded/felt like it didn't want to.

[333]

Sounds like you still may have carb issues.  I have been riding for 30+ years, worked in the industry for 12 years,and have been preaching here for a while now.  It still took me 3 tries this spring to get my carbs CLEAN.  Normally I'd say to look at the spark plugs, but if you've been running a lot with the choke on, it won't read right.

Another thing to check is the spark advancer.  It's behind the points plate, and it means you will have to do the points over again.  But if it doesn't move freely, you'll never get the higher revs.

[TwoTired]

My air filter isn't pretty, but just as a test I pulled the boots off (meaning no air filter, I know, I'm a terrible person) and I had the same cut out problem. My exhausts are pretty decent, there are holes near the silencers but I had pressure coming out of all 4. My couplers are all tightened down pretty good, could it be an issue of torque at the intakes?

Some other information is I don't think my charging system is working, my battery up and died on me. Could that have something to do with not being able to hit the higher revs?

You mean it normally has a stock filter?

Tight band clamps are not insurance against coupler leakage.  Squirt WD-40 at the junctions and listen for a chan in engine speed.  If, you have a leak.

The spark requirement go up with the RPM.  And, low system voltage means low spark.

You have to fix the things you know are wrong one, by one until it runs properly.

Can you describe spark plug deposits?

[Sporkfly]

As for the spark plug deposits they were sooty on 1 and 2, but on 3 and 4 they were light tan/beige. I think that came with being on choke because the butterfly valves for 3 and 4 were flapping and 1 and 2 were stationary.

As for the stock filters, yes at the moment I have a stock air box. I just ordered pods and new jets however. This gives me more reason to take apart the carbs . I'll check for leaks at the intake.

[Sporkfly]

It wasn't firing on 3. I took apart the carbs and cleaned them again. It's firing on 3 now, but not 4 and I'm getting the same symptoms. Just not firing on one cylinder, but it's moving around on me. Don't exactly know what I'm chasing here.

When it wasn't firing on 3 I had Champion plugs in, I put my NGKs in and now it's not firing on 4.

 

[pablo78cb550]

I'm having similar problems. 3 and 4 are cold compared to 1 and 2 with seem to be working properly. i pulled the pilot/idle jets and ran them through my ultra sonic cleaner.
they looked blocked and then clear and then blocked. is there something moving around in there?
also i think two brass fittings are missing.
the first photo is how carbs 1/2 look. then the second photo is how 3/4 look.
see the missing brass fitting?
comments?

[TwoTired]

The "missing" brass fitting is the needle jet orifice at the end of the emulsion tube.

These tubes should all seat o the same depth.   You'll have to take them apart again to determine why they aren't the same length or what is blocking them from a proper seating position.

[pablo78cb550]

ok , i just found what part you speak of.
anyone with some 78 550 carbs lying around?