Topic: 550 K0 carbs too rich

[DH]

I'll condense this as much as possible. 550 K0, with 022a carbs. 100 mains, 40 pilots (a little big, should have 38?)
stock 4/4 exhaust and genuine Honda air filter in stock box.
Good air plenum to carb rubber, rubber intakes hard, but acceptable, clamps tight.
Set float levels, polished float valves and seats, no overflowing of bowls. Carbs were taken apart and thoroughly
cleaned a few years ago, but was having the same problem as now, AND the
float valves were allowing overflow out of the tubes. Clear tube method confirmed.


What I have now: Bike is very hard to get started, lots of cranking, hot or cold engine. Choke makes things worse. Once it finally starts, it blubbers and will only
accelerate when throttle is slowly opened, and sputters faster as the rpm's increase. Exhaust stings the eyes. Plugs quickly blacken. no signs of carbs overflowing, hoses clear and no raw fuel inside of plenum. I used a harbor freight
lighted inspection camera, snaked thru the air cleaner box/air plenum chamber,
and was able to view the carb throats. Again, plenum floor is dry. With engine running at any speed above idle (when it would idle), and even during cranking, there appears to be a rather large amount of fuel being drawn from the float bowl at any given throttle opening. To me it looked like the needle jet circuit was coming on too soon and too strong, although I have no way of measuring or knowing what is too much or little. It is actually possible to see the fuel mixing with the intake air pulses. Looks like too much raw fuel, rather than a white mist type of mixture, and this may or may not be a problem BUT..... My pain in the a$$ question is this. Is there anything that would cause a rich condition that prevales throughout a carb's entire operating range that might cause these symptoms? Are the emulsion tubes easily elongated when driven out? I guess they go in only one way? Looks like the needle jet is part of the emulsion tube on these carbs. I find that 550 carbs pretty much suck compared to the 750 roundtops. These are makin me crabby...  rant over, and no more whining.....Anyone have any ideas? This is a weird thing

[goldarrow]

Stock 38 slow jets

[Deltarider]

Are the emulsion tubes easily elongated when driven out?

No. If the needle jets (aka emulsion tubes) don't come down rightaway after removal of the main jets, here is what to do.

Carbs can be left in situ. After removing the main jets
Twist the throttle at least halfway in order to raise the needles and then insert from below a match or wooden toothpick into the needle jets. When that is snug in the needle jet, cant or turn the wooden toothpick a mm or so and you can wiggle the emulsion tube out easily.
Some WD-40 at forehand can help.
Essential in this procedure is that you open the throttle to raise the needles.
Has always worked for me, but most of the times they just dropped after the main jets were removed. Very simple. And again: it can be done with the carbs in place. Keep the parts separate in containers or boxes 1,2,3 and 4 and make sure you assemble them correctly and not upside down. Check all little holes in the needle jets are open. It is important to check the little O-rings around the main jets still seal. If they don't seal well, raw fuel is happily sucked in by the engine. These carbs are easy to work on. No need to separate them from the rack. For maintenance removing the floatbowls is enough, the rest is to fill pages in manuals. Piece of cake.

Stock 38 slow jets

#40 slow jets or #38 don't make that much difference.

Did PO maybe change the needle clip position?

[dave500]

go right over your ignition first,check the resistance through the plug caps.

[DH]

Well here's where I am now. And thanks for the suggestions delta and Dave.. I'm  defineately going to use them...haven't taken the carbs off or apart yet, want to rule out everything else first.

 Measured plug caps, all 4 at 9000 ohms. None open, but all at their limit. substituted
caps from my 750 on the 550, as well as installed a better set of
stock ignition coils with better wires. A good thing, as both were needed.
Engine started easier, saw some improvement. timing and dwell check ok. Tennsioner should be ok, adjusted previously. Still won't run smoothly or rev cleanly
tho, so I did the clear tube method. Attached pics show where level is.
I then tried running the carbs out of gas (turned the fuel supply off) and noted that
engine tries to straighten out AS THE FUEL LEVEL GETS LOWER.
Note the pics and tell me what you all think. Is the level too high in the bowl?
As I mentioned earlier, when viewing the carb throats through the plenum chamber with my inspection camera, The carb began delivering a lot of fuel to the engine.
The process looked very "wet" and began very early, the needle jet spraying wet
raw fuel at the slightest opening of the throttle. I'll only ask because I honestly don't know, but how does the fuel level in the bowl affect the operation of the emulsion tube?

[lucky]

There are no "KO" carbs.
Who makes this stuff up?

[TwoTired]

Where are the pilot screws set?

Make sure the emulsion tubes are clean.

Check that the slide needles are in the 4th groove.

Us model CB550s were introduced with the 74 model as K0 022a carbs are correct for this model, 1975 was K1, 76 - K2, 77 - K3  My K0 74 has 40 pilots, too.

[DH]

There are no "KO" carbs.
Who makes this stuff up?

It's all an internet rumor started by a company in Japan called Honda. Perhaps you've heard of them?

honda-cb550k0-four-1975-usa_model

 

Where are the pilot screws set?

Make sure the emulsion tubes are clean.

Check that the slide needles are in the 4th groove.

Us model CB550s were introduced with the 74 model as K0 022a carbs are correct for this model, 1975 was K1, 76 - K2, 77 - K3  My K0 74 has 40 pilots, too.

Gonna have to pull the carbs again to check things. I have the mixture screws set at 2 turns out, my starting point was 1.5 turns out...I was the one who installed the #40 pilot jets, did it when I first got the bike. Gave the carbs a total cleaning
and replaced pilots because they were dirty and I had 40's as spares from my 750
laying around. The bike has been sitting for a few years, and is still running bad like when i first got it. I remember having a rough time driving the emulsion tubes from the carb bodies. Not knowing these carbs were different than the 750, I unwittingly drove the tubes out with a sharpened wood dowel, and felt the point go into the top portion of the tube while driving it out from the carb body. Its been nagging at me that I may have swelled/deformed the tubes at the top, possibly affecting their performance. Thanks folks. I'll post my findings...And while I have them out, what do you guys think of the fuel level  in the bowls represented in the previous pics with the red pointer?

[HondaMan]

#1 suggestion: change the 4 O-rings inside those metal castings that hold the carbs (and hoses) to the head. They are the same size as the ones in the valve caps, on your bike.
While you're in there, # 2 suggestion: #38 pilot jets. That difference of "2" is over 5% richer than stock, and these bikes already idle at 12:1 A/F ratio. It doesn't take much more to make them too rich! Then they don't start or run slow for beans.

[DH]

#1 suggestion: change the 4 O-rings inside those metal castings that hold the carbs (and hoses) to the head. They are the same size as the ones in the valve caps, on your bike.
While you're in there, # 2 suggestion: #38 pilot jets. That difference of "2" is over 5% richer than stock, and these bikes already idle at 12:1 A/F ratio. It doesn't take much more to make them too rich! Then they don't start or run slow for beans.

More great information. This forum has been good to me. Much appreciated!!

[lucky]

There are no "KO" carbs.
Who makes this stuff up?

It's all an internet rumor started by a company in Japan called Honda. Perhaps you've heard of them?

honda-cb550k0-four-1975-usa_model

I WAS a dealership mechanic at that time.
The term "KO" was not around at that time.

[DH]

Here's what I have now. Went ahead and pulled carbs again, removed emulsion tubes (ok, clean) and removed 1 carb throttle valve and checked 1 needle for clip
position (ok 2nd from bottom)....remaining 3 looked O.E. and unmolested ever...
Re checked all mix screws @ 2 turns out. Ok. Already had replaced intake manifold o rings, but checked ok. installed NEW #38 idle jets, It was mentioned earlier that carbs were equiipped w/#40 idle jets, but they were #38, so I must've put the originals back in at some point previously. But they were pitted and looked like $hit
so they got replaced with brand new ones. Meticulously adjusted float levels to 23 MM instead of 22. Reassembled carbs and installed just the carbs and throttle cable, but nothing else for test purposes only...........
Engine starts readily and revs/runs cleanly in all ranges....The thing even wants to idle on its own, before a vacuum sync has been done. Seems like when the fuel levels were higher, the cabs were delivering too much fuel at any given throttle opening, even tho they were'nt overflowing. This may be carb 101 stuff, but i actually learned a bit. The new #38 idle jets may have to do with the results too.
I don't have the greatest float gauge,(6" sliding "t" type") and my eyesight
aint what it was, so maybe that's got a little to do with it, but the lower levels defineately helped. Though not the root cause, The ignition checks and component replacements/substitutions probably helped, and were needed, especially for a good end result. Anyhow, that's what worked for me and how I arrived at my conclusion. Thanks to all for the suggestions and ideas, it really helps