Topic: CB550 Carb question

[sportz157]

I have been working on a 76 cb550 and one of the probs has been the carbs.  The bike would run but not idle.  So i took them off and cleared all the jets and soaked the carbs themselves in carb solution.  Well strapped em back on and on the first fire up...idle.  So i was very proud of that but what my question is is what should warm idle be at (rpm), also i am not 100% on this but i think the bikes running rich??? because it seems to only want to warm idle and the exhaust has a smoky look to it, not blue or white, but a dark heavy pollutant to it, how can i adjust to run leaner and is that possibly why it only wants to idle when warm?? Thanks for any help

Nick

[TwoTired]

CB550 idle setting - 1000  RPM  (I adjust mine to 1100 RPM)

Idle air bleed screws set to 1 1/2 +/- 3/8 truns from closed.

This assumes you have stock air filter and exhaust systems.

If your think idle mixture is rich, turn the Idle Air Screw out to lean it at idle.  Factory settings don't apply to modified machines.
If you turn them out too far, the low speed pick up with throttle will become wheezy and/or the engine won't pick up well.  Turn them back in with 1/8 turn increments until the throttle response suits you.

Did you synchronize the carbs or change the slide needle settings?
Is your air filter clean and clear?

[sportz157]

Ok Ill give that a try, a quick question on the air screw, are those turn counts starting with the screw all the way in, or just barely start it in after removing it and then screw those amounts. 

Also i have the air box, cleaner and manifold off right now and only one throttle cbale which i think is the pull?? its the top cable on the throtthle mechanism.  could all those be playing a significant enough role to be messing with my idle?

[TwoTired]

Turn counts from a seated condition. Don't over tighten as you can damage the seat and the tapered point of the adjustment screw.

Adjustments should be made with the bike in rideable condition.    These are fine tune adjustments and air filter, air box attachments offer restriction that effects idle, and run, tuning.

The cables don't effect tune, only run speed.

[sportz157]

Ok,

thanks for the help i really appreciate it.

NIck

[Bob Wessner]

As you fine tune the idle mixture, resist the urge to make big adjustments to the screw position. I was surprised to learn how small adjustments affect the idle mixture.

[Philly550K1]

if the idle mix is too rich, it would run worse warm, wouldn't it?  do you need choke to start cold?

consensus seems to be they all need a little throttle to "idle" when dead cold (if you set the idle screw when it's warm) anyway, what i read here. and\or a touch of choke for the first little bit......

-jc

[mgilvary]

Something to consider...

When I got my 75-550, it was running quite rich, and no amount of adjustment would cure it. Then I read somewhere on this board that the O-rings around the main jets can go bad, letting a much higher volume of fuel into the venturi. Indeed, my jet o-rings were worn and compressed. So, I bought a rebuild kit for my bike, installed it and immediately cured my too-rich condition.

[sportz157]

aright thanks ill have to investigate.

[Tim.]

The o-rings would be shot especially if you "soaked the carbs themselves in carb solution".  Did you dissassemble them first?  Did you take the jets out?  Carb solution will turn o-rings to sludge very very quickly.

[sportz157]

No, i took the jets out and whatever had the o-rings on it...although is there o rings within the carb body?  I took off the float bowl and the floats, and the pilot jets on each carb.. Am i ok...and i havent gotten around to messing with the carbs but it was running so sweet but since i put the air intake on and the box and filter the thing runs like #$%* again... hesitating, hard start, etc, is this because the screws are out too far?? 

Thanks,,


Nick

[Philly550K1]

it runs okay without the filter but not with it?  is this a pristine new filter, or one of unknown provenance? 

regardless, try another half-turn outward on the air screws (with this filter on) and see what you get.

and what was your answer on choke position for cold starts?

[sportz157]

For the choke, it is needed for cold starts, for the filter, its def a piece... i dont know how old it is but its falling apart, the metal casings have compltley separated from teh filter material, ive just been using it because the filter itself isnt all that dirty, its just old and falling apart. 

[Philly550K1]

have you run it with the airbox but no filter?  (just being, you know, thorough, here)...

[sportz157]

yeah it seemed to be a little better but still, its nothing like it was when it was under no restriction. 

[sportz157]

well ive been playing around with it for a bit and after a few turns of the screw, its running pretty good, my only question is there seems to be a liquid which i think is gas, ie smell and color, coming from the drainage pipe of the air intake manifold.  i dont have a rubber hose on there and i can see it dripping from the little spout its like the carbs are spewing gas out of the intake where the butterflys are, is that an indication of something?

[TwoTired]

Yes, your carbs are over filling and your fine tuning is for naught if raw gas is flowing into the intake runners.
Could be:
Float valve seat oring leaking
Float level set wrong
Float valve not closing completely.
Bowl stand pipe plugged
Carb drain tubes plugged

All this, times 4

Oh yeah, check your oil dipstick, if it is too full and smells of gas, you have oil contamination requiring a fresh oil change.

[sportz157]

wow thats depressing, will look into tomorrow.