Topic: '78 CB550 Starting issues

[chstr1]

My CB559 bike is impossible to start when the engine is cold.....even if the temp is 70 degrees out.  Currently it is in a garage that heats to 40-45 degrees but the issue is the same as I had all last summer.  I had some tips earlier  from this forum that have helped, because now the choke butterflies close all the way.  The cable had a break and wasn't closing more than 25%.  The guy I bought it from never told me, so I spent a good deal of time figuring out how to get it started.  But now, I still can't get the bike to start unless I pull the airbox and use a piece of cardboard to cover the air intake.  Then it will fire and eventally start.

I let it run at high idle till warm and then it runs well.  My only problem is getting it to start without covering the air intake, and that is too much hassle. It appears it must be an air mixture issue because it just doesn't fire until cover the intake.  I am trying to get it starting correctly over the winter so I'll be good to go when the weather warms.  Any more ideas out there.  I much appreciate the knowledge you share.

[TwoTired]

I'd have to guess you are still having choke actuation issues as covering the intake does mostly the same thing as full choke application when it is properly adjusted and working right.

I'm looking at a spare clunker set as I type this.

Have you actually seen the butterflies fully close?  Or, are you going on travel limits to assume full actuation?

Have your carbs been worked on before?  There two butterfly shafts interconnected between carbs 2&3.   If this interconnecting union wasn't reassembled correctly, you may not be getting full closure of ALL of the butterflies.
Also, application of choke change the idle setting by moving all the slides a bit open.  If there is a nub on that cam it would feel like a choke stop and prevent full closure of the choke butterflies.
Perhaps, applying a bit of twist at the throttle during choke knob application would increase choke transit?

You might have to the remove the air box and plenum to verify full choke butterfly closure on all carbs if you can't see in there with lights an mirrors.

Cheers,

[Kelvin8]

Your slow speed jets may be clogged, or at least partially clogged. Blow some carb cleaner backwards through the jet to clear it, you should get a strong stream coming out, not just dribbles or a gurgle. I've got the same bike and had problems starting (even after the carbs were supposedly soaked clean). I got them cleared out and it starts up fairly well now, the carbs still need balancing.

Kelvin

[chstr1]

Thanks for those suggestions; I have gotten lazy and not attended to the problem for awhile.  I thought I had the butterfies fully closed, but being that I do need to turn the throttle for them to fully close makes me wonder if they still need work.  This bike had only 18,000 miles when I picked it up last spring, so I think everything is original, and doubt anyone has tinkered much with the carbs. 

What does Kelvin8 mean when "blowing carb cleaner backwards"?

Also, what is the significance of the adjusting screws that face down on the back side of each carb?  Are these the air intake adjustments? I have the Clymer manual, but find that as worthless as toilet paper in a thunderstorm.

[Bob Wessner]

What does Kelvin8 mean when "blowing carb cleaner backwards"?

The jets protrude down from the carb body into the bowl area. I think he means drop the bowls and spray some carb cleaner upward into the openings of the jets. You might get lucky and it will work otherwise you may need to pull the carbs and give them a proper cleaning.

[cntrhub]

"I let it run at high idle till warm and then it runs well."

Some are not reading what you are posting. Try never to mess adjusting with the carb screws. You are not having any kind of problems but getting the choke to work.

You said the bike "runs well."  That should settle any kind of carb clogging problem with the bike. If a bike idles, can take throttle through the gears, then nothing is clogged. Please, you do not want to mess with the screws on the carbs. Leave these alone even if the bike stops dead. It is usually never a problem at the screws. Those screws are preset and never need to be adjusted unless a (full tear-down) service to the carbs are needed.
Fix the choke cable. Go to a lawn mower shop and buy a universal cable assembly. Pull from a donor if aval.

Here's the hard starting deal. It's cold out. Molecules are closer together. The engine needs more fuel to match the colder more compact air. Your fuel ratio is off. It's that simple. Choke the bike to start. When it starts... do that same warm-up routine you've been doing to get it running.
Go out there now and do it. Gas looses it's oomph in about 9 months. It will varnish if left for longer periods. Drain the gas in the tank, put it in your car. Get fresh gas and put it in the bike. Start the bike up with fresh gas. If it still idles, you are ready for the warmer days. Keep burning the gas in the carbs. Let the fresh fuel from the tank run in there as weeks go by.
 

[chstr1]

Thanks; you sorta confirmed what I have been thinking.  If it idles ok, and starts with the air intake covered, how could it be a carb problem?  I am going to focus my effort on being sure that choke is fully closed.  Ironically, I emplied out my gas can and bought fresh regular gas yesderday.  I want to eliminate the bad fuel possibility, although all last summer it had starting problems.  I am 95% sure that was related to partially open butterflies.

Is it possible to have a choke cable too long? I had to tack it onto the throttle cable or else there was too much "give" and the cable would not pull the choke closed. 

[cntrhub]

If that was the final fix, then no matter what length, you still need to get full close, and full open with the cable. Other than being too long, who care?... It made it work.

[fhoffman]

The Haynes manual isn't very much more useful for the CB550.  it is primarily written for and photographed with the CB400.

[Kelvin8]

By backwards, I mean in the opposite direction of normal flow, so the cleaner should be coming out of the orfice in the bowl, not going into it. When you take the carbs off (PIA) when you look through them in the direction of air flow, you'll see two brass tubes facing you, the one on the left is the slow speed circuit, blow the cleaner through that one, you need to get a strong stream coming out of the intake (or bowl) side of the circuit.