CB550 - Wont idle, cold cylinder

Alright, i have been wrenching on this bastard for the better part of three years. she ran today, but wont idle. overall, very happy day. but now, i have the taste for blood, sort a speak.

kicks over relatively easily, wont idle though. cylinder 1 is cold (header), 2-4 are about the same heat level. see the video.

http://youtu.be/FUMbMv6rxTM

let me know what you think!

Put some clear fuel line on and make sure the carb for that cylinder is getting gas. Next look in the manual to make sure you have the carb adjusted correctly plus some for those open pipes. Before all that make sure you have spark on that cylinder's plug.

thanks!

spark to all cylinders.

with regards to clear line, do you mean the overflow lines? carb 1 and 2 are on the same line, so if two is getting fuel, one should be as well.

would the pipes make it not idle at all, or just make it idle like shit? i have a set with baffles, but i have an exhaust stud issue that is holding things up.

also, i am getting some smoke out of the breather on top of the engine. not a lot, and not constant. white smoke.

is that okay?

Very common on an engine that hasn't run in a while. It should go away within a couple of hours. It's just water steaming out of the cases. If you use a clear breather hose, you can watch it condense on the inside of the hose after a little while.

Not idling and idling like shit are about the same things....

Yes the cut off pipes will effect things massively, and not for the better
Cant tell in the pictures if you are running pods. SOHC4 bikes HATE pods, even more so when talking about cheap emgo crap.

Lests start with the basics
Do you have a factory manual? If so read it and go step by step through the tune up section
Have the carbs been cleaned? What jets are in there? If its stock you need to buy jets. Before we get into that, there is no answer to the "what jets do I need" question. Buy two or three complete sets and tune. Pods and cut exhausts is not a performance upgrade, so you are going to have to try and tune out the power losses of these "mods"

Check for air leaks after everything else is set

breather smoke is normal for a while

thanks surffly.

running stock airbox, but it is off the bike right now. 4-1 is stock, but the muffler is off it. i am going 4-2, but ned to replace a broken exhaust stud (god knows how).

jets are stock, but new. bought oem stuff. no air leaks.

i will reinstall the airbox, and try to figure out the exhaust.

keep the suggestions coming. i will be working on it all day tomorrow, and keep you guys posted.

My cb550 idles quite perfectly without exhaust (yes, no exhaust) and no filters on a testbench. Carbs used were OEM and had OEM parts. Airbox helps a lot, but exspeccialy on high revs. No idle sounds to me like clogged idle jets or wrong settings of airmixture screws? Could also be your needles are to high. Try putting them in the middle of the 5 options.

I'm gonna second the clogged jets (or clogged valve), or possibly incorrect float height. I once put a float in upside down without realizing, that didn't work too well. Will disagree with comment about SOHC bikes and pods, however. Sometimes a rejetting is in order, but sometimes not, and, of course, much to do with exhaust. If it's a float or valve problem, when you pull the float bowl it'll be dry or not have that much gas in it. If it's full of gas, it's likely the idle jet.

clean the carbs, very thoroughly. floats are all even, all four cylinders fire now.

Took off the manifold, and gave them a good cleaning, and soak in seafoam. replaced the o-rings (also replaced the o rights for all tappet covers). made sure all connections where as air tight as possible.

she fires, and seems to run a little better when i rev, but as soon as i let go of the throttle, it dies.

any suggestion is welcome! [perhaps some more info on idle jets. since all 4 cylinders die, would that mean all 4 jets are faulty?)

thanks everyone.

Idle adjust screw? I.E., idle RPM too low to maintain idle? Or likely mixture. What do the plugs look like?

carnivorous chicken said:

Idle adjust screw? I.E., idle RPM too low to maintain idle? Or likely mixture. What do the plugs look like?

Click to expand...

I thought of that as well... The idle screw is located under the tank, at the right side, opposite of the petcock. It's mounted on the carb rack. Start the bike with throttle and screw the idle adjuster in till revs come up. Now, let go of the throttle and screw the idle adjust screw back in untill she's around 1200 rpm. 99% of the time it's something stupid if all obvious options have been checked

DO NOT adjust the idle by adjusting the throttle-cables. It's dangerous as the cables might get pulled on when cornering. Always have some slack on all cables when not operated. Extends lifetime by a gazzilion years aswell...



Its part 2 on the diagram btw;
http://www.cmsnl.com/honda-cb550k3-four-usa_model1015/partslist/E++17.html#results

i have the fuel air mixture screws at 1 1/4 turns out. factory is 1 1/8. seemed to help with starting. such a small turn, this would probably not prevent the idle, correct?

spark plugs...... see attached.

Hey Bert..... i cant do this, i have to be actively revving the throttle in order for it to stay on. i have adjusted the screw in a turn, then start. in another turn, then start...etc.... i set the throttle slides as per the manual, so i was hoping that would be accurate (or off by a turn or two), but no luck. i will fiddle with it more tomorrow. making a list now of things to try.....

Adjust the idle speed screw to raise the slides far enough for it to fast idle.

Those plugs don't tell us much but they appear to be DR plugs with inbuilt resistors. If your plug caps are standard resistor types that would potentially be a problem. Try to get some non resistor plugs D7ES or non resistor caps.

What year CB550? '78 with PD46 carbs have smaller jets (90 main, 38 slow as opposed to 100 main and 40 slow) and depend on the very restrictive muffler and stock airbox to run right. This was an emissions thing back in the day. Does choke change anything?

Sounds like my CB500 starting for a while back....
1 header not heating up, means no action there
If you have a spark it could be carbs.Something as simple as float level, or a clogged idle jet.
But also ignition is tricky, sometimes the spark is "good' when you have see plugs out of the engine, but what happens inside "under pressure" is a different thing. Probably when you have the original coils, they are about 30 years old, as are the cables.....

I have eventually ultrasonic cleaned the carbs, used a complete revision set, with all new needles jets etc end mounted an electronic ignition with 3 ohms coils and used new cables.
Now it's better, still not 100% but that is mainly due to a home meade exhaust and not original airfilter.

johnnynogood said:

Hey Bert..... i cant do this, i have to be actively revving the throttle in order for it to stay on. i have adjusted the screw in a turn, then start. in another turn, then start...etc.... i set the throttle slides as per the manual, so i was hoping that would be accurate (or off by a turn or two), but no luck. i will fiddle with it more tomorrow. making a list now of things to try.....

Click to expand...

You should turn the idle screw when the engine is running. Screw the idle adjuster to the point where it makes the revs go up, higher then when you would manually rev it. (Not for too long obviously )
Then screw it back in again (Don't fiddle with the throttle no more!) till it idles nicely. Then rev it and check if it'll still idle nice. You can not ever adjust the idle adjuster when the bike is not running, that makes no sense at all.

johnnynogood said:

i have the fuel air mixture screws at 1 1/4 turns out. factory is 1 1/8. seemed to help with starting. such a small turn, this would probably not prevent the idle, correct?

spark plugs...... see attached.

Click to expand...

I'm not sure if you think i mean the fuel-air mixture screws - as i don't mean them at all. There is one big fat adjuster wich is supposed to screw by hand. Look at the picture an tell us if you turned that one. No need to fiddle with the air-fuel screws. just set them 1.25 out and that should be ok. Adjustments to those screws are only helping when the bike is on a dyno or with syncing. There's no need to fuck with them 'on the fly'.

Can you let the bike idle with throttle handle in a fixed position or do you need to rev it constantly?
If you need to rev it up all the time, the bike has some starvation of air or fuel. Revving the bike helps with the starvation, but only for a short period of time, making you have to rev it again.
Try to let the bike idle around 1200 rpm with a fixed throttle position, or even better, with the idle screw.
Theoraticly you could detach the throttle cables and let the bike idle with the adjuster screw alone. Please let us know if you understand and tested that, otherwise i'll be poking in the wrong direction

edit;Teazer's spark-plug tip as a good thing to check aswell - buy some simple caps without any condensers or shit and test the bike again.

edit; How many miles are on the bike? You know, your carbs could just be dead. Worn out and not accurate anymore. In that case, even a GP mechanic would not be able to fix it.

run down some updates before i go kicking again.

- i have not touched the throttle cable, only turning the actual throttle and adjusting the idle screw.
- carbs are fine, not shot at all.
- i have checked the coils and wires, they tested fine, whatever that means...
- new caps (need to confirm the resistor situation ( with regards to the caps. i need one of them to be a 'resistor' type correct? but not both? so either the caps or the plugs, but not both or neither?)
- have to be constantly revving. it will not idle at any RPM level, or any amount of throttle. i will examine the starvation issue.
- i have the stock headers on, but no muffler. i will attached the stock muffler.

could there be an issue pertaining to the clutch?

for reference, 1976 CB550F