CB550 - Wont idle, cold cylinder

[teazer]

Did you say that even if you hold the throttle slightly open, it still will not fast idle? What about at 1/4 throttle? It should rev pretty high with no load and 1/4 throttle, so don't do it for more than a second or so.

When you cleaned the carbs/jets did you check that the pilot jet outlets are clear? That's teh tiny drilling through which the air-fuel mix from the pilot jet discharges into the throat of the carb. Typically they are less than 1mm diameter and they tend to clog up with fuel deposits and corrosion.

I always blast carb cleaner through all the drillings and I check one carb against another to see that they are all more or less the same.

 

[johnnynogood]

correct, will not idle. only stays on when i twist and the throttle. i can back it off a bit, but need to rev it again to keep it from shutting down....

i was hoping it was in first gear or something, lol. but it is not.

 

[surffly]

Do you have a factory manual?

 

[johnnynogood]

yes, i have the factory shop manual.

that is what i used to clean and tune the carbs.

 

[surffly]

So now use it to go through the tune up

You can not make assumptions about what is right and what is wrong. There clearly is an issue with the bike.
Start at the beginning and work your way through the bike.

 

[Tetter]

Have you cleaned the carbs ultrasonic ?

How are the tips of the airscrews ?
There are many stories known about screws which have been screwed in to far, and while doing that, damaged the tip, or even broke them of.

 

[carnivorous chicken]

Hard to tell from photos, but those plugs look fouled. Possibly carbon fouled (too rich) but possibly oil fouled (rings, likely). They certainly look old (I can see some rust). I'd try cleaning them with a wire brush and setting the gap again. Or getting new plugs. If you've got spark, it's almost certainly not the coils -- they're usually not the cause if you can see spark. How are the points? Clean? New?

 

[Bert Jan]

As the bike runs and revs, my money is on timing then. Is the advancer doing its job? That might cause the need to rev as the timing might be fluctuating?

 

[Bert Jan]

Is she running on all 4 now btw? Camchain tension ok?

 

[johnnynogood]

cam chain is good.

yes, running on all four now.

i st the timing, and checked it about 3 times over the past month..... i can keep messing with it though.

 

[johnnynogood]

Have you cleaned the carbs ultrasonic ?

How are the tips of the airscrews ?
There are many stories known about screws which have been screwed in to far, and while doing that, damaged the tip, or even broke them of.

air screws are good, new OEM ones. tips are good.

 

[johnnynogood]

So now use it to go through the tune up

You can not make assumptions about what is right and what is wrong. There clearly is an issue with the bike.
Start at the beginning and work your way through the bike.

thanks for the advice. However, i have done this, and cannot locate an issue.

i am thinking it has to be combination of a couple small variances, because everything has been set as per the manual.

 

[johnnynogood]

Hard to tell from photos, but those plugs look fouled. Possibly carbon fouled (too rich) but possibly oil fouled (rings, likely). They certainly look old (I can see some rust). I'd try cleaning them with a wire brush and setting the gap again. Or getting new plugs. If you've got spark, it's almost certainly not the coils -- they're usually not the cause if you can see spark. How are the points? Clean? New?

plugs are new, never ran, except during this testing process. i have replaced them though, since i had a second set on hand.

no points, electronic ignition.

 

[teazer]

Curiouser and curiouser cried Alice.

Let's take Bert's suggestion and explore that. What electronic ignition is fitted and does it use the mechanical advance or an electronic advance? Did you set timing statically and did you check it with a strobe to see if it advances smoothly and correctly? At 3500 or so rpm is it lighting up the advance makes at 1-4 and 2-3 correctly?

 

[Bert Jan]

Hah! Now he tells us he has an electronic ignition... Whats next? bored to 968cc? just kidding!

Electronic ignition is far better then points due to various -known to all- reasons.
Only disadvantage is the fact it has to be SPOT ON. Where points are a little forgiving, electronic is not.
Points are ok to set by hand/staticly but when you set a electronic ignition you NEED a strobe to set it tight.
Like Teazer said, are you using the OEM advance system or something that came with the electronic kit?
If you still have the points and half an hour, i would replace them and check engine. Just to check if it's indeed the ignition. If so, buy a strobe and you're good to go

 

[Bert Jan]

- i have not touched the throttle cable, only turning the actual throttle and adjusting the idle screw.
- carbs are fine, not shot at all.


for reference, 1976 CB550F

You state the carbs are ok (not shot) With all respect, there's no way to check that for sure. Carbs have a lot of variables and a little goes a long way.. For example;

I have a 76 550 and rebuild the whole bike, incl carbs. Used new OEM kits and all. Kept leeking and doing shitty. Wouldn't run great either. I cleaned them ALL THE WAY more then 10 times, to no avail. I set it as best as i could and called it a day.

Last month i bought a complete 550 for 50 bucks. Bike was parted and stalled for 5 years before i bought it. I took those carbs, put them on my bike with no cleanjob, filters or adjustments and the bike runs better then ever!
I now have pods on them and it's ridiculousy faster and better responding then the other rack.

Conclusion; Carbs can look nice inside and out, but there's really no way to tell for us amateur carb-techs. If you have a rack that you know works ok, put it on. Remove all variables and work your way to the problem.

edit; Now, since we now know you have an electronic ignition, fiddle with that first

 

[johnnynogood]

got my new dyna ignition in the mail. trying to set the timing, and having issues. it will not get to full advance. i searched this form, and SOHC4, and cannot find something with this issue, and the solution. I have a home made timing light set up.

any ideas?

 

[Bert Jan]

If you can not get a full advance, it's most likely that your advancer is stuck. Check the advancer for corrosion or smuck. Could be your DIY is not up to par as well. Photo?

 

[teazer]

Bert is right on. The dyna rotor replaces teh OEM points cam and is designed to rotate slightly as the weights fling out with centifugal force. either the advancer is rusted, springs are broken/stretched or the Dyna rotor isn't sitting down properly on the two small "pegs" and is being bolted down hard in the wrong position. Please check and get back to us with what you see under the "points cover".

If you grab the rotor can you rotate it forward through about 15 degrees and does it spring back?

 

[johnnynogood]

hey,

those are not the issues, it is definitely me.

i have installed as per the instructions (i believe). rotor moves fine, no rust, no gunk, all perfectly clean. springs move freely, everything turns free.

i am looking for a video, photos, or diagram on setting the timing with a dyna S.

i will report back tomorrow once i get another crack at it.