Topic: Hanging idle and redline between shifts. Mixture/jet issue?

[Gorms]

I have read every thread I can find on the subject and there are lots.  I'm hoping my issue is a little different than most and someone can enlighten me.

First off the basics: 1977 cb550 with pods and Mac 4-1 exhaust.  Main jets upped from 90 to 105 and needle raised one notch.  Stock idle jets.  Idle mixture screws out 2.5 turns if I recall. 

For those who hate this setup and will only chime in to say I'm asking for problems... don't bother.  I have heard it and I am looking to make the bike run as well as possible with this setup.

I'll do my best to explain the issue.  The bike starts fine and after the normal choke will idle just fine.  Once moving, the idle will not drop from 3k-4k until I turn the idle adjuster way down and turn it back before it dies.  Also, on the shift from 1st to 2nd (and somewhat from 2nd to 3rd) the bike wants to REDLINE regardless of me shutting the throttle before clutching.  The shift from 3rd to 4th goes just fine.  Also, the throttle is like an on/off switch for the first little bit.  It is very hard to pull away slowly due to this as it is easy to either stall or rocket into the back of the car in front of me.  Fast take offs are fine (with the exception of the embarassing  and dangerous out of control rev between shifts).

Things to consider:
-Carb slides are closing fully when throttle is closed. I'm sure of this.
-Throttle cables are both free with no rubbing
-Carbs were vacuum balanced but not recently.  It didn't seem to help.
-Timing advance mechanism is clean and smooth and does not stick
-No leaks around carb boots or intake manifold

I am trying to understand the role of the different jets in the carbs as I ignorantly suspect that maybe the carbs are not transitioning to the idle circuit due to a mixture issue at either mid revs or at idle.  Would this explain why the throttle is like an on/off switch initially and why the revs wont come down while in neutral?  If I am lean at idle, will it want to stay at higher revs?  If so I am confused because after about 30 sec of choke, it likes it completely off and idles great leading me to believe im not lean at idle.  The bike pulls well at mid range too and doesnt gasp or stumble.

Please provide any thoughts you have.  I am at my wits end with this issue and returning to stock isnt an option at the moment.

Thanks.

[w1sa]

Why is the airscrew at 2 1/2 turns.?.........standard should be  about 1 1/2 turns.

Did you ensure the 'Fast Idle' adjustment and operation was correct (per the manual) ?

[lucky]

It needs a larger idle jet.

#42 mm idle jets.
Mixture screws 3/4 turns out?

Not sure where your needle is from stock position.
Stock is middle groove. Please count from the top.

I agree that with this year, the needle clip needs to be lowered ONE notch.

[lucky]

Where did he go?

[Gorms]

Thanks for the responses and sorry for the late reply.

There are too many of these threads where the OP maybe found the answer but didn't post it.  I found my answer so maybe this will help anyone with this issue who reads this.

Although I rebuilt my carbs completely when I built the bike and only had a couple hundred miles on it since, I pulled the carbs off and went through them because I didn't know what else to do.  To my suprise there was a fair amount of gummy deposits on the throats of carbs.  I cleaned them well with carb cleaner but my issues described above were likely due to the following:

Crazy reving between gear shifts:
Carb slides has some gummy deposits that were really sticky.  One or more slides would hang up.  When I shut the throttle quickly between shifts, I would use a good amount of force.  Since 3 of the 4 carbs slides and on levers with springs, I was able to shut the throttle all the way but one or more slides would not close quickly enough or at all because they are sping loaded.

Bad 1st gear starts/high idle:
I went through my build pictures and couldn't find one with the slow jets removed.  I was beginning to think I did not remove or clean them. I did so and saw that I could not see through them.  I soaked them in carb cleaner and blew them out with an air duster (smallest needle I could find was still too big).  The bike was indead having issues transitioning to the idle circuit because it was clogged.  I was likely trying to idle using the main jet and needle position which explains the inconsistent idle.

Also, I completely removed all idle mixture screws and found the there was an o-ring in one that had torn, curled up, and was blocking the hole.  This may have contributed some.

I took the bike to work today and it ran like a TOP!  Idled rock stead, revs dropped on command, and the initial throttle response was light, sooth, and progressive.  Problems solved.

[lucky]

A #10 steel guitar string is .010 and is stiff enough to use to poke through the idle jet to clear the junk out.

BTW.. The stock idle jet is a #38 mm.

The fact that your mixture screws are out 2.5 turns is a sign that the idle jet is too small  with pods, and I would bet  it hesitates when given quick throttle.

Sounds like you had good results fixing those other problems too.