Topic: 74 cb550 Not idling after bench sync

[bryanbrady07]

I feel as if my efforts this past week to conduct proper tuning have lead me nowhere, so I figured I could consult with the more experienced for some guidance.  The videos shows the bike running at proper idle speed and after a carb clean and rejet. I did not mess with the air/fuel screws or slide adjusters prior to this.   

Some background info: Running velocity stacks with screen filter and 4 into 1 exh. 022A carbs
115 main 40 slow needle 3rd from top which is middle notch(stock is 100 main 38 slow) 

Shortly after this I took the bike out and got it through all 5 gears and plug check showed to be running a bit rich.  So i figured it was possible that that since I had it idling for a while, it could just be a bit rich at idle. (Apparently it is common for this model to idle a bit rich) Anyhow, I took carbs off and proceeded to sync the slides lower and did a bench sync with the light method as recommended by TT. I wanted to bench sync it before of course vacuum syncing but I believe this is where I went wrong.  After I put carbs back on, I could no longer get it to idle without about 1/8 throttle and of course the idle adjuster was turned all the way in because I lowered the slides.  It was also blowing out a bit of white smoke.

Did I lower the adjuster slides too low and if so what is a good recommended height? Should I try going back down to stock pilot size and see if I can get idle (Even though videos are idling with 40 slow in)? 

Could white smoke be a starving carb even though I made sure to adjust floats to 22m stock? Or possibly a small vacuum leak?

Any input or thoughts would be greatly appreciated
Thanks
-Bryan

[bender01]

Why not adjust the air screws if its rich. The light test Im not familiar with. I use a wd-40 straw as a thickness guage for slide height on a bench sync. Adjust idle screw accordingly.

[bryanbrady07]

I was adjusting the air screws but could not get an idle rpm because the bike would die with anything less than about 1/8 throttle.  I think I set the slides too low but I did notice a slight rpm increase at about 2 1/2 turns out. 

[BomberMann650]

You're right about the rich at idle thing.  The 069A/022A carbs are basic as carbs come.  (Leading some to think the PD carbs superior)

Good news is, you oughta be able to take the vstacks off and check your slide positions.  To comfirm you arent snuffing the bike out.

The big idle screw is your friend, and there is no crime in fiddling with it.  It's only job is to open the slides anyway.

Did I read that your big idle screw is turned 100% in?  Then you need to redo your bench sync.  Use a 1/8" drill bit this time.

[bryanbrady07]

Just to clarify. I performed the light method (moved adjuster slides down until no light shows through from other side) from the front side of the carbs (side shown in pic below.) This is the side that I need to redo and perform with an 1/8 drillbit?

http://i.imgur.com/7y2HVxj.jpg

[harisuluv]

If you want to increase the idle rpm, that is done with the idle set screw (singular) not the air screws (4).  If you are adjusting the air screws to alter the rpm, you're doing it wrong in this case.

[bryanbrady07]

I am aware of the function of the single idle screw.  Where I believe I went wrong is I adjusted the throttle slides to sit completely shut from the front or the side that connects to the boots. Then when I went to adjust idle screw I could no longer turn it to raise the slides which I believe is why it can no longer idle.   

[harisuluv]

Yeah that sounds like it could be the case, here is something i wrote up awhile ago about bench syncing. 


There is no "master" carb on those style carbs.  On PD style carbs (77-78) #2 is the master.  On your set, the "master" can be any carb you want it to be.

Now, if you are synced well and have range of adjustment from the correct position in relation to the idle set screw, then it's not that big a deal what you're showing.  If you look at the lifter arms they are often bent down or up which is basically what can cause the variation.  They get bent in, out, side to side, sometimes they touch each other in the middle and bind a little bit.  They are not an exact part, but they don't have to be, because it's adjusted with the individual adjusters.

Really the fool proof way (almost) to do this is:  We'll use a 1/8" drill bit for the example tool from airbox side.  Get all the slides off "the deck" that way nothing will bind and throw everything else off.  Designate #2 the master.  Back off the idle screw so it's not making contact.  Now get the nut on #2 to where it has about the normal amount of threads showing like you want on your picture on the right (3-4 threads, 4 is good).  Now here's where the foolproof part comes in:  You have only set where you know the threads at the top are a perfectly acceptable honda factory level which allow for range of adjustment via the idle screw.  None of the other slides are BELOW the level of #2 (which would mess this up).  Now, adjust #2 with the IDLE SET SCREW with your drill bit (just close).  Verify range of motion IN and OUT with the idle adjust screw (should be making contact with the stop when turning in and out for providing a reasonable range of adjustment).  Next, fine adjust #2 with your drill bit (or whatever).  Now you are going to have for sure the sync set IN RELATION to the idle screw.  In other words, you're not going to get them all synced to each other only to find when you adjust the idle screw it's not even touching and you have no adjustment!  Now all you have to do is set the rest to the same level as #2 (adjust each with the individual adjuster, you don't need to really mess with the main idle adjust now).  Easy!