Topic: 1976 CB550 Carb Jet Needle question

[jrgphotography]

I rebuilt my carbs off my 76 CB550 that has headers (4 into 1) pipe with a glass pack welded on and air pods. I took out the 98 main jet and 38 slow jet and replaced it with a 100 main and 40 slow. I noticed that the jet needle with the 98/38 setup that the lock washer was placed on the 2nd groove of the jet needle. I assumed to place the lock washer on the 2nd groove on the 100/40 setup. I am running into an issue where the bike idles fine with the choke on as soon as I turn the choke off the bike idle increases high.

should I place the jet needle lock washer on the 4th goove instead of the 2nd groove? What does this do?
http://www.sohc4.net/index.php?q=content/cb500550-carb-id-and-specs

[TwoTired]

It's not a lock washer. It's an E clip.

The slide needle controls the mixture from 1/4 to 3/4 throttle position.  Raising the needle makes this range richer.

Have you looked closely at the stamping on the choke lever.  (Up is choke on, down is choke off)

[jrgphotography]

Your right it is a E clip.

So with the jet needled at the second groove from the top currently means ? if I drop it down 2 grooves (it being at the 4th groove) will this solve my issue?

Yeah the stamping on the choke lever is up towards the arrow is on and down choke is off. When I turn the choke down is when the idle picks up? I even tried adjusting the idle screw and its fully backed off

[TwoTired]

I don't know what position is best for the changes to stock that you've made.  Moving the clip from the 2nd groove to the 4th, will certainly make the midrange throttle positions richer.
Honda went to a lot of trouble to get those adjustments right with the stock components.  Since you changed all that, you have to repeat their experiments.

Learn to read your spark plugs and learn to do plug chops to get the jetting and adjustments correct for the mods you've made.  Or, take it to a dyno to get a fuel map.

Did you use the drill bit method to bench sync the carbs?  If so, I suspect you have all the slide adjusters skewed so that the slides can't can't close fully.
It's why I use the light method to bench sync the 550 carbs.

You have synced the carbs, right?

[jrgphotography]

will moving the jet needle clip from the 2nd groove the the 4th groove help with my idle problem with taking the choke off?

how do I perform a plug chop?

I'm not familiar with the drill bit method or light method whats that? I used the mercury filled sticks to sync the carbs I found brass fittings that screw into the intake manifold with a tapered nipple so that I can slide the rubber hose from the carb sync tool then adjust it that way.

[TwoTired]

will moving the jet needle clip from the 2nd groove the the 4th groove help with my idle problem with taking the choke off?

Probably not.

how do I perform a plug chop?

Reading past posts, and searching should answer that.  Its been cover many times before.
I guess I don't feel like typing all that out again right now.  Maybe in the morning...

I'm not familiar with the drill bit method or light method whats that? I used the mercury filled sticks to sync the carbs I found brass fittings that screw into the intake manifold with a tapered nipple so that I can slide the rubber hose from the carb sync tool then adjust it that way.

In the old style carbs it is possible to skew all the slide positions so that, although they are in sync, they no longer have enough travel to close off the air supply to the engine.  This makes the idle too high and beyond the control of the big idle knob.
Applying choke shuts off the air, allowing the idle to come down, releasing the choke restores the air supply and the engine races just like if you were to hold the throttle open.

The cure is to make sure at least one of the carbs is able to fully seat on the floor of its travel position.  Then use that carb as the master to vacuum sync all the other carbs to that one.  Then the idle knob can control the slide closing to the correct idle speed.

[jrgphotography]

When I look into the carb with the air pod off it looks like there is a gap of about 1/4 inch with throttle in off position. Should I adjust it so that there is no gap and use the idle knob to adjust it to the correct idle?

Also should I go ahead and move the jet needle E clip from the 2nd groove to the 4th groove?

[jrgphotography]

hey for the drill bit method to bench sync the carbs what size drill bit should I use as a guide? I heard 1/8 drill bit works?

[TwoTired]

When I look into the carb with the air pod off it looks like there is a gap of about 1/4 inch with throttle in off position. Should I adjust it so that there is no gap and use the idle knob to adjust it to the correct idle?

You do know that the slide bottoms are not flat and the air entrance side has an open angle, right?

Back out the idle knob so it is not a factor in slide positioning.

Pick a slide and adjust it's sync travel so that it closes fully.
Adjust the others so that they too close fully.
Pick a carb for a master, and vacuum sync all others to that one, without ever changing the master's sync adjustment.
Set the idle speed with the big idle knob.

Also should I go ahead and move the jet needle E clip from the 2nd groove to the 4th groove?

If you can't go by book values.  Then changing the clip position without indicating data is just a guess.
When experimenting, it is often easier to understand what effects what by doing only one change at a time.

[jrgphotography]

Yea I know that the slide isn't flat.
when adjusting them all fully closed how would I carb sync just one carb. Cause the carb sync tool I have has 4 hoses and I usually sync them so that there all equel. Also what number should I be syncing them too on thr carb sync tool I have thr motion pro one with mercury.   

[TwoTired]

Yea I know that the slide isn't flat.
when adjusting them all fully closed how would I carb sync just one carb. Cause the carb sync tool I have has 4 hoses and I usually sync them so that there all equel. Also what number should I be syncing them too on thr carb sync tool I have thr motion pro one with mercury.   

1- Back out the big idle knob so it is not a factor in slide positioning.
2- After ensuring that all the slides are able to fully close and rest at the limit of their downward travel through change of their individual travel adjustment. 
(On the bench, I use a small lamp on the far side of the carb bore and adjust the slide so that it >just< shuts off the light.)  Then do the same to #2, #3, and #4.)
3- Then use the idle knob to set idle position.

To vacuum sync:
1- Pick a carb to use as a master.  Say #1.
2- Use the sync tool to make #2 have the same vacuum reading as #1.
3- Then use the sync tool to make #3 have the same vacuum reading as #1.
4- Then use the sync tool to make #4 have the same vacuum reading as #1.
5- Now all 4 of the cylinders have the same vacuum reading and are vacuum synced.
(You can reset the idle knob for correct idle speed during any part of the vacuum sync procedure.  Whatever vacuum appears on #1 is the reference for any other carb to match.)

You do know that all the rest of the tune up check list must be done immediately prior to carb sync, right?  This includes cylinder valve adjust and ign timing.

Do use a fan to blow air over the engine to keep it from overheating the engine and the carbs.

[jrgphotography]

When syncing the master carb what should I adjust the carb to read on the sync tool it says in the Manuel to sync it to 16



Is there a write up how to do a cylinder valve adjust and ignition timing?

[TwoTired]

If the engine is running I don't care what the absolute vacuum reading is, as long as it can be equalized to the other 3.

The Honda shop manual has valve and ignition adjust procedures.  You don't have this manual yet?  You can download it from this site.

[jrgphotography]

Good to know thanks for the helpful advice

you wouldnt happen to know where in the site that manual is would you?

[TwoTired]

You could try the first item in SOHC4 forum...
Where is say:  download motorcycle manuals.
http://forums.sohc4.net/index.php?board=2.0

[Bill/BentON Racing]

TwoTired has got to be too tired from typing! You one nice guy to type all that.Bill

[jrgphotography]

TwoTired: Thanks again for all this thoughtful information. I just seen that your from Milpitas, CA I'm located in South San Jose, Ca. Do you work on bikes on the side?

my personal email is jrgphotography@yahoo.com go ahead and shoot me a email and I'll give you my cell if your interested on some side work. I just want to get my bike tuned, since i rebuilt the carbs at this point its all fine tuning.

So regarding the carbs:
alright so I backed out the big idle knob all the way.
adjusted the slides so that they shut off the light.
but the idle knob is too far away to do anything to the idle?


here is a picture to further explain

[fastbroshi]

   I believe that big screw is considered the throttle stop and there is a spec for that, as in how far to screw it in once it makes contact with that aluminum arm.  It's not very much at all, and I believe it's in the manual in the FAQ.  It's the one with the blue shadowed motorcyclde rim on the front, cb550.  Can't miss it.
 

[jrgphotography]

Its actually a idle screw turning it will push on the lever thus causing the throttle jets to move upwards allowing for more fuel.

[TwoTired]

So regarding the carbs:
alright so I backed out the big idle knob all the way.
adjusted the slides so that they shut off the light.
but the idle knob is too far away to do anything to the idle?

You'll have to screw the idle knob back in so it makes contact and opens the slides a bit for run operations.
I checked a couple spare carb banks in my stash.  There is normally a half inch gap that the adjuster bridges.

I'll send you an email so we can get this cleared up.  Far easier to explain all this stuff verbally.