Topic: Carb sync question

[gregripko]

Ok so I did a carb sync and my throttle screw is way too tight.... Is there a better method to carb sync that would give my throttle screw a little more play?

[goldarrow]

when that happens, I back out the idle screw and adjust each carb so the bike stays idle, then fine tune. Carbs synch tool still hooked up the whole time. 

[gregripko]

Good method.... Guess I'll have to resync.... Oh btw I noticed that when I tighten the carb screws down it throws the carb sync off (using carb sync tool that holds the screw while tightening the nut) is my goal to sync it perfect and tighten them down and however they end up fine or should I have them be perfectly syncd when the nuts are tightened down?

[goldarrow]

When the nut is tighten down, it will change the reading also.  It works the same way as adjusting the valve tappets.   Just have to play with them.   And I think this is the hard part if carbs synch.

[lucky]

Ok so I did a carb sync and my throttle screw is way too tight.... Is there a better method to carb sync that would give my throttle screw a little more play?

What do you mean "throttle screw"?

Depending on the year of the carbs it can mean different things.

[gregripko]

"Idle set screw"

[gregripko]

If I back out the idle set screw the engine will die though.... Does screwing all the carb adjustment screws down increase rpm....allowing the engine to remain idling while keeping the idle screw looser?

[goldarrow]

Yeah.  Adjust so that the bike idles. 

[gregripko]

Ok cool Ty

[gregripko]

The bike idles..... Is there a good average spot to have the idle set screw so it had decent play?

[goldarrow]

Idle screw is set when warm and forget, and it only takes very small adjustment to change the rpm when idle.  I guess set it to where it works for you???

[flybox1]

The bike idles..... Is there a good average spot to have the idle set screw so it had decent play?

yes, i reset the position when I do mybench sync.  Iturn it so it just touches the tab, and then in another two full turns.
this sets it at the beginning of its adjustment range, and allows the slides to still fully lower and close when turned out.

[gregripko]

Ok so my issue is that the spring is super tight when the screw touches the tab...

[flybox1]

is it the spring, or the gunked up threads of the idle set screw 

[gregripko]

Not sure.....by the time the spring touches tab the spring is super tight making it almost impossible to tighten....either the tab has to move forward or something else that i'm missing.....unfamiliar territory for me

[lucky]

I have a fear it is a mess.
Anyway....

When you sync the carbs the idle screw should be backed off all the way.
Make sure all throttle slides are closed.
Make sure when you start to open the throttle that all 4 slides start to open at the same time.
You can put your finger in the opening of the carb and actually feel when the slide starts to lift up.
Then start the engine and turn the idle screw just enough to keep the engine running.

Sync the idle on the carbs with vacuum gauges.

After you sync the carbs the idle can be a little high, so you can back off the
IDLE SCREWS a little.


Matter of fact when you are syncing the carbs if the idle does not want to go down keep checking the idle screw to make sure if is backed off enough.


This is what is going on.
There is a shaft connected to all of the carbs and when you pull the throttle cable,
it pulls open ALL of the carb slides.

And so when you adjust the IDLE SCREW it turns up the idle, BUT the idle on one of the carbs could be higher or lower than it needs to be because all of the carbs are connected to that same shaft.

So when you sync carbs what you are doing is getting all of the carbs connected on that shaft to all be open the same amount.

THEN you can control the idle with the IDLE SCREW. See what I mean?

[lucky]

Not sure.....by the time the spring touches tab the spring is super tight making it almost impossible to tighten....either the tab has to move forward or something else that i'm missing.....unfamiliar territory for me

Great photo.
That idle screw needs to be backed way off so that only about 1/4 inch is sticking out of the bracket.
But this is the important question.
When the idle screw is turned this far IN (excessive), the carb slides must be open when the throttle is supposed to be closed.

When the idle screw is backed off all the way all of the throttle slides should be CLOSED. Are they?.

[gregripko]

Another shot disassembled

[lucky]

Not sure.....by the time the spring touches tab the spring is super tight making it almost impossible to tighten....either the tab has to move forward or something else that i'm missing.....unfamiliar territory for me

BTW if you tried to tighten that idle screw anymore it would rip the threads out of the plate it is mounted on. Do NOT tighten it any more!

[gregripko]

I didn't

[gregripko]

I'll check on the slides

[TwoTired]

Not sure.....by the time the spring touches tab the spring is super tight making it almost impossible to tighten....either the tab has to move forward or something else that i'm missing.....unfamiliar territory for me

Classic error during vacuum sync is to adjust all four individual adjusters.  This skews the slide positions to where the idle knob can't do it's job.

The idle knob raises all slides at once.  The individual adjusters raise or lower each slide individually, driven from the same arm that the idle knob positions.
The mechanic is to chose which carb is master, (usually highest vacuum reading) and then adjust the other three carb t whatever the vacuum level the master has during adjustment.

If the carbs have been apart, part of the bench sync is to ensure the slide can reach the "floor" with the idle knob backed out, and using the individual slide adjusters.

The idle knob is now reaching the end of its adjustment range because ALL the individual adjusters have biased the actuator arm's position for proper idle.

[gregripko]

Can this be fixed through vacuum sync and without ripping apart carbs? Thanks two tired

[TwoTired]

Can this be fixed through vacuum sync and without ripping apart carbs? Thanks two tired

Yes, it can.  But, you have to be smart about it.  In essence you have to put one of the carb sync adjusters back to factory position and then adjust the others to it via vacuum readings.

[goldarrow]

Yes.  Idle knob at that position indicating very high rpm. You can adjust individual carb to bring up the rpm, then work your way down on the idle know and readjust each carb again. Keep repeating until you reach the level you feel is right on the knob