Do carbs "have to" be synced after cleaning?

[slyone]

I really haven't examined the carbs yet and am getting close to cleaning, dip and new seals. Is it when they are seperated mechanically? and why can't the adjustment screw? be set to where it was?

[azr]

You can do a good mechanical synch and the bike will run, and maybe run ok. But to get it truly tuned you need to do a synch.

[loud et]

When you follow the carb rebuild tutorial, it will have you bench sync the carbs at the end....why? maybe they are not perfectly synced now. The sync is what makes the butterflies all open at the same time so all four carbs/cylinders are feeding fuel and firing at the same time. The main idle screw must be removed for disassembly, thats no big deal is just one screw. The air mix screws must be removed to clean the needle and replace the tiny o ring in there...therefore the new o ring will change the way the needle lets the air mix in so they must be re adjusted.
I did a bench sync only and my 1100e runs great. But...what I do not know is that it may even run better with a proper sync with a test meter. So what we think is perfect and what actually is , well thats why we follow the rebuild tutorial and do a proper aync with a test meter.

[Steve]

I really haven't examined the carbs yet and am getting close to cleaning, dip and new seals. Is it when they are seperated mechanically? and why can't the adjustment screw? be set to where it was?

Why did you move the adjustment screws? It's not necessary to move them when you separate the carbs or put them back together.
(Yes, there is more than one screw, there are THREE of them.)

And, who is to say that they were proper in the first place?

If you have adjusted your valves, you have changed the amount of air that the cylinder(s) can breathe, that will also affect the vacuum level.

Yes, you really do need to do a vacuum sync, unless you really don't care how your bike runs.

.

[tkent02]

Some folks don't mind bikes that run like crap.
Others like bikes that run perfectly.
Go figure.

[hjfisk]

A good sync makes the bikes run SMOOOOOOOOOOTH through all throttle ranges

[slyone]

just asking...lol! when I was a young teenager wayy back in the early 70's I worked for a guy who repaired all motorcycles but specialized in customization and Honda 750 engines/street/track racing. I was a young naive kid who did basics, oil changes etc and R&R the engines etc. I remember faintly he used to do alot of rejetting of course and vacuum syncing his bullet-proof engines..lol. He was the best and those were the days! Anyways, my brother and his friend have these small collections of bikes plus he just got some new Yamaha 1100 race bike and needed space so he traded me some stuff and I got this GS850 I wasn't looking to own since not biking in decades but my son loves it..LOL! So since I got it, I figured I'd go thru it so it's 100%..I also am gettin one of those first CB750's from 69' with just 7k on the clock so I'll be doing those carbs too..

[barnbiketom]

I also am gettin one of those first CB750's from 69'

I'll give you 500 bucks for it