Clarification on carb syncing?

I'm hoping to have a chance to finish dialing in my carbs soon and was looking over an article here on syncing with a single vacuum gauge, however I realized that I'm not quite clear on something. I thought 'syncing' the carbs meant getting all four butterflies to open and close at the same time, however it looks like the process with the vacuum gauge actually adjusts the pilot screws. Is that correct? And if so, can anyone point me to the process for getting the butterflies in sync? I would think I need to do that first before trying to adjust the pilot screws. Then again I thought adjusting the pilot screws was done by listening to the engine run and/or checking spark plug color so I'm not quite sure where the process with the vacuum gauge(s) comes in.

Assuming Mikuni carbs ? Syncing the carbs is to get each carb / cylinder drawing in fuel and air in a balanced way and amount resulting in a smooth running of the engine. Each carb / cylinder will create a different amount of vacuum depending on the condition of its component parts. To adjust the vacuum you use the adjuster on top of each carb slide. On no 3 carb, the one with the idle adjuser connect the guage to the vacuum port, start the engine and take a reading. If you only have one guage do the other 3 carbs in turn and adjust them to read the same as no 3's reading. Each time adjust the idle up / down to the same as it was on the initial reading for number 3. With only a single guauge you will need to do this several times for each carb including the initial number 3 as when each carb gets dialed in closer to where it needs to be it affects the balance of the others. This is why its easier with a 4 guage set up.
Once all 4 read the same then using a colourtune adjust the fual air mixture to get the correct combustion colour.

A quick guide to sync the carbs:
first sync #3 with #4, (#3 is the master, all other are the slaves)
then sync #1 with #2 ( independent with #3 and #4 values)
then sync the pairs (#1 + 2) with (#3 + 4)
do little 1/10 turns only, every little turn interact with the other carb vacuum.
repeat the steps until you get the minimum difference on all carbs.

Pilot screws are for fuel mix NOT vac balancing.
Get the pilot screws initially set all the same by the book so that the mix is somewhere close then balance the carbs and then go back to the fuel settings and jets for final tune up.
Vac balancing just gets all the cylinders doing the same work ( regardless of their individual condition ) and this is why setting all the slide heights the same does not mean they are balanced except maybe in a new/ rebuilt engine if you are lucky.
You will never get them truly balanced with just one gauge .
You really need a minimum of two.
When adjusting one slide it will alter the engine revs which will in turn change the vac reading of the cylinder you are trying to match to.
The reading you took of the first cylinder will no longer be the same once you start to adjust the second.
You will get your second cylinder reading the same as the first but they will still be off as a pair .
With two gauges you will see this happening and will be able to match the pair and so on.

Thanks for all the replies. So it sounds like I had it right about which screws are adjusting what, it was just that I got confused from reading the discussion and thought he was referring to the pilot screws. Scirocco's picture above shows what I originally thought was supposed to be adjusted when using the vacuum gauge, so I think I'm still on the right track.

@Warren3200gt -- yes, Mikuni carbs, I believe BS34? They are stock for a 1981 KZ1000K, with a recent rebuild.

FYI the article I am referencing can be found here: kzrider.com/forum/3-carburetor/593426-ca...-single-vacuum-gauge
In this a technique is described similar to what Scirocco mentioned. Just judging by the heat of the four pipes shortly after start-up, I believe each pair of carbs are synced fairly close to each other, however there is quite a noticeable difference between the left and right pairs, with the left side running cooler. I also noticing some 'chuffing' from the left pipe and I'm still having issues with smooth running until the engine is fully heated. Something is obviously not quite right yet and I'm hoping getting the carbs balanced will take care of most of that. Then I can get back to fine-tuning the pilots (which I assume will be thrown off again when I do the balancing).

Pipe temps can vary widely (by 100 deg or more) even when the carbs are synced to a smooth idle. Not sure why, but it ends up that way often. Maybe a slightly tighter exhaust valve clearance allows burning gases to get into the exhaust just a bit sooner and that increases temps. There could be many reasons for it. Maybe it could just be the way the wind is blowing that day.

Well I can rule out the wind -- there was none. I've actually been checking the temps for the past month or so and it's always the same, and even after a short ride there is still a noticeable difference in the radiated heat from each side. I'm guessing the adjustable valves were common on the bikes from the 70's, but there was no adjustment on mine, things just bolt on and get torqued down and that was it. I'm assuming in '81 they converted to hydraulic lifters similar to what my old car had?

Looks like rain all day on Saturday. Sunday will be clear but only in the 60's, so I might be able to get the engine warmed up and try to get the carbs synced then.

Manual valve adjustment is still common on motorcycles. Hydraulic lifters are quite rare.
The valve lash must be checked on your KZ, and any out of spec need a shim change.

If a carb sync seems to be very difficult to adjust or the values on the vacuum gauge change every time you pull the throttle could be a sign of a vacuum leak at the intake boots, a leaking valve or bad compression by piston rings.
A misfire during a carb sync or a fully open damper valve,(shattering pointer), can easily destroy your vacuum gauge mechanic.
One special note before you do a carb sync is to do a sync test on your vacuum gauge to verify all clocks showing the same value on one vacuum port.



Michael

If you don't have one already, you should probably get a factory service manual. It will describe how to adjust the valves.

Since the valves have not been adjusted, you may want to do a compression test to see where the motor condition stands. Without that, you might be wasting time trying to sync the carbs.

Make sure to get a compression tester with a check valve in the very tip that gets inserted into the motor. Without the check valve there, the reading will be low.

and the valves should have proper lash before trying to adjust the carbs.