Running sync: screw in or out, that is the question

I realize today that I didn't have a clue about which way to turn sync screws to have to right result while performing a running sync. In other words, if I want to give more vacuum to carb #3, do I have to screw in or out?

I thought i may not be the only one so I decide to share a few pictures with the forum.

To answer this, I put a carb rackI have on the shelf. Here is a general view:



Let's do it in the same order recommended in the manual, starting with carbs #1 and #2. If your vacuum gauges show that #1 sucks less than #2 , you should do this:



Second, we should balance carbs #3 and #4. If readings are lower for carb #4, you should do this:



Finally, to balance 1-2 pair with 3-4 pair, if 1-2 pair readings are lower , you should do this:



In other terms, first and second sync seem counter-intuitive, if you want more vacuum on the left , turn to the right. The third one is intuitive, if you want more vacuum on the right, turn to right.

I hope it could help.

 

You'll see right away if you turned the screw in the direction that you need to.
Nice job making it clear on which screws control which carbs.

 

actually you need to make #4 match #3. #3 is controlled by the idle screw

 

The way I understand it, the idle knob controls all butterflies opening at the same time.

 

yes it does move them all, but it sets #3 as the base point idle for the start of the sync. then the screw on far right sets 4 to match 3.
you can not match 3 to 4 by turning a screw or idle knob. the screw on 3 matches 1&2 set to 3&4 set.
turning screw 3 opens and closes 4.
great photos. I understand what you mean in the drawings, i think what is being said to your statment over the photos is
"Second, we should balance carbs #3 and #4. If readings are lower for carb #4, you should do this:"
you could have added if readings are high turn in opposite direction..
you did get the point across, and I would hope any one syncing could infer how to turn when reading is high.

 

Sync screws arent " In vs. Out ". They are " left vs. right " or " one vs.the other". Doesn't matter..... Turn the screw between 3&4. If the levels get closer, you're turn the needed direction.... If the levels get farther apart, turn the other direction.. Same procedure for 1&2, then Same procedure for left half and right half. It's very intuitive..... Really shouldn't take more than a few minutes.

Turn the screw a tiny bit, let go and blip the throttle. Let the idle settle, see where it is. Continue--- adjust, blip, watch, adjust, blip, watch, etc....

 

You're right, but I like to know what I'm doing before I begin something.

I used the terms "in" and "out" because every body who has already used a screwdriver would know what I mean.

 

Lol

 

I just performed my running sync. I was probably a bit stressed out because it seemed everything was exactly the opposite of what I wrote yesterday, Oh well !

Anyhow, I used my home-made sync tool:



There is none is the tubes on the picture but they were all a bit less than half filled with ATF. Each tube has a restrictor that you can't see on the picture (I should update that picture !). It worked pretty well, the liquid didn't creep to fast (I have at least 6 feet of tubing betwwen the top of the board and the carbs), so I had plenty of time to adjust. I did a bench sync a few months ago, so each pair wasn't actually badly out of sync, #1 was like #2 , and #3 was almost like #4, but left pair and right pair were not balanced at all (right pair sucked more vacuum).. I had to speed up idle with the knob at a point or the bile would have stalled when I tried to balance left and right. But in the end, I got them all equal.

I took the bike for a 40 km ride then. I had to slow down idle a bitit idled at 1200 after the ride.

I amaze with how the Seca900 handles like a small bike but performs like a big bike.

 

nice setup .are the right side and left side connected ?
will you do an assembly drawing with details?

 

now that you've done it, do you see that it takes longer to explain it than to do it ?

 

Yes they are connected at the bottom. I will put a few more pictures later this week. I'm pretty sure I made ie according to a plan and instructions I found on this forum 2-3 years ago, actually

 

Good job.

Gary H.

 

Well, lots of things are like that in life ! For fun, just try to explain how to throw a baseball, you'll be surprised...just kidding.

Actually the setup was a bit longer than the sync itself, because my tool is made of tubing a bit too big to fit the vacuum nipples on top of carbs, so I had to be inventive.

 

I can't find the plan I used to make my sync tool. Here is a pic of one of the restrictors:



It is simply a tube connector with a section of a small spray tube slipped in and epoxy-glued in it.

As for the drawing with details for the whole tool, I think I'll use some pictures and I'll write measurements on them.

 

I just threw in some MIG welder tips into the tubing.

Curious how my carbs look after the rebuild. Before, the ATF was all over the place. Hoping after the top end rebuild and the bench sync the carbs should be in a little better shape.

 

Anything that would restrict the flow of air should do the trick, the liquid will bounce a lot less, making the adjustments a lot easier. The bench sync is essential too.

 

I love the subject line.
For some reason it makes me think of the Karate Kid.
For what its worth... I use my electronic carbmate from either side or any side for the same results!
XJ FTW!

 

Here is the bottom part of the sync tool:



Damn** it, again I have a picture that doesn't want to cooperate...

All you need is four T connectors and to blind plugs. I used small t-wraps to secure the connections, and some tiny wire to hold the connectors and the tubes themselves to the plywood board.

I didn't measure them accurately , but I'd estimate that each tube is 7 feet long, the borad itself is 4 feet long.

I put the restrictors in the top section, but they could be locate anywhere I guess:



My tubes are a bit too big to fit the carb nipples perfectly so I had to insert short sections of smaller tubing, even then is wasn't a 100% tight fit when the tubing got hot.

 

I forgot to show clearly the idle knob location.

 

electronic sync tool do you have a link to where they are available?
found them
mfg site
http://tecmate.com/products/carbmate/

i see it aslo has a 2 to 4 carb adapter.
do you just use the 2 carb set up?

 

Thats the one I bought! But I bought it locally from a bike shop, so no on the link.
I only do the 2 carbs at time and it works a charm.
As long as you adjust the idle as you go if it goes above or below the 1050RPM it works really well.
A hell of a lot simpler than watching levels go up and down on a manometer, thats for sure.

 

How much did you pay for that cute gizmo?

 

I bought it in December of 2010 for $166.10 AUD. Wow time flies!
Been using it ever since and swear by it though.

 

Fiouu, not cheap, but if you enjoy it a lot, that's okay !

 

I made the 2 bottle sync tool first... it drove me nuts watching those levels moving the wrong way and then too far and then... ack!
I ended up with the carbmate after researching manometers and the like. I have a friend who bought a set of manometers for all 4... he comes to my place and we use the carbmate LOL.

 

Well , you would have had fun with my setup ! I was a bit anxious before I used it for the first time, but it went very very smooth, no hurry! And it is very forgiving if you turn the screw the wrong way, because the tubes are 7 foot long.

I know it would have been a different story without a good bench sync at first, though.

 

Looks like a gem but for 235 US bones...Ouch!

Gary H.

 

so with the carbmate the levels always go the right way and never too far......amazing!

 

I was said several times that if i'd turn the mixture screws a bit in or out to adjust the idle mixture after a running sync, it will affect the balance and I'd have to sync again.

Can someone explain that? I mean, is that possible that a little change in the opening of a so very tiny passage would change to total vacumm of a carb enough to be noticeable on the sync tool or guage?

ALso, I don't have a colortune, is pulling the spark plug and reading the electrode color the only way to tell the mixture is right or off?

 

And for half that amount, I got my carbtune Pro, can do all four cyls at the same time, use no fluids that could possibly contaminate anything, and balance the rack in only a few minutes.... I'll stick with my Morgan Carbtune

 

Québécois, if you change the mixture it COULD affect the balance. That doesn't mean it WILL.

I just recommend that if the rack was just redone, that the carb balancing is done, do a colortune, then carbtune again just in case anything did change substantially. Heck, why not colortune again, too. Do it as a " for fun" thing, not a "chore" thing.

After its dialed in, if you check it again next year at a carb clinic, do it once and youre done. It is just maintenance at that point.

If you don't have a colortune; use the plug color, or take temp readings of the exhaust pipes, or if you're really one with your bike you can go by sound/feel. Last, there are some smartphone programs that SUPPOSEDLY can listen and help you dial it in...I'm not convinced of that yet----

Dave

 

Dave, I clearly understand the difference between WILL and COULD, thanks for the explanation.

I used to adjust mixture by ear on my XS650 twin, i'm not so confident with the big four-in-line. But I may give it a try anyhow.

The engine idles pretty good and stable when warm, but not so good when cold, maybe it is not a question of mixture, maybe the enrichment circuit is not as clean as could be.

 

103$ to 127$ for carb mate unless you buy the adaptor for 70$
https://www.google.com/webhp?source...&ie=UTF-8#q=carbmate electronic carb balancer

 

Hi all,

I was able to sync all four carbs but I have a super hard time to get the idle range set. It seems to break down and then the engine stops. when turning the idle higher the engine screams like crazy and I just cant seem to find tve right position to keep it steady. any tips?

 

What have you done previously to the carburetors?

 

I took the whole thing out since it was very dirty and cleaned all parts and put it back together. did a bench sync too as described in one of the forum topics

 

So you just took it all apart, but didn’t replace anything? You can pretty well bet you have air leaks all over then.

How did you clean everything? What did you use?

 

Sorry of course I didnt just clean it I replaced all parts, bought a new kit for it. First I used a carburetor cleaning spray and then put everything into the ultrasonic cleaner.

 

Documented everything here https://andrewliyanage.com/yamaha-xj-750-seca-11m-vergaser-revidieren/?amp=1 sorry its in german but theres a google translate button if you on desktop

 

Ok. I will look through that and see if anything stands out. That will be a big help for me to examine for you.

 

wow thanks a lot for the help, I just made some videos which I will upload later may that helps too...

 

for years now I have always set the quad vacuum gauges on the carb boot nipples and see what carb 3 is running at, if its high, ill lower it or vise versa to an acceptable range. then I just set the others to match it, once they all match I adjust the idle knob. syncing is fairly quick once the tank is off. any bike with a 4 carb setup i've done it this way with stellar results every time. I will also note, once the sync is matching, the pilot air screws may need to be tweaked. just because your pulling equal vacuum does not mean your running leaner or richer on one carb vs the other.

Another note, at operating temp, you can use a infared thermometer to test the temp of each exhaust pipe right at the mounting flange for temp differences between cylinders, this is how we test and adjust final pilot air screws for ones running too rich and or lean. richer cylinders will run hotter from having more fuel in there to burn.

 

This is incorrect. Richer mixture will burn cooler.

 

My bad that is incorrect, yes I meant cooler. Thanks for setting me straight there Simmy!

 

I know you know your stuff, we all have brain farts.

 

I don’t see in the pics where you disassembled the throttle linkage to replace the throttle shaft seals.
-Did you do them?
-Did you make sure to put the air jets under the diaphragm back in the proper positions (bigger number toward the front of the bike)? It wouldn’t be the first time that these got mixed up.
-Did you make sure that the “36” air jets are all in the front of the rack?
-Did you make sure that you didn’t inadvertently swap any of the main jets with any of the idle jets?

 

Ok, So I thoroughly cleaned the carbs, back together and bench synced then put on the bike. I can get it to run by playing with the choke but if I just let it idle it will slowly die. Like I said, I did a bench sync on the carbs but have not done a running sync yet. Idle mixture screws are all 3 turns out. What do you guys recommend as the next step? I tried adjusting the idle setting (knob that adjust running idle) but she goes from slow die to increased RPMs. Should I back the idle air mixture down?? as always TIA

 

Idle speed screw only changes the speed.
The balance screw are between the carbs, on the linkages.

between 1-2 balances 1-2
Between 3-4 balances 3-4
Between 2-3 balances 1/2 with 3/4

 

Yup, I got relationship down from studying the earlier posts here...
So I should just work on the running sync first, then worry about idle air mix later?