To use or not - YICS Tool

Well I'm sticking my neck out. I've been naughty and did the sync without using the YICS tool. It works perfectly - Spark Plugs looks exactly the same and with a good color, idle is very smooth and it pull like h...
I've just been lucky or?
(of cause the carbs are clean, the valves are done, float hight checked and with a new air filter)

 

OK, worms you want, worms you got.

Here's the situation; hang on for the arguments.

You may have gotten lucky; OR you were close already; OR it's not as sync'ed as you think (and could even be better.)

Here's why: YICS tends to act as a "damper" or "equalizer" in the intake tract. Anytime you're measuring/adjusting one cylinder, if the YICS is still open then that cylinder is receiving secondary intake vacuum "signals" from the other three cylinders. This secondary intake can act to "mask" a slight out of sync condition. So what you get is this: Sync'ed with YICS open, you could still be slightly out of sync, and can't tell. Sync with YICS blocked, and you'll still be sync'ed with it unblocked.

 

i'am not saying anything

 

Listen to Fitz. You can't balance vacuum properly when they are sharing vacuum. The japanese guy who designed this engine knew this and put a place in the engine to put a tool so you could sync. That is why that gallery port is the way it is.

 

Close enough is good enough sometimes. This aint rocket surgery. : )

 

Rocket surgery LOL we say that at work all the time!!!!

 

"Close enough is good enough" does only one thing, my friend--

It shortens the amount of time/miles before you need to REVISIT and DO IT AGAIN.

Don't get me wrong; I love working on old bikes or I wouldn't be here; I DON'T however, want to keep doing the same thing over and over.

I prefer "set it and forget it" (for 5000 miles anyway.) Lots more time to actually ride and enjoy my XJs.

 

Yeah?
If its idling and running good he cant be that far off sync.
It might be dead on.

 

It maybe good enough to ride. But it isn't right.

Unless he's got the one engine where all 4 jugs are pulling exactly equal vacuum there's a difference. The YICS removes the difference unless it's blocked off.

 

Which came first, the chicken or the egg? And, should you hire the fox to guard the henhouse, just because he offers to work for a lesser wage?:

D. Verhey sez:

 

See? Worms, I said. Big can, open again. But it shouldn't be.

Yamaha built the bike.

Yamaha made the tool and said "use it."

Yamaha HAD a reason for that.

That is all I need to know that I need to use the tool, period.

Yes, we can argue all day about how close you may or may not get it, and all of that is very true. However, the pure science behind it says you will get more accurate results with the cylinders isolated. And that much IS true, based on my own, real-world experience and a comparison done with a Morgan Carbtune with and without blocking YICS.

YICS does "dampen" out an imbalance, especially at idle, as above. Block it and you remove the dampening/compensating effect. Pure and simple. HOW MUCH effect YICS was having we can debate until there is no more horse left to beat and the can is empty, but if you block it you eliminate it from the discussion.

But then again, what do I know. I put another 120+ miles on my XJ today, and it started/ran/idled flawlessly, even in stop-and-go rush hour DEEtroit traffic. Just like it has for the last 3600+ miles since I got DONE with it.

 

Hey, pirok, if your yics ports are blocked, that is your built in YICS tool.

 

the "hole" your blocking off on a 750 is about 3/32 inch or 2.38 mm, minus any crud that may be in there

 

I am with Fitz on this one for sure....
I know how my bike ran when the sync was close and I know how it runs when it is perfect! Night and day difference!
The tool isn't expensive and once you have done it a few times it is easy.
Be nice to your bike and get the YICS tool and do it right. You'll be glad you did.

 

Did you sync your carbs after you got the carbs back from being cleaned?

 

I used to think you needed the tool, but after thinking about it and reading the procedure I now disagree. I don't recommend against the tool, but I think with the right tools the purpose of the YICS blocking tool becomes moot.

Heres what I (currently) believe:

The Yamaha engineers were not wrong...but they wrote a procedure using a single vacuum gauge. If you tried to sync without the YICS blocked with a single vacuum gauge, every change you made would affect the other cylinders, and you would be syncing for a really long time...enough to heat up the engine too much, and enough to make you start looking for a better solution. The solution is easy, just block off the ports and you will no longer have to worry about the effect of changes on the other cylinders.

A Carbtune, though quite useful, has a resolution available limited only to the resolution of an individual barometer The smallest increment on the carbtune is 5 mm Hg which is equivalent to 2.68 inches H2O. You can get a resolution with a manometer of 1 mm H2O, or .04 inches, or 67 times the resolution!

However, if you built a contraption like the one I made, that allows you to use valves to switch between cylinders very quickly so that you can dial in the sync in a way that you can't with a single vacuum gauge or a Carbtune . A manometer is the most accurate vacuum COMPARISON device you can get.

So in conclusion, I believe Yamaha advises the use of YICS port blanking due to the tools available, not the inherent nature of the YICS. I also think that a bench sync followed by a manometer that has vacuum lines that can be quickly switched to different cylinders can provide sufficient resolution to account for the dampening effects of the YICS, no matter how big or small they are. Ultimately, I believe that a sync in normal "running" conditions will account for any discrepancies with the YICS, which cannot be accounted for if the YICS is blanked off. Especially the manner in which the fuel burns, the forces exerted on the piston, and the heat and velocity of the exhaust. Let's be honest, blanking off the YICS alters the way the engine runs in a significant way.

Of course, it's probably just easier to throw an oiled rag in there an be done with it. Easier, however, has never been my nature.

 

I remember someone did a write up they synced the carbs with the yics open. Then they blocked the yics and found up to a 5mm difference so they adjusted it with the tool in place. Then they took the tool out and checked the sync and it was still right on.

So I vote block the yics passage.

 

Bill, You are hard to figure out sometimes.
This was a silly question.... Of coarse I did.
I did a Sync then a colortune and then another sync and another colortune. This way I knew everything was set up perfectly and my bike runs better than anything I have ever ridden. And I have ridden a lot of bikes over the years.

 

Well, that's a very interesting idea, and a good point.

The early Euro XJ550 (1980 yics) service manual does indeed show a single, "switchable" vac gauge in the maintenance section when discussing the synch procedures; however, all of the US service manuals (for 550, 650, 700, 750, and 900 models) show what is obviously a carbtune-type, 4-column device.

 

I guess that reduces my point to only the available resolution of the device, and nothing to do with the problem of moving the gauge between cylinders.

What was most commonly used in 1980 - 1986, though? Is it possible that the engineers wrote a procedure for a device that is different than that shown in the manual?

I've already changed my mind twice! Give me all your money or I'll do it again!