Ok, I built my carbs and synched my carbs and color tuned each cylinder!
IT RUNS GREAT!!!! Talk about smooth....
So why would I have wanted to use a YICS tool?
I didn't and it worked out excellent/!?
If someone could tell me, I guess I just don't understand it's purpose.

Search. This has been debated a few different times. If you're happy, don't get one. I've got one on order, but right now things are running pretty good. I'm curious to see if they get even better. . . .

Why should you use the YICS? I'm going to say because the manufacturer of the machine specified it's use for optimum performance. Not to mention that common sense tells you that you need to isolate each carb circuit from one another to be able to tweak it correctly. I'm sure you could get away with it as it is with little concern for problems but if your running good now, just imagine what might well be the outcome (in fact I'm certain you'll find an improvement) should you use the tool. You've nothing to loose and a happier bike to gain if you do. I've read the other posts on this and a few fellows insist that there was no change between the using the YICS and not using it on their bikes. I would suspect that the reason there was no change between the two was that the passage was plugged up with deposits. Now I'm not saying that their experience is impossible nor improbable but I think (parish the thought) that the majority of our machines will need the correct tune up to run right. Gotta optimize the existing systems before you fuss with it in order to realize the potential each step can provide. Hope this helps.

Robert wrote:

I've read the other posts on this and a few fellows insist that there was no change between the using the YICS and not using it on their bikes. I would suspect that the reason there was no change between the two was that the passage was plugged up with deposits. Now I'm not ...

Someone with alot of experience and good ear could get the sync acceptably close without a YICS tool. For many folks that is fine. They never need the performance or the balance.

Personally if you are an occasional in town rider don't sweat it. If you ride on the highway at sustained speeds it is worth the trouble.

Wait until you drop a valve from a lean condition at hgihway speed

Don't ask me how I know this.

Quote::

Someone with alot of experience and good ear could get the sync acceptably close without a YICS tool. For many folks that is fine. They never need the performance or the balance. Personally if you are an occasional in town rider don't sweat it. If you ride on the highway at sustained speeds it is worth the trouble. Wait until you drop a valve from a lean condition at hgihway speed Don't ask me how I know this.

Having tuned bikes at 2 carb clinics now, I have to say that yes they can be tuned close without the YICS. It would be luck and luck alone to get it right. I had one guy show up at last years with a 750 he had tuned by ear. It sounded good, so I thought I wouldn't have to do much. When I checked it with the colotune I found that 2 cylinders were hitting intermittently due to a lean mixture. I then found the sync to be way off. Now this gives more credit to the colortune than the YICS however if he had missed the intermittent idle by ear then the ear cannot be trusted completely. This is due to the ability of the other carbs to compensate. So how able are they to compensate for the absence of the YICS? I may do some testing next clinic and set some without the YICS and have another skilled tuner check my findings. Then insert the YICS and see what we find. We'll see what goes.
I am still of the opinion that the YICS is the best and surest way to be confident in your tuning. Without it, there is doubt. Not to mention that having owned and used Mike's YICS tool to tune countless XJ's makes me certain of it's quality, durablity and reliability. You will never see me at a carb clinic without it.

Blue Maxim, I'll be interested to hear what the results of that test will be like. I do ride on the hiway at higher speeds and if the tool can indeed make my bike run better than it already does,.... then I need one too.
I guess I dont understand the purpose of the tool and how the YICS portion of the engine operate to fully appreciate this tool.
Anyone want to take time to enlighten me? I'm NOT trying to be smart, I've been a mechanic for many more years than many riders have been riders. But I've never studied or read about the YICS portion of this engine, I simply tuned it like I'd do any other multi-carbd engine, changed plugs, set carbs to base settings then synched carbs, color tune adjusted the mixtures then resynched carbs. sounds great!!!
BUT if it can run better.... I'd try it!

Ok, this is from my basic understanding and I'm only writing it out so I can be corrected. If you need more details, wait for the pros.

The YICS is just a system of air passages connecting all four of the intake manifolds. The primary purpose as I understand it is to create turbulent airflow to give a better fuel-air mix at low engine speeds (I presume at higher speeds, the charge is coming in fast enough to get well-mixed when it slams into the cylinder). The YICS tool blocks those conencting passages, so Carb 1 is ONLY feeding Clylinder 1, etc. That way, the changes you make to the butterfly position or mixture screw only directly effect the combustion in that specific cylinder (well, not ONLY that one in the case of balancing since balance adjustments are between pairs, but you know what I mean, I think).

My thinking was that since it RUNS w/out the passages blocked, you'd want to adjust it as it will be running. But blocking the YICS allows direct relation of a change in one carb to the effect in one cylinder.

How's that?

SOUNDS PLAUSABLE TO ME. lets see what else comes in
Thanks

YICS

Isn't that what I said? LOL

Great pic.

BTW, just to clarify what I said. I didn't mean to imply that the YICS was only open/on/operational during engine idle and is somehow disabled at high revs. It's full-time. Low idle is just when it has the greatest impact on performance. Again - as far as I understand.

It never occurred to me that this engine fires cylinders individually, I thought they fired in pairs.

That is a great illustration of the process. What it shows is how the YICS port allows a cylinder to suck fuel/air mixture from the other carbs. Giving it enough fuel to fire if slightly lean or maybe run rich if the other cylinder is rich and leaves extra fuel/air mixture in the port. Without the YICS you could therefore tune 2 cylinders in harmony but not individually and therefore not acheive optimum results. But it is true that the YICS port is for harmony! So yes you can tune the bike well without the YICS tool but not optimually. Has more impact on racing or speed trials maybe than anything else.
You can also see how a high float level could make another carb rich. The higher the fuel is to the air flow the easier it is for the cylinder to suck it out. So you would colortune that cylinder lean to compensate. Then if later the fuel level was reset that cylinder would run lean and endanger a valve.