To YICS or not to YICS?

[XJkid]

That is the question. I've read all the posts about how to disable it for synching purposes and where to get the elimination tool, but why would a person want to do it permanently? I understand it was for emissions and possibly fuel economy. Has it been deemed useless?

Guidance, please.

[fredintoon]

That is the question. I've read all the posts about how to disable it for synching purposes and where to get the elimination tool, but why would a person want to do it permanently? I understand it was for emissions and possibly fuel economy. Has it been deemed useless?

Guidance, please.

Hi Kid,
the YICS is an EPA mandated thing so we hold it in contempt on principle.
What it does in real terms is make it even more difficult to balance the carbs.

[DGXSER]

Simply stated, it is a small passage that joins the intake manifolds within the head for all four cylinders. As Fred stated, this makes synching the carbs nigh on impossible. So, the development of a YICS tool to allow you to isolate the cylinders and synch the carbs. Then of course, the creation of the YICS eliminator, so you can leave it in place permenently. Now your XJ will run and sych the same as my SH.

[madmax-im]

I 've had my YICS eliminator tool permanently installed for 2 yrs...wont ever take it out...YICS was a stupid idea to satisfy gov't emissions regulations...

[crazy steve]

I was thinking about asking the same question...

But didn't Yamaha also claim that YICS improved fuel economy? Do you take a hit on mileage if you block it off?

[madmax-im]

I was thinking about asking the same question...

But didn't Yamaha also claim that YICS improved fuel economy? Do you take a hit on mileage if you block it off?

Claims and reality...2 different things....actually dont think there was any change in fuel economy for me... Plus the benefits from blocking the YICS ports far outweigh any negatives...overall the Eliminator tool incresaes throttle response...making inputs more crisp...and the engine starts, idles and just purrs like a sewing machine...so it really does smooth it out...improvements were instanly recognizable upon staring the engine after installation and re-synching the carbs.

[JerseyJon]

Embarassing question

What's a YCIS? And what's a YCIS eliminator tool? I get that it's an emissions control device that we all want rid of. I also get that it connects the carbs and the head, probably to recirculate unburned fuel/air mixture or something.

From your description, this sounds like something I want. So what is it and where do I get it?

[madmax-im]

What's a YCIS? And what's a YCIS eliminator tool? I get that it's an emissions control device that we all want rid of. I also get that it connects the carbs and the head, probably to recirculate unburned fuel/air mixture or something.

From your description, this sounds like something I want. So what is it and where do I get it?

Yamaha Induction Carbueration System...basically each pair of carbs shared a port that would equalize the fuel mixture in those 2 carbs to burn fuel/air mixture more effiiciently especially if one of the carbs was out of synch. Basically for emissions standards and it did lower horsepower so perhaps there was some validity to improved fuel economy...YICS Eliminator tool is a long rod that goes thru all four carbs and blocks the ports off. YICS was only found on 1982 model XJ's of all displacements...A member here Yahman...or Larry makes a high quality YICS Eliminator tool I have one...get it...

[natemoen]

What's a YCIS? And what's a YCIS eliminator tool? I get that it's an emissions control device that we all want rid of. I also get that it connects the carbs and the head, probably to recirculate unburned fuel/air mixture or something.

From your description, this sounds like something I want. So what is it and where do I get it?

The YICS was only on the XJ's. So if you don't have an XJ you have nothing to eliminate. If you have an XJ then pm member yahman and he can hook you up.

[DGXSER]

YICS Eliminator tool is a long rod that goes thru all four carbs and blocks the ports off. YICS was only found on 1982 model XJ's of all displacements...A member here Yahman...or Larry makes a high quality YICS Eliminator tool I have one...get it...

Not an XJ owner...But...The ports are in the head not the carbs, correct? More directly the intake ports in the head. Just do not want someone looking for the place to put that tool in their carb bank.

[Cobia]

I have an XJ and a YICS eliminator, best thing I ever installed. It's imposible to synch your carbs without the YICS tool or the YICS eleiminator.
First of all, Don is right, the scavenging passgeway is in the head, not the carbs. It's a plenum, or passageway in the head, that joins all the intake manifolds in a common intake for all cylinders. The concept is that whatever fuel/air mixture produced by the carbs that is not consumed by the corresponding carb/cylinder combination will get sucked up by the next intake process of the following firing cylinder. Thus eliminating unspent fuel/air misture from escaping into the environment.
It's meant to scavange/utilize all fuel available before it escapes into the ether due to its residence in the intake manifolds.
Bottom line, it doesn't work and it makes the task of synchronizing the carbs next to impossible without the YICS tool. I fashioned a homemade YICS tool, thanks to veterans who selflessly provided some of the parts, to no avail. It didn't work. Maybe it was my ham fisted dexterity, but it wasn't until I installed the YICS eliminator that I was able to synch my carbs properly. My XJ has run flawlessly ever since.

[madmax-im]

Not an XJ owner...But...The ports are in the head not the carbs, correct? More directly the intake ports in the head. Just do not want someone looking for the place to put that tool in their carb bank.

Yeah I stand corrected its in the head...sorry thats what you get when working graveyard...

[trbig]

The YICS system on the XJ has a tube attached to the back side of the cylinders with 4 open ports.


















These 4 ports on the cylinder tube connect to 4 ports on the XJ head.








An XS head for comparison. Intakes are at top of the pic for the XJ, and facing bottom for the XS.









In those ports on the XJ head, up at the top, there is a hole that leads to an opening directly in front of the intake valve.









When the piston goes down on the intake stroke and draws in air/fuel mixture, it draws mainly from it's assigned carb, but also partially through those ports from that tube and from the other carbs as well. In theory, it should help richen up a slightly lean carb or vice-versa and let you go longer in between carb synchronizations. Without a YICS tool inserted into that tube along the back side of the cylinders, there's really no way to adjust your carbs since it's not drawing from just one carb. The YICS tool seals that tube in the spots between the carbs, allowing you to adjust each carb individually.

If you're the type that rarely works on the bike and do very little upkeep.. just jump on and ride, then a functioning YICS system is probably for you. For those that stay on top of things and want to know that each carb is functioning correctly on it's own, then closing off the YICS system would be better suited for you.




Every XJ head I've run, I semi-permanently tap and put in threaded allen inserts up into those ports in the head.









You can see one of them installed here with the black arrow pointing to it.









If you have no future plans to remove the head, then the YICS tool is a simple and fairly inexpensive way to bypass the system permanently, or just for testing and synching.

[crazy steve]

Those YICS ports might have a use if you wanted to run EFI or nitrous...

[XJkid]

Nitrous??

This thing is twice as much as I need as it is!! I wish to die having fun, but not that much. These engines have just the right ratio of hp to torque, that's why I love them. She (I haven't named her yet) runs great without a good sync, only a bench sync after rebuild. I have been doing a lot of maintenance work and cosmetic elbow grease, polishing case covers, resanding and recoating brushed aluminum parts, painting, etc...I can't wait to plug off the YICS, do the sync and experience what she can do!