Yamaha YICS engine mod?

[mojo mofo]

I was reading an article on SVRider.com that mentioned an old school Yamaha YICS mod that the author says greatly smoothed out power delivery. Here's the snippet of that section of the article:

http://www.svrider.com/articles/oct04/modTrain.htm

So then I go for SMOOTH power delivery, since I do love silken smooth torque delivery. I do an old trick on the intakes that never fails...taking a tip from the best engine builder and innovator in the world...Yamaha. Maybe you old farts like me remember the Yamaha YICS system" It stands for Yamaha Induction Control System...basically a loaded intake plenum....already charged with newly atomized fuel molecules...just waiting to be called upon to be sucked into the combustion chamber and banged off....good idea I sez to meself I'll just pirate this idea and see what cooks out...literally. Cheapskate me goes to the auto parts store and buys about three feet of intake/fuel line, and one brass T....I cut equal lengths of the line and hookemup to the intake manifolds, then Tee off to the petcock.....makes vacuum synching a snap....hook up the old mercury sticks...dial it in....hookerup......MY O MY!!!!

It's so smooth with this YICS system now I can turn down the idle to 800 SMOOTH rpm and the little fella can compete with the bigboy Harleys in the coolguy idle rumble acoustical music category!!

Anyone familiar with what he is talking about? What do you guys think about this mod?

[D.T.]

I just sold my Yamaha XZ550RJ Vision when I bought my SV. The Yamaha had the YICS chamber on it. I removed it because it leaked between the two chambers and caused idling problems. I also didn' t notice any performance gains when I "repaired" it. I had the head milled and the valve seats redone, but I think it be most effective if you did a leak down test and got the valves to seal perfectly.

It's just a hose connected above an intake valve to a small chamber, about 20cc's or so to each cyclinder.

Here is one pic of the Vision engine. The YICS chamber is between the downdraft carbs.

http://www.ghetti.net/rov/Engine_View/engine_rd.gif

Here is what my old manual says:

To increase fuel economy through more efficient combustion, the engine is equipped with the patented Yamaha Induction Control System. In this configuration, the YICS consists of a chamber linked to the intake manifold by a tube. Upon intake, the vacuum in the manifold creates a vacuum in the chamber; when the intake valve closes, the chamber draws in some air-fuel mixture. When the intake valve reopens, the mixture in the chamber shoots back out through the angled tube and into the cylinder, mixing with and swirling the main intake charge. The swirling charge is them compressed and ignited, burning more completely and producing more power than that of a conventional engine.

[Ikazuchi]

There's a mod like this for the R6. Most people seemed to be happy with it... I never had the chance to try it.... or the time....or energy....