YICS Disassembly

[Walt_M.]

The purpose of the YICS is to make the intake flow more turbulent to better distribute the lean fuel mixture required by the EPA regs at the time. Supposed to make the bike run smoother, nothing about increased power. If you cap off the YICS and rejet the carbs, you won't need the YICS but you won't pass emissions testing if it is required in your area.

[Kid Jedi]

I agree that the yics has a greater effect on 4 bangers, but  think It plays a different role in our bikes, one that Jason may have overlooked. I think that at a certain engine harmonic the pulsing of the chamber actually helps force a fuel air charge in to the cylinder.


Properly mixed JB has some flex to it. if you are going to make your own yics I think you need a diaphragm in the center of a plastic inline fuel filter of the  proper volume.

The yics on a 4 banger is a completely different setup, with all of the intakes connected, and no plastic box, I think that kind of system would provide no bonus to our bikes.

EPA Conspiracy?!?! Oh My Gosh!

If the YICS system on our bikes was so amazing, then you would have seen it on more race bikes from the era, but you don't

The purpose of the YICS is to make the intake flow more turbulent to better distribute the lean fuel mixture required by the EPA regs at the time. Supposed to make the bike run smoother, nothing about increased power. If you cap off the YICS and rejet the carbs, you won't need the YICS but you won't pass emissions testing if it is required in your area.

.

I think the yics has a slight positive gain on the bike, but i agree with walt in that 90% of it was emissions considerations, but the real question is if that 10% is worth the possible vacc. leaks D:

[YellowJacket!]

From what I understand, it seems like the YICS is akin to an EGR valve on an automibile.

David

[Walt_M.]

Actual purpose is the same, different technique.

[Rick G]

Yamaha never promoted it as a emissions device , they indicated it was for improved performance. Either way it had no effect on mine , so now its history .

[Kid Jedi]

who in their right mind would promote an emission device on a motorcycle in 82?