YICS

[inanecathode]

Or YCIS? YSIC?...

What IS this device i keep hearing about anyway, other than a pretty trianglular box with hoses?

[h2olawyer]

YICS:

"The patented YICS (Yamaha Induction Control System), designed to improve combustion and increase fuel economy, is standard equipment, along with downdraft, automotive-style carburetors."

Copied from the Haynes manual.

Basically, it creates a swirl in the combustion chamber, using a charge of fuel / air mix.  The performance gain is minimal, but felt generally in the lower revs - mainly a "seat of the pants" feel.

The box is highly prone to leaks - both internal & external.  A leaking YICS causes a myriad of problems, most notably a hunting idle & enhanced stumbles.  The box is repairable and reckon is working on a better quality replacement.  I've had good results with the 2 I've repaired but it is kind of tricky to get everything sealed right.

The hoses can weaken with age & tend to collapse as the vacuum pulls the charge through.  They should be replaced with fuel injection hose.

H₂O