Class and YICS

[Tkosanic]

I am new to these venture bikes. I used to be big into the xs bikes. Plain and simple. But these venture bikes caught my eye and decided to buy one. I keep hearing about CLASS and YICS. What is it exactly. I am trying to get the bike running tip top. So far I have taken it up the road and man does it ride way better then my xs did. Much more comfortable. I think it handles better too.

[bongobobny]

Hi and welcome!!

 

CLASS is Computer Leveling Air Suspension System only available on the Royale. It is a computerized controller module mounted on the dash that controlls an air pump mounted under the trunk that adds or removes air pressure to the front and rear shocks. It is wired so that it is operational only in the ACC position of the ignition switch.

 

I've forgotten exactly what the letters of YICS but what it does is to act as a vacuum storage box that tends to keep the vacuum balanced between the 4 carbs. It is a black box with 4 vacuum lines coming to it. They can develop leaks either from the lines or the box itself so many members have removed the system and capped off the lines. There is an excellent description of how it works in the service manual (which is available here in the read only tech section of the forums) but it is one of those things that works great in thoery but in reality doesn't really do that much...

[bongobobny]

Here's a link to the service manuals...

http://www.venturerider.org/forum/showthread.php?t=3384

[frankd]

YICS=Yamaha Induction Control System. It was only on the Mk I bikes (83-85), and when I bought my 83 brand new, I was amazed at the gas mileage. That's what the manual says YICS does, increase gas mileage at low engine speeds. Then the first time I took the bike apart, I couldn't see any way this would have much effect. Above and forward of the carbs, there was a box that consisted of 4 seperated air chambers. Between the carbs and the cylinder intake, there was a small (approx. 1/8") hose and it was connected to the YICS chamber. I guess it was supposed to give the intake chamber more volume (or length?) at low engine speeds. A lot of people have taken the YICS chamber off (and plugged the port on the intake tract) and said they saw no difference. On my 83, it's still in place and connected. Did it help the gas mileage?? Maybe. Several times I did get over 50MPG with the 83, but these were low speed (40-45MPH) tanks with little throttle opening. I don't ride like this very often. Another thing, some Mk I riders have had problems with the YICS chamber cracking and leaking. This causes that cylinder to run lean.