YICS keep or throw?

[garyS-NJ]

I'm chasing down a problem where my '84 backfires out the carbs as I rev it above 2500rpm.. I see in the timing inspection port that the timing isn't advancing (it jitters around) so I'm looking at electricals but I have had multiple problems in the past and this bike is a resurrection I bought cheap (seized motor).. So as I hunt, I'm going through it and with reports of YICS chambers splitting, I'm thinking I should ditch it (I'd like to ditch half the **** on this bike).

 

So does the YICS really make a difference? I'm doing fine without my appendix.

 

also, what about the crankcase breather that goes into the airbox. what a pain installing the box with this thing.. it was falling apart so I put a longer hose on it that is hitting the throttle linkage. I'm thinking put a small breather on there or a hose loop and plug the airbox/. thoughts?

[Great White]

YICS was shown to improve emissions and fuel mileage. There were some claims of more power, but I personally think that was a bit of smoke and mirrors.

 

YICS can be removed and capped, lots have done it. Some report better power and better MPG, but I'd take all that with a grain of salt.

 

My YICS is staying in place until I slide the VMax heads on my engine. Then the YICS has to go: VMax heads weren't designed for YICS.

 

Honestly, I'm not sold on YICS anyways. The telling moment for me was when the FJ1100 was released in 84. Yamaha dropped YICS on the FJ1100 because (according to Yamaha releases) the YICS scheme "showed no advantage on the FJ1100". What they didn't tell people was the FJ100 was virtually the same as the XS1100 heads where they defended YICS against all commers.....hmmm......

 

Crankcase vent is a different story. It was meant to evacuate the crankcase under vacuum. You probably will run fine without it, I just wouldn't.

 

Cheers

Edited July 18, 2015 by Great White

[garyS-NJ]

I know the crankcase has to breath. Just not into the airbox. My dumb question.

[Great White]

I know the crankcase has to breath. Just not into the airbox. My dumb question.

 

For sure.

 

The airbox scheme is to keep it under slight vacuum, which aids in relieving crankcase pressure.

 

As I mentioned, it would likely run just fine with a breather instead, I just personally wouldn't.

 

[Venturous Randy]

I posted this on another thread and for me, removing the YICS made the bike run better and I DID get better gas mileage. I have put about 150,000 miles on my 83 and am pretty familiar with it.

When you take your YICS off, throw the whole thing away. Then you will want to plug the ports coming out of the heads. The YICS system is the cause of a lot of problems on these bikes and even when working good, have no real value.

This is a good way to plug the ports.

http://www.venturerider.org/forum/showthread.php?86100-Plugging-YICS-ports&highlight=YICS

Randy

[garyS-NJ]

I took mine off yesterday and didn't detect a leak visually or by blowing or sucking on it. didn't bother to put a vac pump on it as the thing just looks too stupid to be of value. the tiny holes on the inlets couldn't allow for a whole lot of anything in my opinion and I'm thinking this was a flawed design attempt that quickly got dropped. bike looks better withyout it too (I ditched my side plastics that grill thing.). now for the black plastic heat shields above the heads. the front one is out and I need to re-install or pull the back one. do I need them?