What vacuum should I pull when testing the YICS?

[GigaWhiskey]

I sucked on it with my mouth and it seemed to hold and I am proud to say that I am not good doing that.

 

What amount of vacuum should I pull to test it fully?

[mbrood]

It's probably best to remember that Yamaha dropped that concept in 1986 without any mods to the bikes. Leaks can occur from cracks to the outside and also from chamber to chamber and then they can fail due to heat when the bike is running or open with vibration so an in depth test would be rather tough... I would opt to cap the ports on the engine... makes syncing the carbs a whole lot easier too.

 

A good leak test would need a controlled vacuum, a good gauge and time to see what's the "holding power" of each chamber.

[GigaWhiskey]

Yea, I have read that yammi stopped using the YICS in 86 but I have also read that it can cause some rough idling, loss of gas mileage and some of the kick when accelerating when not there on the MKI's.

 

I have read the Jason mod goes both ways on whether it is worth it or not.

 

Mike, i do appreciate your help. You have helped me multiple times over the years and you have been right on the money each time. So, is there any truth into the other things that I have read?

[Snaggletooth]

Hey Giga

 

The other Mike here........just a few of us out there.

 

I resealed the outer seams in the YICS box a coupe of years ago. Tried it for a while without any real change and then tested each chamber. Found two of them were leaking into each other so I did away with it and did the Jason mod.

 

I'd heard the comments on the "bumpy" idle but I haven't found it to be extreme at all. Hardly notice it really.

 

As far as MPG........can't say it hurt me at all. I'm pulling 42 on the highway miles without any problems at all. (under 70 MPH anyway). Power did seem to increase a bit but I had done so many other things to the bike I can't say it was all because of the Jason mod.

 

Da other Mike