What is it?

[venture83_98]

Finally got my carbs back together and decided to make sure nothing else needed attention before putting them back on. There is a black plastic box (air chamber assembly on the parts diagram) that sits on top of the motor. there are 4 lines going from it to each cylinder. 2 of my lines are cracked/ split. Do I need to replace the lines or can I remove them and cap off the ports in the cylinders? What does this thing do?

 

here is a pic:

[wrenchrob]

:confused24:

[Trader]

I think its a pollution control thing.

 

I've read some say remove it...others say keep it.

 

From what I've read....it's like it's personal chioice and doesn't make any real differnce.

 

Hopefully someone who knows what they are talking about will chime in!

[fixit3546]

Yep, it will....Search "Jason Mod" for another option, I ran that for a couple of years. cheap and simple.

[bkuhr]

It is the YICS system, supposed to improve mpg but most here do recommend removal.

The 4 chambers should be seperate from each other but likely leak to each other or air.

 

Plug the ports at the head with HEAVY DUTY plugs AND spring clamps. They have been known to be blown off.

 

quote from manuel:

 

YICS (Yamaha Induction Control System)

To increase fuel economy through more efficient combustion, the engine is equipped with the YICS, and the electronic governor type transistor ignition system with electronic boost control. In this configuration, the YICS consists of a chamber linked to the intake joint by a tube. Upon intake, the vacuum in the manifold creates a vacuum in the chamber; when the intake valve closes, the chamber draws in an air-fuel mixture. When the intake reopens, the mixture in the chamber shoots back out thru the angled tube and into the cylinder, mixing with and swirling the main intake charge. The swirling charge is then compressed and ignited, burn more completely and producing more power than that of a conventional engine.

Edited April 22, 2012 by bkuhr
info

[bongobobny]

Yup! That is known as the "bell" effect! It's one of those things that works in theory but has very little effect in reality. I kept mine but ran a bead of RTV aeround the seam to insure no leakage to atmosphere and replaced all of the lines. As stated you can cap them off and have for all intents and purposes no noticeable loss in power or fuel efficiency...

[Condor]

Remove it and cap off the bibs. It's the YICS added to California models in the early years to satisfy C.A.R.B. smog rules which were more stringent than the rest of the US. After 30 years the thing is leaking everywhere. Make sure you toss a carb sync at it afterwards... Your bike is probably a TDKC.

BTW you might want to replace the vacume advance hose between #2 and the boost sensor. By now it's probably leaking too...

[Venturous Randy]

Yes, remove and plug. I did mine years ago and wish I had done it earlier. I have had one of the plugs come apart and am thinking that when ever I have the carbs off again, I will use a short piece of hose with a plug on the inside the hose. I think this would actually be stronger than the rubber caps, even heavy duty ones.

RandyA

[venture83_98]

Thanks to all for the input. I thought I saw something about removing it a while ago, but couldnt find the info. Now I just have to find the right size caps. Have only found larger and smaller sizes. Going to try NAPA after work today. They should have them.

 

BTW you might want to replace the vacume advance hose between #2 and the boost sensor. By now it's probably leaking too...

Already done, along with the new tci unit...have the carbs back together, waiting on a throttle cable (should be here tomorrow). Still need to replace the fork seals and put it back together. Hopefully I am on the road soon.