YICS & flapper

[Kid Jedi]

so there is this yics thingy. i have talked to a few people about it, and the best i have been able to figure out is that you need it unless you re-tune the carbs to run with out it. i plan on putting mine on the dyno, tuned with and tuned with out. to gat a real comparison, i notice that with yics, I cannot get her to power wheelie, in that i have to rev her and drop the clutch and with the YICS she stand up if I just shift a little to late.


However, the YICS is a BITCH to get right. i cut mine in half with a surgical saw and glue her back together with jb weld to permanently fix it, jb is fuel proof after all. the whole inside chamber is coated with the stuff and I replaced the lines to it with metric fuel line for a vw bug.

Also the flapper door is crap. its and emission thing, BUT if you pull yours off, get the bike tuned on a dyno, because you will have less ponies till you do.

[inanecathode]

The yics does almost nothing for developing power. I dont know who you're talking to but they dont know what they're talking about, you dont have to retune the carbs when you take off the box. Power wheelieing and adjusting your riding style to how you think/want the bike to perform is not an objective test.

The JB weld wont hold either, unless you get a virgin box the plastic will be permeated with fuel and the jb weld wont stick very long. Something else to think about the yics box isnt rigid, it's plastic and it flexes minutely every time the intake valve opens. How many times does the intake valve open in one ride? Thats how many times you're flexing the joint you've made.

The flapper door is not crap, it was designed by yamaha to fix an off idle stumble every single vision going out the door had. Thats why it's called 'the vision stumble'. It's not an emission thing, it has absolutely nothing to do with maximum power output (via dyno testing) and it has nothing to do with power output period. Its purely a vacuum modulated device to help maintain venturi velocity under a sudden throttle opening. Under maximum throttle there is atmospheric pressure behind the diaphragm and the spring pushes the flapper wide open, have you even looked at the vacuum flapper before coming up with an opinion? Even with accelerator pumps the relatively gigantic mikunis on these things have such a large venturi as soon as you open the throttle the air quits moving. Air moving in a venturi = vacuum vacuum = fuel delivery. Air not moving = no vacuum. No vacuum = no fuel delivery.

Look i really dig your enthusiasm, and its something alot of people lack, but these bikes have been around longer than I (or you) have been alive. Theres been an absurd amount of brain power and research that has already been dumped into them. I'm not saying don't experiment or do all sorts of cool stuff with the engines and what not, but dont come on with absolute statements about stuff thats proveably wrong. It just doesnt help your credibility.

[arthurdent510]

You don't need the yics, I think most of the guys on here run without it.  Only affect it has that I've heard of it it makes you idle a little higher.  Just cap the ports and tune it like that, no problem.

Flapper is not just emissions.  The flapper helps to take care of the stumble that our engines have.  My engine went from being very finicky and prone to stalling without it to a very reliable and strong motor with it.  Leave it in, there's a reason they added it...

[Rick G]

 What they said!
The new HD XR1200 street tracker , has a flapper box. Even with fuel injection, the 50 mm throttle body will suffer from low air velocity . Theirs is controlled by the ECM not vacuum like ours

You are making statements that we , here on this forum, have resolved years ago . Many have piped up and said they are going to toss the Air box . But, BELIEVE ME , when I say, you can't get a Vision to run properly, with out the air box and flapper door. A dyno won't show this very well , its a low end -mid range device, governing throttle response , not maximum power.

[don_vanecek]

Way back in the mid 1980's one of our-most likely long gone-original paper ROV members (ROV was quarterly newsletter in the oooold days) named Andrew Biehle, wanted to put individual air filters on his Vision. He did know about the fix-and his bike may have had it, unlike myself, who did not even know about the Yamaha flapper fix (and a curse on my dealer who SHOULD have known about and should have installed it prior to my purchasing the bike in 1984).

Anyway he did like a ten page report on what he did to his bike and just as previously mentioned, no vacuum is a big problem. To quote his report, "The main problem with the carbs is the top opening is alot larger then the inside barrel that goes to the intakes so when the top opening is made smaller, closer to the size of the inside of the carbs, this give you better vacuum all the way to the top of the carb."  He designed a very simple tin plate that goes on top of the carb and covers up, oh, perhaps 40 % of the carb. Again the purpose is not really to restrict the carb, but to sort of make the top of the carb the same size as the bottom of the carb. He also did a some jet changes and corrections, my jetting changes involve 130 main jets in both carbs. I still use the factory airbox, this man put on a pair of Uni foam air filters. Yes, my YICS is still on.

In computer terms you may call this a "work around" clean carbs (and of course I have cleaned my carbs several times and run a big gas filter) and the Yamaha fix are the recommended methods but for ME anyway, this "work around" works well, I have no dead spots, only a power band from idle to 10k. I have noticed in the last year or two that I do not seem to get the MPG I used to get, but the bike runs so good I'm not real interested in playing with it-plus I think I drive it harder and faster and that's part of my problem.

Anyway, another two cents worth!         

[YellowJacket!]

From my experience, JB Weld does not hold over time.  It seems too brittle to handle the expansion and contraction associated with the heat and increase and decrease in pressure as it operates.  I tried JBWeld twice and both failed within 6 mmonths.
My current way..and longest lasting, is to use a sharp utility knife to score along the seam deep enough to split the two halves cleanly...takes longer than the saw but yeilds a cleaner edge.  Then I sand the edges down with coarse grit sandpaper on a flat surface.
I made a gasket by drawing an outline of the YICS and cutting it slightly larger (about 1 - 2 mm) than the YICS walls, including the wall separating the chambers.
I then ran a bead of red RTF around the entire edge, including the center, of the YICS and placed teh gasket down on it.  repeated for the other half and clamped the two halves together for 24 hours.  6 mmonths later, still tight as a drum.

I'm one  of the beleivers in the YICS.  My bike just seems to run better with it and when its not working, its more than obvious.  When it is working, it idles lower and better, returns to idle more quickly and seems to acceleratte better.  Its one of those things thats gonna always be subject to debate but I think it was put there for a reason.

David

[Rick G]

YJ , I have done basically the same procedure, except I used Yamabond to seal it . I made a gasket on the first couple, but concluded it wasn't necessary and omitted it on later YIKS boxes.

[Kid Jedi]

I love the support and info available on this forum, but I still don't believe the flapper door, I still thik that with proper calibration the bike would run better with out it.  Now we could go on for years discussing this but i need some honest to god proof before I can make a good counter argument so the ball is in my court till i get some conclusive dyno testes done the tests would include torque, horsepower and fuel air ratio of the bike. so it would conclusively close the case on this issue.

Who knows I could be full of crap, but I look forward to finding out!   ;D

[funkamongus]

mine is off for now, I might as well do it, too. so, split it cleanly, yamabond it back together..what is the gasket material you used? YJ?

[funkamongus]

what gasket material, did you use for the side cover, kid?

[inanecathode]

I love the support and info available on this forum, but I still don't believe the flapper door, I still thik that with proper calibration the bike would run better with out it.  Now we could go on for years discussing this but i need some honest to god proof before I can make a good counter argument so the ball is in my court till i get some conclusive dyno testes done the tests would include torque, horsepower and fuel air ratio of the bike. so it would conclusively close the case on this issue.

Who knows I could be full of crap, but I look forward to finding out!   ;D

What is there to believe about the flapper door, how exactly do you posit it hurts performance or are you just making a baseless statement you hope quantifiable test results will back up? What's your basis for argument? That the now wide open at full throttle flapper door which poses maybe an air restriction amount totaling less than a square millimeter would significantly affect performance if it was removed?
I'm not one to follow manufacturer-is-always-right dogma, and i can wrap my head around the school of thought that every single emission control or seemingly emission control device on a vehicle hurts performance and must be removed, but you have to at least have some critical thought about the component before you assume its a waste of power or weight.

[Kid Jedi]

The flapper enriches the fuel to air at the low end, by limiting air. all carbs, even those mikuni downdrafts can handle the fuel requirement of that vision, if tuned properly. back in 82 they used exhaust gas sensors to determine settings for the carbs. with that kind of equipment it would be easy for joe six pack to match the fuel air to 13.5 to one by guessing and checking with various jets so either the carb guys were out to lunch or there is some other reason. motorcycle emissions regulations are slippery, in that  motorcycle are not measured individually but as a product line, in that the average is taken from all of the v twins that Yamaha made those years. so in say the 0 to 1/8th throttle range the average of the virago/vision line the virago were a little too far out of the emission spec. to fix this they can either gut the power from the successful virago line, or let the vision take the hit. Which is why the flapper doors exist. My source: professionally certified tech with 15+ years of experience removing things just like that flapper door from all kinds of bikes for track use.

[The Prophet of Doom]

People will say all sorts of stuff about visions.  Sometimes it's backed up by their own knowledge and experience; others not so much.    There are enough contrary opinions here to make you realise that just because method A works, does not mean method B will not work equally well, maybe better.

I would encourage you to play to your hearts content, and let everyone know what works and doesn't work for you. 

My V has no YICS, no flapper, no airbox (pod filters) and a baffleless exhaust.  It seems to run pretty well.  It does have a flat spot, but nothing I can't ride around.
Good idea on a dyno run for jetting, I would be interested in seing your output as I believe these bikes can do way better than stock.  A dyno run will help you jet for max power, but won't tell you about dangerout lean-outs.  You really need to consider drilling the pipes for a couple of oxygen sensors.

[YellowJacket!]

heh heh heh... I think I'll buy Lucky a month of internet access to chew on this one.  ;-)

I think in part, it's a combination of carbs that were just too big for the bike and having to meet emissions standards of the time.  You are right, they were probably tuned for a specific range...obviously not 4000 to 5000 rpm so the vacuum actuated flapper was added to cut down on the airflow to make it run better and not stumble.

Today, with the right tools and a box of jets and a lot of time, yep, you probably could figure it out and run it without the flapper.  Would it be worth the effort in the end?

David

[The Prophet of Doom]

Definately worth it
http://www.youtube.com/watch?v=2Xz4DakOksQ&feature=channel_page

[funkamongus]

whoa, sounds GREAT!!

[Kid Jedi]

well i am also updating the vision to fuel injection. so truly testing the yics and flapper door are NOT to far out of my way. since i will already have a pair of wide band o2 sensors on the exhaust

[inanecathode]

Okey dokey then.
After you're done fixing a massive multinational corporations conspiracy to make the vision run like shit from the factory, and install totally custom in every way fuel injection and electronic ignition, maybe you can come fix my time machine so i can buy up a bunch of rz500 parts in 1986.
Good luck with the vision adventure.

[Brian Moffet]

Okey dokey then.
maybe you can come fix my time machine so i can buy up a bunch of rz500 parts in 1986.

Sounds like you need a nap  ;D

[akvision]

Inane! 
Wisdom and experience will prevail. Experimentation is part of evolution. 

I value your judgements.  Others have to try, and will learn.

I belive in the YICS!  As stated in earlier posts.

Discussion is what it is all about, and some new ideas too.