convert your non yics engine to a yics, 20 minute job

for you that have the non yics xj's here is the site for the instructions

http:home.westman.wave.ca/~jbe/YICS.htm

(info at end of tex)
I did this mod and it works, my engine does not spit back on cold starts, has a much smoother transition from off idle and was able to lower the idle rpm to a rock solid 1000 rpm.
parts required: 3/16 vacuum hose (enough to tee back to fuel valve)
three 3/16 brass or plastic tees.
Tie all vacuum ports together with tees and tubing and back to the fuel valve vacuum port.
cheap mod for improving performance.

 

Here's my "How to convert your YICS engine to a non YICS engine."

Insert your YICS tool in the YICS slot.
Do not remove.
Ride forever.

Or better yet, throw away your YICS tool and tune your bike without it.

 

Good article on making a YICS tool.

Completely out to lunch on what YICS is and does.

It is not a vacuum balancing system. If your bike is non-YICS, joining up the intakes will not make it a YICS motor, since you will not have the ports that are cast into the cylinder heads. YICS is NOT about balancing vacuum across the carbs. It is made to promote swirl inside the combustion chamber by admitting a jet of high speed fuel and air into the port through a specially cast hole in the cylinder head near the intake valve.

Not saying you haven't improved your performance, but it is not what YICS does.

 

YICS was primarily a fuel-efficiency enhancement. It does increase power, that's why you get the same amount of HP out of a YICS engine as a non-YICS engine, but with better fuel mileage.

 

Raises one very obvious question; I would think ...

If it were a good idea to the Mod; then why didn't the Engineers connect the Vacuum Ports at the Factory?

B _ D _ D E _ (Hey, Vanna ... give them a couple of Vowels)!

 

I don't know about you, but I work on cars for a living. from what I've seen most stuff the engineers come up with is usless, doesn't work right, and usually put in a pain in the butt spot. Granted they do come up with some good ideas. but man sometimes you just want to slap them silly.

Sorry that's my 2 cents worth.

 

And if YICS was such a great idea that "increases power and efficiency" (same with Suzuki's TSCC idea), how come they don't use it anymore??

Just 80's gimmicks, methinks....

 

Bad idea or not my bike performs much better
But you are right it will not be A yics system after the mod, My mistake.
Do you know if the yics system is still being used or how long it was in production.
wrenchmaster

 

I tried connecting the vacuum ports together like that once to see what would happen but couldn't tell any difference. I don't think the little ports are big enough that connecting them will make any difference.

 

My bike has always had A very light stumble from idle to off idle even after carb rebuild,color tune, synchronization ,new oem coils and all electrical connections cleaned. When I hooked up all the vacuum ports the stumble went away. It was very noticeable.
Could be it helped the idle mixtures some what, I know my settings are not to perfection. Any way I am enjoying the smooth transition.
wrenchmaster

 

>My bike has always had A very light stumble from idle to off idle...
You probably need to adjust the pilot jets but if that fixed it and you don't have to go through emissions every year then you should be in good shape.

 

Do you mean replace them with A different size?
I am running A K&N air filter with the stock air box, Macs 4 into 2 exhaust and all jets are stock.
would you have A suggestion on pilot jet size?
BTW I do not have pass emissions here in Hampton Ga
wrenchmaster

 

usually with the k & N filter and aftermarket exhaust you have to move your jet sizes up. I'll try to find the site I was on but it gave you a formula on what jet sizes to use when changing parts.

 

Isnt that exactly what they did when they made the yics system. I know that no one has a better idea than a 1981 Yamaha engineer. :roll: It really gets on my nerves how you will be the first one to berate someones idea without trying it.

 

Tying all the vacuum ports together might very well give a better idle, as wrenchmaster's results show. Especially on a bike which may have a bit of an off-synch condition, as there is no place within a NON-YICS engine where all 4 intake tracts can share vacuum from. Tying the four intake tracts together kind of gives a "poor-mans" synch to the engine.

YICS bikes, on the other hand, share vacuum all the time. That's ONE OF the results of have that YICS passage in the cylinder head.

The OTHER result, and the one that Yamaha talks about ad nauseam in their technical manuals in regards to the YICS system, is that the YICS port that GOES UP INTO THE CYLINDER HEAD, and THEN INTO THE COMBUSTION CHAMBER, and fires a small charge of air/fuel mix into the cylinder in a "rotational" orientation, is really the main design feature of the yics system. They claim it adds slightly to cylinder filling and helps to agitate the fuel mixture within the combustion chamber slightly, or at least enough to make a difference.

Which it probably does. ANYTHING that can be done to increase cylinder filling will result in more power. If you then LEAN out the fuel mixture slightly.....you know, IN EXACTLY THE WAY THAT THEY DID WHEN THEY WENT FROM A NON-YICS TO A YICS ENGINE, WHILE EVERYTHING ELSE STAYED THE SAME ('80-1 650 non-yics engines used #50/#195 air jets, while the '82-up 650 yics engines used #50/#205 air jets, about a 5% increase in the pilot air jet size, meaing at least a 5% leaner mixture)....then as result of drilling those holes, etc. they could run a 5% leaner mixture, meaning 5% greater fuel efficiency, and produce the same amount of power.

 

Regarding jet sizing:

Here is the info regarding jetting that I found:

1 jet size for custom 4 into 2 exhaust

2 jet sizes for 4 into 1 exhaust

1 jet size for K&N filter (single inside airbox)

1 jet size for drilling out the bottom of the airbox

2 jet sizes for both single K&N and drilled airbox

2 jet sizes for individual filters

2 jet sizes for no muffler (open header)

1 pilot jet size for every 3 main jet size increase

Add up all the jet size increases and subtract one. (Remember
they go in steps of 2.0 for each jet size)

Under a mismatch condition, like individual filters and stock
exhaust or 4 into 1 header with stock filter and air box, subtract
an additional 1 jet size.

Check plug color often, sync carbs after each jet change,
make sure the floats are set correctly, and seriously consider
purchasing a Color Tune.

Make sure your carbs are in perfect working order before
making jet changes.

Additional info: Decrease main jet size one step per
2000' above sea level. Decrease pilot jet every 6000'
above sea level.

--------------------------------------------------------------------------------
EXAMPLE:

Stock = 120 Main and 40 Pilot with Y-13 Needle

4 into 1 with Supertrapp = +2 Sizes Main Jet
K&N Pods = +2 sizes Main Jet
Subtract 1 = +3 Sizes Main Jet or a 126
Subtract One More Size for Altitude of 2500' Average

I figure a 124 Main and 42 Pilot should do the trick after adjustment.

**************************

Just be aware that the issue that most affects jet sizing is the restrictiveness of the INTAKE air flow, which is via the stock airbox/filter combination. Changing the air flow on the INTAKE side of the engine requires much more of an increase in fuel delivery requirements (jet size) than it does versus merely changing the EXHAUST flow by itself; doing both changes together may or may not have "additive" effects, depending on just how restrictive the aftermarket exhaust system is----and especially, at what RPM range(s) does that restriction occur at? Not all aftermarket exhaust systems are THAT much less restrictive than the stock factory 4-to-2 system.

The 650 K&N filter probably passes more air than the stock paper filter, although the 650 K&N filter is a TINY little filter for some odd reason, so the reduced (like, about 50% reduced) surface area of the K&N filter versus the stock paper filter may negate some of the "freer flowing" aspects of the K&N filter----which is why many people say that you don't have to re-jet the carbs due to ONLY a change to a K&N filter element in the 650/750 models. Changing to POD filters, on the other hand, basically means you're going to have to change jetting, no ifs, ands, or buts about it.........

The only way to know for sure is to read the plug insulators under various conditions....idle, crusing, heavy throttle, cold outside, warm outside, etc. A real pain in the rump, which is why most people don't do it, or do it improperly, and end up with all sorts of performance-related issues when going from stock to "some other" configurations. And the worst condition of all to end up with is a lean fuel mixture condition, especially at a typical crusing or bike usage rpm range, which can quickly eat up your engine, perhaps not all the way to catastrophic failure conditions, but enough to cause greatly increased heat and this rapid piston/cylinder/valve wear, and thus decreased engine performance, and do so over a remarkably short time span.

 

Cylinder head/combustion/fuel metering technology has come a LONG way since the 80's. Fuel injection, all by itself, makes a huge difference, with the precision that it affords. Cylinder head, combustion chamber, piston crown, intake port, camshaft lobe features and various other design elements make huge differences......consider, for a moment, that the highest paid (and most desired) people in the high-po engine design business (racing) are the cylinder head and cam designers/builders/tuners.....

In the 70's and 80's, the max compression ratios you could run "on the street" was 10 or 11:1, and that was on better gas than is available now. Hi-po engines of today run 11:1 or better all day long, on fuel that is remarkably lower octane. Why? Better cylinder head/combustion design is the primary reason. And, much better fuel efficiency for the power produced......and remember, all other things being equal, better fuel efficiency is a RESULT OF higher power output. Burning more OF the fuel introduced into the cylinder is the key to power output.

The "shortcut" way to more power is simply stuffing more fuel into the cylinder (richer mixtures), which is certainly easier to do, but has its own set of drawbacks in the process of doing so.

 

Thanks Chacal for finding that thread. Hey Gearhead no need for looking up that thread but thanks for the offer.
I love this forum.
BTW Chacal thanks for the support and the information, that explains the YICS system very well.
wrenchmaster

 

i think i might try this vacuum connect mod tomarrow i will report findings.
i am always looking for better fuel efficiency.

 

Wrench, you're very welcome!

Blue.....let us know, although again, tying those vacuum ports together may make your bike idle/off-idle performance a little smoother, but it's questionable whether it will result in better fuel efficiency. Tying the ports together gives you a "backyard, all-of-the-time" synch effect (sounds good on paper, but it's the wrong way to accomplish a synch for a variety of reasons). YICS promotes combustions chamber filling/mixing, and that's where the additional power comes from. Synching and cylinder filling are two different (and here's a monkey-wrenchmaster in the works for you!: "but inter-related") things............

 

well i did this mod on my lunch break it starts, idles, takes off,runns and accelerates alot smoother than it did. it was already synced up pretty good, this feels like iceing on the cake. i guess i dont realy care if it gives me better fuel eccomomy, it feels great. BUT i am pissed at myself because i droped the tank and put a flat spot on the top right curve. (any one got a good tank at a good price) but it was already dented on that side and it isnt too bad. all in all it is cool to have tryed his mod.

 

Well, I tried it too. I've very recently done a valve job, sync and colourtune and sync some more. And I was running pretty good - easy to start, decent idle, no flatspots. After making the mod, I seem to have a stronger idle, faster takeoffs and just generally better performance. for the few dollars and few minutes it took, it was worth it

 

accel at speeds is much more powerful, i felt much less vibrations, the only thing i noticed that was not a total plus was there was much less engine brakeing, but i think this will give me a little bit better gas milage. i will let you know tomarrow as to whether or not there is a change in gas milage.

 

The Vacuum Port Link-up isn't going to be TRUE YICS. This we know.

But for less than 5-Bucks for everything you need ... and, being able to switch-back to Normal if the experiment doesn't work-out ... then, how can you go wrong?

I don't really know what the net effect will be.
It "Seems like" there would be a Balancing effect -- In theory.

With nothing to lose ... if someone is willing to try this and submit a "Before and After Report" ... then, why not see what happens?

I don't think it will substitute for actually Synchronizing the Rack as you do with the four separate and pulling the Intake Stroke Vacuum.

But the experiment is cheap and harmless and if you want to try it to see if the Bike will run better we won't say no!

How's does that work?

 

ok Rick
here is my report:
before --Good
after-----Very good
wrenchmaster

 

Fine.

Then, take it a step further. Fine-tune the Pilot Mixtures with the Vacuum Lines linked-up, too.

Read the Plugs and see how their Coloration is.
If they are too light; add a couple of DEGREES of Richness by Tweaking the Pilot Mixture Screws out the width of a Nickel.

To Dark:
Go the other way a couple of degrees.

But, don't do them all IF only ONE needs the tweak.
Read the Coloration on EACH Hole and tweak EACH Hole individually AS NEEDED!

 

A good idea Rick, I am always looking for a finer degree of tuning.
My idle mixture screws have the coarse threads rather than the fine threads found on 82's and later so turning my mixture screws changes the metering with a lesser degree of turning than the fine threaded ones, they are very sensitive.
First a new set of plugs and you will have a report.

wrenchmaster

 

Balance tubes are nothing new and help idle smoothness. YICS added the inlet port to promote fuel suspension.

 

You will not get a consistent sync.

The passages are cast in place, not machines. There are slight variations in volume in the passages, slight variations in the intake runners, and slight variations in each carb.

To see the magnitude of these combined variations balance the carbs without the YICS tool. Get all the little columns equal.

Now install the tool and start the engine. The variation between the columns is the cumulative effect of the small differences.

You can get close but it won't be spot on without blanking the YICS passages.

 

Injuhneer, some of us been down this road before, some of us agree to disagree, and thats ok too
if you sync with the tool in then remove it the sync changes and the carbs are no longer in sync, but thats ok thats what yamaha said to do.
then there are some of us (i for one) who sync without the tool and ride with the carbs in sync
but i am flexible, maybe i'll try the tool again just for the sake of science

 

On vacuum balancing:
I was really bored, so I inter-connected the vacuum ports on my 750 that -has- YICS. I saw a noticeable improvement at the low end - the bike has more take-off power. Nothing much in the top-end department though. Still, I'm gonna leave it on for a while to see how it affects mileage, etc.

On the YICS tool:
I found that if you have a set of four gauges (dials or sticks, doesn't matter), the YICS tool is more of a nuisance than a helpful tool. I consistently get smoother idle tuning without the tool. When I used 1 or 2 gauges to sync, the YICS tool helped a lot, since I didn't have to switch the gauges back and forth quite so much to see how one adjustment affected another.


...just my 0.46 Rubles (that's 2 cents U.S.)

 

i picked up 3 miles per gallon with this mod all around happy with the difference

 

That reminded me of this:

http://journeytoforever.org/biofuel_lib ... h/me3.html

I saw a web page (some years ago) where someone had modified this idea onto a GS850 Suzuki and was impressed with the results. You could easily connect this through the vaccum hoses on an XJ's carb boots.

 

Any more reports on this? IIRC, mountain sled from teh 90's had something similar done to it from the factory.

 

what does yics stand for?

 

I also connected my vacuum ports together, and i am really happy with the results. Faster starts, no popping at all, good strong acceleration, smooth running engine, awesome modfor under 5 bucks. Great mod. Very happy.

 

A balance chamber on the intake. YICS (Yamaha Induction Control System), a fuel-saving engine system, was developed for 4-stroke engines. (from the Yamaha website)

Yamaha does not make the tool anymore, I bought mine from Mike Oberle, but here is a DIY kit.

http://www.crc2onlinecatalog.com/yics_tool.htm

 

i needed new caps on the vacuum ports, so i tried this mod and to be honest
with you i can see no difference at all but i wonder what it's doing to the petcock vacuum diaphragm, if anything it's going to make sync'ing a little more complicated

 

sorry to refresh an ancient topic but when I read this I had to comment. I'm sure what follows has been said elsewhere.

I read all three pages of this and I'm a little shocked no-one said the word "Vortec" even once, when describing how YICS uses the rush of another cylinder's intake charge abruptly cut off (think water hammer in old plumbing) by a closing intake valve and redirected through the passage to puff a swirly mixing effect into the stream of another cylinder mid breath.

Funky 80's technology? yes. (I have an atari dash Marty McFly would be proud of)
Bassackwards? NO.
YICS was one piece of forward thinking technology, aspects of which are being used in motor design today. The implementation was crude and imperfect yet simple and effective. There are no moving parts. In fact there are no parts at all, just a hole where other motors have more metal. yet it enables these motors to yield a better KW/h to fuel ratio than without.

 

Liquid gasoline does not burn.
Gas vapor mixed with air burns. The carbs mix gas with air, the term "atomized" is used to describe the fine droplets. It takes time to evaporate. Spray Windex in the air, watch the droplets fall for a few seconds. There's 50 intake pulses per second at 6,000 RPM.

If you had all of the air/fuel/droplet charge rotating in the cylinder during the intake and compression stroke (the whole 0.02 Seconds) the fuel droplets would tend to wet out the cylinder walls in the same way a Dyson vacuum cleaner works to separate dust.

In fact, you would want a tumbling charge with multiple vorticies, the fuel droplets being exposed to many changes in direction.

The air/fuel in the YICS system and this particular mod would have the time to fully vaporize, which produces a better burn. This could be the main effect.

When you consider a 32 MM carb being influenced by a 2 MM passage, I'm not sure how much rotation is being created anyway.

 

About 1/16th extra rotation, seems to me, from th figures available. So does that = 1/16th better fuel usage?...could be worse.

 

There is vacuum at the intake boot only on the intake stroke of the cylinder.

There is only one intake stroke at a time. If 1 is intake, then 4 is power, 3 is compression, meaning 2 is exhaust.....if I have the firing order right.

When 1 is showing vacuum at the intake, 4 has the both valves closed, 3 has both valves closed, and 2 has the intake valve closed.

By connecting all the vacuum ports together, you are making a complex plug. Think about it. The YICS bypasses the valve system, so it isn't blocked.

However, at the top of the exhaust stroke both the intake and exhaust valves are briefly open, for a scavenging effect. Remember the top of the exhaust stroke is the bottom of the intake stroke on another cylinder, and the point where the vacuum is strongest, before all the air comes in to fill up the cylinder. If the two intakes were connected, the stronger vacuum from the end of the intake might affect the beginning of the intake on the other cylinder. It would likely reduce the amount of air in a filling cylinder, due to the decrease in pressure at the end of the intake stroke, and increase the fuel in the earliest moments of the intake stroke, when both valves are open, due to the extra vacuum seen by the carburetor.

That's just a hypothesis, though. I'm not entirely sure about the amount of valve overlap. I also don't know how much vacuum differential exists between the beginning and end of the intake stroke.

 

Are you trying to say that the YICS port is AFTER the intake valve (inside the cylinder)??..... :roll:

 

Bypass is not the same as come after...it can ACT as if it was inside the cylinder.

As per the best description I've seen, the YICS bypasses the blocking action of the valve by storing energy when the valve is closed and amplifying it's release past the valve upon it's opening.
That is, it stores the energy from a cylinder's intake in the YICS passage by first creating a strong vacuum and then filling it with the post-carb mixture. Then when the next cylinder opens it's intake valve, it sucks the charge through the small passage, increasing the velocity accordingly as per Bernoulli. That high velocity charge is so close to the cylinder in relation to the intake valve that it does, effectively, bypass the valve itself, and is able to place it's own force on the charge in the cylinder.

Putting a "YICS" passage on the manifold likely can't store the energy and certainly can't amplify it to do anything in the cylinder. I wouldn't think it would do any harm though.

 

I don't know all that much about engineering so I know i could be wrong, but i was pondering the debate of whether YICS really makes a difference or not. It seems to me that it would make a difference, even if that difference is rather small. I mean if a strong vacuum is created in a very very short amount of time, as it is inside of the cylinder on the intake stroke, air/fuel mixture would be rushing into the cylinder to fill the void. When the valve slaps shut, it seems very likely that a partial vacuum remains, as air itself is matter and is fluid and can only flow so fast. The YICS seems to use the energy from the vacuum when the intake valve shuts to aid in filling the next cylinder when its intake valve opens. I am sort of unsure though as I haven't gone farther than removing the valve cover on my bike and don't know what these passages and such look like, just visualizing in my head. Anyone have any thoughts on this?

 

Actually...engines generally induct more air than would otherwise fill the cylinder at atomospheric pressure. So there is actually no vacuum when the valve closes. The technical way to say this is that the "Volumetric Efficiency" is greater than 100%. Google it. You'll like it. If you look at the camshaft, the intake closes a little bit after the piston is moving upwards again. The momentem of the incoming air allows pressure to build up even though the piston has already started compression.

You are close, except instead of "vacuum" you can say it is the "pressure" that aids the cylinder. And it doesn't help filling up at all, it helps add a vortex that assists the flame front to burn evenly and cleanly, and thoroughly to produce more energy per unit of gas that enters the cylinder. (Note: I didn't say more energy per unit of gas. There is a fixed amount of energy per gram of gas that I can't remember or look up right now. But we don't burn every bit that gets in the cylinder, and we waste some of it as heat when the flame front is ineffecient and doesn't push the piston as well as it could.)

 

Hi guys. I have been reading the posts related to this topic, and have downloaded the instructions on how to make a YICS tool.

I have a 4 clock sync setup in the garage, and before I make this YICS tool, I was wondering if anybody could explain in plain (not mechanical jargon) how to sync the carbs using just the clocks.

The reason I'm asking is because I used to have an XS750 (triple), and to sync the carbs on this, you only needed 3 clocks attached to the 3 vacuum nipples. Whatever reading was on the middle clock (carb 2, non adjustable), had to be replicated on the outer 2 carbs (1 & 3). However on my XJ900 (pre Diversion), there are 4 carbs.
Can anyone tell me how to sync these without using the YICS tool please.

Ady

 

I'm sensing two different questions here, correct me if I'm wrong.

First, you cannot (effectively) sync a YICS engine without a YICS blanking tool. This doesn't have to be a nice tool, but can be a T-shirt strip with knots in it (search around for details). It might work, but it's worth cutting up an old t-shirt to do it right the first time.

Secondly, you only need 1 gauge to sync, if you choose to use a gauge. (I assume gauge is what you mean when you say clock. If you are actually using a clock you are way off base.)

Since you seem to have a 4 gauge set up, then the process to sync it will be very similar to what you have experienced before, except you will have 4 carbs, and you have to blank the YICS first.

But if you didn't have a 4 gauge manifold.....

You need to get the reading from cyl 2, and then adjust the others to match it, one at a time. If you are using a YICS blanking tool that works well, then the other cylinders won't affect the cyl 2 much. You should still go back and make sure they are all synced, though.

Most of us use a home made manometer, filled with a viscous fluid. There is lots of information about how to make and use such a device on this forum. The reason we prefer a homemade manometer is twofold. First, it is much cheaper than a vacuum gauge manifold (what you have). Second, it compares two cylinders directly, and thus can be much more precise than a reading from a gauge.

 

Cheers for that day7a1, I had to laugh when you mentioned the clock thing......................"that's got it, they are all set to 3:47pm" lol.

Ok, here's what I did before you posted. Like I said (meant to say), I have a 4 gauge set up complete with flow adjusters (stops the gauge hand from flicking up and down), and once connected to all 4 vacuum nipples I adjusted 1 3 and 4 to whatever the reading was on 2. All 4 are the same now, and I have adjustment both ways on the idle screw. The engine runs consistently now on idle at 9000 revs, and shut off is instant when throttle is released. I don't have a flat spot now either when setting off in first, that again is instant.
I will run it like it is for a week making notes of any adjustments made if any, and then re-do the whole thing after I've made a YICS tool. Be interesting to see what difference the tool will actually make.
Once again, thanks for your reply.

 

Hey, nuube here. i am wondering if a Maxim tank will fit my '82 seca. Stupid question I know, but, I don's have a Maxim close by to try it out. Thanks in advance for the help.