YICS

I'm getting ready to fix up one of my old bikes, my '83 maxim 550. I'm sure many of my questions will seem elementary to veteran xj owners. Anyway, can someone tell me what the YICS does exactly? It stands for Yamaha Induction Cam System? Is that right? So, what is it?

 

Yamaha Induction CONTROL System. It's a series of interconnected passages that lead to small ports behind each intake valve. When an intake valve is open (and the others closed) the incoming charge to the "closed" cylinders helps feed the open valve through the little YICS port. This fast-moving "addtional" intake charge serves to swirl the mixture as it enters the combustion chamber. Yamaha claims it increased fuel economy and performance; they left out the emissions-lowering benefit, but that was probably as much behind the design as anything.

Does it work? That debate can go on for pages. I can tell you this: The YICS ports on the 550s are considerably larger than they are on the bigger YICS bikes for some reason. I've GOT to believe they have some effect, just based on the performance of the 550 Seca, while still getting over 50mpg. I've never tried to ride my bikes with the YICS blocked off though.

The biggest "issue" in regard to YICS is an ongoing debate over whether or not the block-off tool is truly necessary for proper carb tuning. The factory says it is; personally I believe them and my own experiences have proven it. Others have VERY different opinions and will jump in I'm sure.

 

Thanks for the info. It makes sense now. I still don't understand why I need to shut it off to sync the carbs, though. Do I have to get an actual yics shutoff tool? Is there a way to fabricate a homemade yics tool somehow?

 

You and half the folks on this board.

If the YICS isn't blocked off, you're trying to adjust one cylinder but it's being FED by the OTHER THREE CARBS (at a lesser volume to be sure, but still being fed.)

I have a 4-stick manometer; so the last time I sync'ed, just for poops-n-giggles I tried doing it without the YICS tool first. I WAS able, after MUCHO fiddling, to get the carbs apparently sync'ed. Then I popped in the tool and found out that #2 was WAYY off and I had compensated for it with the others. Adjusted 'em all correctly with the tool IN; then checked again with the tool out and they were right on.

Yes you can make a tool; there are any number of web links and homemade solutions out there. The biggest problem is sourcing high-temp tubing for the seals; it's easy to spend more than the cost of the tool trying to make one.

chacal carries them for like $39. I made one and melted it; then bought one. You really do need to use the tool to properly sync a 550.

 

i'am sorry sir but that defies my logic

 

Pics of a do-it-yourself YICS tool are in my gallery and available in our Do-It-Yourself Links page. Just be sure to get the right size hose (my pic is for 650/750 apps) for your 550 as BigFitz mentions.

 

i'll be building one of these YICS tools eventually, kudos Robert, those are the nicest looking "plans" for a YICS tool i've seen to date.

I do have one question, however. is it really necessary to bend the threaded rod? i was thinking i could lock a couple nuts together on that end and use a wrench to hold it while i tighten the wing nut. or is the handle necessary to be able to pull the YICS tool out when you're done. does it get pretty snug in there?

 

Why don't you build one with the latest refinements?

 

OK. How about this. Rather than checking the vacuum on all four carb holders, you just check two, and attempt to synch the four carbs by what you read from two of the intakes... sounds crazy, right?

Well, when you don't have the YICS passage blanked off, any single vacuum port is showing you a vacuum value generated by combining the draw of its cylinder and at least the one adjacent one (for #1 and #4 that have only one neighbor). The whole point of having individual vacuum ports is so you can tell how much draw each cylinder is generating; leaving the YICS passage open blurs those vacuum values so that too low + too high could look the same as just right + just right.

That's my understanding of it, anyway.

Cheers,
Paul

 

If you have a couple of hours to spare you could always read THIS thread. :lol:

 

Thanks but I have to give credit to the author of the picture in the link mentioned. I simply cleaned it up and added my 2 cents worth based upon my experience with his/her picture.

Nope, you can do as you like but I must admit, I was pretty stoked when I got to play with my propane torch.

Yes and possibly. A bent handle is easier to pull wouldn't you agree? And it may get snug if the rubber inserts melt on you! Be sure to source silicone hose as mentioned.

 

Thanks for your suggestions, everyone. My only question (keep in mind that working in this particular bike is relatively new to me) is if I make my own, how do I know for sure when it is working correctly? How do I know if the yics is shut off?

 

What I observed was the "clouding the results" as SQLGuy explained. Sync'ing without the tool I was able to produce a "falsely balanced" condition that appeared to be OK. In fact, the carbs were NOT balanced, but 1, 3 and 4 were "masking" #2 via the YICS passages. Once "truly" sync'ed (with the tool) and then checked with it out, they still read as balanced because they really ARE now.

Sync'ing without using the tool CAN produce false results, you can fool yourself with YICS' help.

 

There is an observable difference in the way the motor will run with the tool in and engaged vs. out. The actual differences vary (higher or lower idle, rougher or smoother etc.,) depending on the state of tune to begin with; but you will notice a difference. If you put your tool in and there IS NO discernable difference, doubtful it's working.

If you DO decide to make your own tool, be sure it also seals tightly against the side of the cylinder block to prevent a vacuum leak. And remember, that area gets hot too.

 

Sqlguy, try this, 4 leg parallel circuit (1)5k,(2)5k,(3)6k,(4)4k, 3 can never =4
balance the currents in each leg

 

and then

and then

so after one removes "the tool" and the idle changes for better or worse
should the difference be compensated for or left as is, because it was done with "the tool"

 

Obviously, for each leg to draw the same current, each leg must have the same resistance. However, my point is that to check that (or to check the vaccum of each cylinder), you need to be able to measure them independently. With the YICS tool out you are not measuring individual cylinders, but combinations of them.

If you can only measure the combined current draw of 1/2 and of 3/4 can you tell the difference between:

(1)5k,(2)5k,(3)5k,(4)5k

and

(1)5k,(2)5k,(3)6 2/3k,(4)4k

?

 

your measuring resistance and i'am measuring current
where did you get the extra 2/3 for #3 there is no extra at a given rpm as one goes up the other goes down
i would have thought that in your micro-squirt project you would have tried without a blanking tool once or twice just for the sake of convenience

 

For a parallel circuit, as you've specified, current is proportional to resistance. It doesn't matter whether you're measuring current or resistance, they are directly tied and to change current you have to change resistance.

5k in parallel with 5k is 2.5k.

4k in parallel with 6 2/3k is 2.5k

If you can't measure 1 and 2, and 3 and 4 separately, you can't tell the difference between the balanced 5k/5k and the unbalanced 4k/6.66k.

Same thing applies in carburetor balancing. If you can't measure the draws of the individual cylinders seperately, you can end up with an unbalanced configuration that looks balanced. It will even work just as well as the balanced setup at idle. It's when you open the throttle and start drawing more air/fuel and transistioning from pilot jet to needle and main jet that things don't work as well as they should.

Microsquirt runs two injector circuits, so, even if the stock firmware allowed it (which it doesn't) there's no possibility to trim individual cylinders on a four cylinder engine. I am now running MS2/Extra alpha code, which does allow cylinder trim, and I am using that to lean the inner pair of injectors by 5% to make up for the extra mixture 2 and 3 can steal from their neighbors. This matches (more or less) to the stock Yamaha leaning of the inner pair of carbs versus the outer pair on YICS bikes; and had also served quite well to even out the color of the four plugs. Also, I'm using a single throttle body, so no real individual synch is possible.

 

we seem to be stuck on not being able to read each carb separately
when really we are, from the butterfly to the vacuum port there is nothing
and there is no measuring, you compare and equalize 3+4 then 1+2 then
(1+2) and (3+4)
so we have "measured" all 4 separately in relation to the position of the butterfly, and thats all we can control, other than valve lash
as far as the parallel circuit comparison, a 4k and a 6.66k would be obvious no matter what pair it was on
[/quote]If you can't measure the draws of the individual cylinders seperately, you can end up with an unbalanced configuration that looks balanced. It will even work just as well as the balanced setup at idle.

 

I have no idea what you're talking about here. If all the carbs are connected together by the YICS passage, then how can you be measuring them separately? The fact that the vacuum port is between the butterfly and the YICS port doesn't mean that the YICS port has no effect. It's still effectively a vacuum leak between cylinders.

What?! You mean if you were looking at them or what?

Let me break this down further:

Let's say we were using 10V for your parallel circuit. And, let's say we're using variable resistors, since that's a better analogy to the carb balancing behavior.

Since you can only measure 1/2 and 3/4 as connected pairs, you do you best and you end up with:

1=5k, 2=5k: this pair of parallel resistors is equivalent to 2.5k and therefore draws 4mA.

and

3=4k, 4=6.66k: this pair of parallel resistors is equivalent to 2.5k and therefore draws 4mA.

Either pair, which is all you are allowed to measure (because you didn't isolate them like the YICS tool would do), would draw the same 4mA, so how is the 4k/6.66k "obvious"?

So it's 91 times smaller... so what? Consider that you're balancing carbs at idle, with the butterfly 99% closed. That 91 times smaller hole is pretty close to the size of (maybe even larger than) the gap between the butterfly and the carb wall through which air is being sucked.

 

did i mention that i LOVE analogies? anyhow, i drew this schematic to see if my understanding is correct.


since the cylinders don't all draw exactly the same vacuum, V1 thru V4 are all different, right?

synching the carbs is equivalent to adjusting the values for R1 thru R4, right?

is the goal to get the current flowing through all resistors the same?

would a perfectly tuned engine have 0 volts across the YICS resistors?

am i stretching this analogy too far?

do i have too much time on my hands?

 

I think your analogy is quite good, just one thing the 'voltage' or pressure difference over the YCIS wound not be 0 in a prefectly tuned engine because all the cylinders are not drawing in air at the same time. Basically which ever cylinder was on its intake would have a lower potential then the rest and as such it would recieve 'current' from the rest.

Also I believe that in your circuit diagram you should have your YCIS resistors going to a common node and not to the adjacent cylinders but that might be getting a little too technical. (The common node would represent the large - in relation to the passages - YCIS bar the runs along the engine).

I think it is also important to remember that only one cylinder is going to be drawing in air at a given instant. So you would really have to do out 4 drawings

 

I get the impression that the YCIS tool is there because all the cylinders don't draw at the same time. Basically I think that the YCIS ports allow vacuum to be drawn from the other cylinders so that things can appear balanced when they aren't. I think that if your vacuum gauge could give you a reading right as the cylinder is on the intake you wouldn't need the block off tool. But because the tool only takes an average reading the vacuum that leaks in from the other cylinders over time you can't do a proper balance without the tool - though you can get things pretty good.

What I'm trying to say is that what you want to balance is the vacuum during the sort period of time when the cylinder is drawing in air. However, because of the way the gauges are you just cant get that measurement - basically you just get an average reading of the vacuum during the time from one intake to the next. So if you have a small passage like the YCIS passage it can't allow enough air during the intake to allow things to balance, but when the cylinder is not on the intake and there is almost no airflow it will allow for vacuum to leak from the other cylinders that are on their intake. So even though the cylinders may be unbalanced during their intake period the gauge may still get a reading that looks balanced because of the vacuum leaks between the cylinders.

Anyway thats just what I was thinking - obviously I'm not a Yamaha engineer so I'm just guessing but that seems to make sense, in my head at least =p

 

Exactly. Except it's not just a "vacuum leak" it's an uber "leak" being PUSHED by the charge from the other 3, which is exactly what YICS was designed to do. Which is why you need to block it off to get an accurate sync.

 

my understanding is that installing the YICS tool is equivalent to removing the YICS "resistors" completely - so that there is no path for "current" to flow between cylinders.

the thing that gets my head spinning is that that the circuit diagram makes a lot of sense thinking in terms of DC. but the reality of the situation is that they're all AC.

i'm assuming what we have is a "4"-phase power scenario where all the "voltages" are 90 degrees out of phase with each other.

skeeter: will now admit he took some electrical engineering classes and is happy to see a useful representation in terms he can understand.

seems now that the YICS tool debate can, in theory, be settled mathematically. (maybe if i get ambitious, i'll write some equations - but fact is: riding the bike is exponentially more fun.

 

Thank you all for awakening in me my long ago training as a radar repair technician. The electrical analogy is pretty good although it is DC current, only with an on-off switch (the intrake valve).
After all this reading I think Skeeter finally came to the correct conclusion in the last sentence. I'm going to go have some fun.

 

at this point i think we're getting further from the point, which is
i got better results without the tool
theory is fine but until you pick up the screw driver, you'll never know
now, i'am going to go drink a beer, maybe two or three :wink:

 

Good to know.

How do you measure that you got better results without the tool? Plug chops? Dyno/AFR/5gas?

Thanks,
Paul

 

a litter of puppies took longer to die from the exhaust fumes

 

Yes, there would be 4 smaller resistors, not 3.
The YICS passage is 6MM in diameter, the 4 small transfer ports are 2 MM , or are restricted at one point to 2 MM (EXCEPT Fitz's 550)
So my math says the YICS transfer port is 8.31 times bigger than the little runners, THEREFORE the end carbs are not somehow "cheated" out of their proper charge. If anything #2 and #3 should be tuned richer to compensate for the higher heat. They are on the Turbo bike.

Didn't we all somewhat agree in other threads, that the YICS tool allows the mechanic to arrive at a proper sync quicker? And that the "new guy" could just stuff it with oily rags or just fiddle with the adjustment longer?
the "old pro" would have the tool and follow the authorized proceedure?
The time it takes to make the tool is far greater than the extra time fiddling with 3 adjusting screws.

Can't we all just get along?

 

My YICS passage is 10mm, so your math doesn't work for me.
I think the condition of the valves plays a bigger part in the process than you are all giving credit to.

 

i think that indicates you are running lean

 

Eegads Polock! You do enjoy the odd bit of humor... Don't ever change just the same, I enjoy your perspective.

 

BIG TIME. My only point in revisiting the issue was to share the fact that you CAN fool yourself with YICS' help if you sync without the tool.

Something I should point out: The sync I achieved without the tool, while nowhere near as accurate as with the tool in, was well within "specs" for synchronization. It just wasn't nearly as perfect as I got it with the YICS blocked off, and I'm a perfectionist. I could have been happy with a difference of only one or two "clicks" difference on the sticks, but using the tool I was able to match them perfectly.

 

Polock, mines running real lean,please check your mail for puppies.

 

you're right- - I converted 1/4 inch, it's 3/8.
So, 10 MM Pie Are Squared = 78.5 MM (2)
The YICS passage is 25 TIMES larger than the little runners, not 8 times.

And that statement caused a "Eureka" moment;
While using a 4 tube water filled Manometer, with or without a YICS tool, the water levels continue to shift around just a little, by an inch or 2.
What's going on? The valves rotate slowly as the engine runs and so do the piston rings. Top ring turns one way, second ring turns the other. 2 valves and 2 rings are constantly changing how they interact with the seats and cylinder walls, by a very small amount- - enough to show up as an inch difference on a Manometer. They will never stay level.

 

With my 4 tube water manometer I can get them within 5ml of each other, valves shimmed,Yics port blanked, restrictors in the air and water lines.

 

Now we are going to have PETA after us... :cry:

 

Aww, man! Now I gotta take all these puppies back to the pound?

Can we use hamsters or gerbils instead? Canaries?

Mice? White mice? Don't they sell those as food for bigger pets? That should be ok, shouldn't it?