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

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.

 

Sorry, got off topic. I will try elsewhere

 

It won't make any difference if you don't build it correctly and most of the plans floating around the 'net are wrong, and miss an important consideration. The tool has to seal the port it's inserted in; in other words seal tightly against the outside of the passage when in place, sealing off the passage from the outside.

Further, once the carbs are IN sync, it won't make one bit of difference. (I've tried this experiment already.)

Where it makes a difference, is in the adjusting. YICS will "mask" an imbalance, with the tool in place an imbalance cannot hide.

You can get the carbs balanced without the tool but it will take a lot longer and they will most likely never be perfectly balanced. Not to mention the frustration factor of the longer adjustment sequence.

 

"You need to get the reading from cyl 2, and then adjust the others to match it".......ahhh, i'm pretty sure it's #3
Hay Fitz, .........never mind

 

Polock... yeah, I know, I know. Don't even go there. Neverminding now :wink: :wink: :wink: And you're right, #3 is the baseline carb.

 

Looking from the back of the bike, I read the carbs from left to right (see image). #3 is not adjustable, so I take it whatever this one reads on the gauge, the others have to match.

 

Sitting on the seat, facing forward (like you are riding the bike), the left outer carb is #1, and as you move the right, you'll come across carbs #2, then #3, and finally #4, which is the far outer right side carby.

The number scheme in the diagrams above is exactly backwards!

The vacuum line from the petcock goes to the # carb.

 

My mistake, sorry chacol. I will ammend.

Diagram now ammended

 

A friend of mine had the following conversation with someone recently:
"excuse me, we're a little turned around, which way is east?"
"well, it's pretty late in the day and the sun is over there so I'd say roughly that-a-way"
"oh, we're not from around here"
*amused smirk* "just where ARE yall from then?"

And so it is with cylinder/carb numbering. The bike's number three carb will always be the bikes number three carb as sure as the sun sets in the west. Whether you happen to be lying on your back looking up at your bike or standing on your head or of in the kitchen making a sammich. They're still numbered 1 to 4, port to starboard.

Also on ANY carb bank, the baseline is the carb that has the throttle cable tugging directly on it. All the rest are tied to this one with lash compensator screws. For ours this happens to be the third from the left (second from the right) as you look down as if seated and riding. The #3

 

Sorry about the 2/3 cylinder to sync to mix up....i'm on the other side of the world from my bike and manual right now!!

 

*chuckle* so you're in that "not from around here" category?
quite alright.