YICS

'Without' seems to make more sense but I'd be the last to question those engineers. Still, this guy has had 6 XJs over the years and shares Wizard's point of view.

Are bikes tuned differently in the southern hemisphere? Water drains from a sink differently down there, no?

 

It is impossible to argue a contrary point of veiw with someone who has an inherent, vested interest, resulting in dogma.

 

No, the sun is still shining, (maybe not from any orifice of mine, though.)
What you have to take into account is, why the engineers developed the YICS, it was to try to produce a cleaner burning engine to meet with the, then new emissions controls, the results were arguably mediocre.
If one was to be cynical, you could say that is was a marketing ploy, an attention grabber for the "tree huggers" of the early eighties.

 

Could be.

Or perhaps it's hard to fool Mother Nature, or Father Physics.


IF----and we'd have to agree on definitions first and foremost, or we simply will continue to degenrate in the realm of "opinion" (and like other orifice's, everyone's got at least one or two of them)----if the definition of "synchronization" means:


1) an equal power output or equal power contribution from each cylinder


Then tell me, slowly and exactly, how you would measure this equallness except via the vacuum signal from each individual cylinder?


And, if that indeed IS the definition of synchronization, then how can an individual cylinder vacuum signal be measured when there is a wide open passage that connects each intake port to all others, and whose sole purpose in life is to SHARE vacuum signals between all the cylinders?



2) Now, if that is not the definition of synchronization, then tell me what is:

Sounds like cynical dogma, perhaps?

 

Don't clean the carbon out of your YICS passage and don't worriy about it. The XJ1100J (36000 miles ) I was working on today was plugged so I guess its like a non YICS engine now. synced right up . The only thing I can say is with totaly rebuilt carbs it runs GREAT. Too bad about my 2nd gear though but in 3rd she pulls real hard.

 

It runs as a 4 cylinder UNIT not 4 individual cylinders.

 

A unit is the sum of its component parts though.........

What is the purpose of "synchronization" if it doesn't apply to the INDIVIDUAL cylinders?

Why even "synchronize", then? Even non-YICS engines are supposed to be synchronized, correct?

Via measuring the strength of the vacuum signal from each INDIVIDUAL cylinder?

And then twiddling screws and mashing buttons and standing on your head while juggling BB's with your toes and consulting your OUIJA board to determine how to proceed?

Or by adjusting butterfly shaft openings on INDIVIDUAL carbs so that the VACUUM SIGNAL from each INDIVIDUAL cylinder which measures the theoretical POWER OUTPUT from each INDIVIDUAL CYLINDER is equal to all the others......thus resulting in "synchronized cylinder outputs", and thus a "synchronized entire unit"?


And how can the above be done when there is a big vacuum LEAK between all the cylinders?

 

I understand.

 

You know what would be REALLY interesting? If someone were to take a YICS head apart, take it somewhere and get the YICS passages welded up and the ports ground smooth again, NOT doing any extra "porting and polishing" and just SEE if it really makes any difference, performance-wise. Wiz may very well be right in that it was more marketing device than engineering breakthrough; but the simple bloody fact of the matter is it exists. And it really IS exactly what Len finally described it as: a massive vacuum LEAK between all the cylinders. All the more reason to plug it off for tuning, at least for vacuum synchronization.

Which raises this question: Since using the Colortune is the final mixture adjustment phase, shouldn't the YICS be unplugged because the cylinder in question will be drawing its mix from the other 3 also once in service? Remember Yamaha never intended for us to be fiddling with the mixture screws so they don't tell us anything about that part of the procedure. When they used the EGA did they use the YICS tool too? Or is it only for vacuum sync?

 

That is a wonderful question. The 1981 Yamaha Technical Training manual is pretty silent on that issue, except for two passages.

The first one deals with "Tuning For Gas Mileage", and the procedure reads:

"With the machine properly tuned, run the (EGA) idle check. Adjust the mixture screw until CO for each cylinder is approximately 1/2% less than the recommended specification. Be sure to pay attention to engine speed and carburetor synchronization. They must be constant during all adjustments."

They then go on to caution that such a setting---for improved fuel mileage---should yield increased gas mileage with "no hesitation coming off idle", but, that such a change will require "longer choking during cold starts".

It should be noted that elsewhere in the manual, they note that a low CO reading at idle is symptomatic of a lean engine condition.....and above, they are basically telling you to shoot for a Low CO reading, meaning they are telling you to purposefully lean the idle mixture setting.


The only other place that, again, indirectly mentions the issue at hand is in the table/chart of Idle CO/HC Specifications by model, by year. Under the 1981 XJ550R/RH listing, in the HC column for this bike (and this bike only; there is no listing for the XJ750RH model, for some reason.....), the specification called for is 500ppm max HC, with an asterisk noted, and the asterisk note reads:

*With YICS Shutoff Tool


Since synchronization requires the use of the YICS blanking tool, and the CO/HC measurements on the 550 model specify the use of the YICS tool, and the mixture screw changes and measurements require carb synchronization to be "constant during adjustments", then my vote is that they expected the service tech to keep the YICS tool installed and activated within the YICS passage during idle mixture screw adjustments.......akin to adjustments made via a Colortune plug in today's world.

 

Another downside of the YICS port is, if there is an air leak in one boot, say, then all 4 jugs will be effected, leaned out.
It has to be said that Yam' engineers would have to advocate the use of the tool, or they would be admitting that the YICS port is doing nada.

 

Ok gentlemen I,m a newbe to the YICS motor but it seems to me that if you sync the carbs with the tool it would be way off when you pull it out. Due to the fact that you now have a four port vacuum leak. Has any one check the carb sync without the tool after sync with the tool. My experience in syncing two or more carbs on a car if you introduce a vacuum leak into the system it screws up the sync between the carbs. It only makes sence to me if we run the bikes without the tool in it then it should be sync'd without it. I may be wrong?????

 

I could see how its working at High Speed. That would make sense. The port would make sure no bit of mixture is lost. But at Idle, it cant really compress anything, there isnt a whole lot for it to do! Since my bottles didnt work I'm going to Elec sync without, and weeks down the road I'm buy the tool and do it with.

 

The all-important asterisk! I think that one asterisk makes it a pretty DIRECT mention; they're giving us the EGA specs and telling us the tool is in use to obtain them.

YICS tool for Colortuning it is.

Wiz raises a good point about Yamaha advocating use of the tool to give credence to the effectiveness of YICS; but I honestly don't think Yamaha would have gone to all that trouble just to foist snake oil on us. I think they sincerely believed in it, and I think it did its job or they wouldn't have clung to the technology for as long as they did.

The irony in all of this is the fact that we are doing our level best to UNDO Yamaha's actual intent with YICS, to make the motors run lean (and therefore cleaner.) They wanted them on the ragged edge of too lean, we're striving for nice and fat rich blue flame.

What do you want to bet that a motor tuned using Yamaha's EGA specs would NOT burn "bunsen blue" if you checked it with a Colortune?

 

You know, I read somewhere (and darned if I didn't copy it or save a link, or if I did, I don't know where!) that, of course, the reason that we in the USA didn't get the XJ750-X (water-cooled 5-valve engines) was because of the "Harley" tariff, to protect their bigger engined bikes form "illegal and opportunistic dumping" by the foreign (meaning: Japanese) manufacturers of large-displacement bikes into the US market....which was supposedly killing HD (and HD was on the verge of bankruptcy at about that time). So as a "Buy American!" political favor, a tariff was issued, and the rest is history.....

But the interesting note was this: in that era, before HD got its "cult status", most bikers realized what was REALLY wrong with HD: their products were old, dated, over-priced, etc. Their engine technology and performance was at least 1-1/2 generations behind that of any foreign manufacturers, especially Yamaha; they were clinging desperately to the old pushrod engine design that was state of the art back in...what? the 1940's?. In fact, it was claimed that Harley engineering actually took apart some of the Yamaha engines to study, and concluded that Yamaha had perfected a method of mass-producing what amounted to basically blueprinted, almost race-ready engines for street use (obviously something the buying public had also figured out a while back).

So, although those Yamaha engineers may have been too slick and clever and cunning and deceptive to properly design a YICS system, maybe it was because they were just too busy pumping out advanced race-like engines for street bikes instead?

 

I never said YICS wasn't "properly designed" I'm just agreeing with the possibility that it wasn't the engineering marvel it was touted to be, but more of a way to "band-aid" for tighter emission specs.

It obviously WORKS; but what difference does it REALLY have? Performance alone? The jury is out.
A cleaner-burning motor? QUITE PROBABLY.
A cleaner burning motor that didn't have to sacrifice performance to that end? **bingo**

Oh, and Harley's basic (original) design dates to around 1907. I'll bet a lot of folks aren't aware where the "potato-potato" exhaust note comes from:
"Original" Harleys' (not the V-rod) cylinders have a COMMON crankPIN, the connecting rods share it, one is "forked" on the end and the other fits in between the legs of the fork. So the cylinders have to go "bang-bang--wheeze-wheeze" instead of "bang-wheeze-bang-wheeze."
Which explains why they have such a low redline.

 

Yes, the old single-pin crank design is also used on may Yamahas, Hondas and Kawasakis now. It gives that "potato-potato" sound that most like (me included) which I don't get from my dual-pin crank on my 1100 Shadow Spirit. The 1100 Ace has the single-pin crank, but makes less power, so there is a price to pay for sound I guess.
Makes you wonder why Harley never tried the dual pin crank design and got more horses/rpms out of their motors? Just a thought.

 

From my reading of the Yamaha literature on the YICS system, it was designed as a FUEL-SAVING measure rather than as a performance enhancement or emission-control system (although, of course, all three issues are inter-related). The marketing guys pump the "10% greater fuel economy without any other changes" while the engineering types ramble on about the volumetric efficiencies that accrue from swirling fluids creating better cylinder filling and better burn rates (all of which, by the way, I feel is absolutely correct, true, and a pretty basic, accepted tenet of combustion system design).

Motorcycle magazine test reviews from that era seem to verify that, as they comment on the addition of the YICS system, noting that it adds almost no performance benefit but does increase fuel economy by a measurable amount AND reduces or virtually eliminates the off-idle transitory "stumble" that seemed to be a feature of the pre-YICS engines (which might explain why the pre-YICS people recommend tying together all four intakes with rubber tubing and t-fittings on the intake manifold vacuum ports, in effect creating a simplistic version of one feature of the YICS system).

The non-YICS guys modify their engines to mimic a YICS design; the YICS guys weld-shut their YICS passages to eliminate it.

What is the world coming to?

 

Hey now, I'm not advocating welding up YICS passages, I just wondered WHAT it would do?

Come to think of it, my Norton has a "balance tube." It's a piece of tubing connecting ports (just like the XJs vacuum ports) on top of the intake manifolds to each other. Primitive "NICS?" I do believe it is...

D; I believe Harley DID shed the common crankpin in favor of more HP, don't they call it the V-Rod?

 

Welding the passage closed just to see the effect seems a bit uneccessarily extreme. Why not just do a dyno run with and without the blanking tool installed? That will at least tell you about the performance, and potentially, depending on whether you're checking 5-gas, the emissions effects.