Cool to block off the Y I C S p o r t s

Is it absolutely necessary block the why i c s p o r t s. Synchronize the carburetors on an 82 Seca 750 and if it is does anybody have one or does anybody know where I can get one in the Haynes or Chilton manual I don't remember which they even have a part number for it but I doubt I can still buy one from Yamaha I would really appreciate somebody's expertise on this

 

You don't need the tool to synchronise the carburettors.

 

We have the YICS chamber blanking tool available, and although many people don't use them, Yamaha recommended their use during the synchronization procedure. You can learn more about it here:

https://www.xjbikes.com/forums/threads/yikes-all-about-the-yics-system.14757

and pay particular attention to the section titled An Insight From One Who Knows......



vv7) Aftermarket YICS CHAMBER PORT BLANKING TOOL---this is the tool you'll need to perform a proper carb synchronization on any YICS motor......without it, you're just wasting time. This block-off tool is used to isolate each cylinder from the others while performing a carb synch. Updated version of the factory #90890-04068-00 tool. Some people claim that this tool is NOT needed to perform a proper synch; we disagree, and so do the Yamaha engineers who designed the YICS system. This quality tool features a snap-open and shut trunnion handle design like the original. This is NOT a cheap home-made tool and has all the proper seals, dimensions, and high-temp insulators as an original factory tool.

We recommend that you purchase a set of the HCP6380 replacement seals, too, as you'll eventually need to replace them.

HCP5460 Aftermarket YICS CHAMBER PORT BLANKING TOOL:
$

 

IMO there's no need to block the ports unless you're expecting to have the emissions checked (no U.S. states require that).

 

Yikes! I mean Yicks........another side of the story:

An Insight From One Who Knows:

To review:

According to Yamaha, the function of YICS is to promote more complete combustion at low to mid-range rpm by swirling the mixture around the combustion chamber. They never made any direct power claims -- the system was promoted as increasing mileage up to 10 percent and promoting lower emissions through a cleaner burning charge. The increase in mileage was not through leaning out the mixture -- the increase in mileage and reduction in emissions was because less throttle was required to maintain cruising speed. They could use the same cam timing, jetting, etc. (for performance) and still meet EPA regulations. Yamaha stated that the greatest effect was while cruising at 50 to 60 mph.

The swirling accomplishes two tasks: first, it assists mechanically in atomization of the fuel and second it speeds and distributes the flame front (and therefore combustion pressure wave) more evenly throughout the cylinder. The later "Genesis" (water-cooled "X" engines) design accomplished this even more effectively through the 5-valve design, which accomplishes the same task through a wider rpm range.


To blank or not to blank (during engine synch), that is the question. Ok, what is the function of synchronizing? Manufacturing tolerances and wear. Multiple carbs offer the advantage of increased power and performance over the single carb configuration for reasons beyond the scope of this discussion. But at a cost.....

As each carb is dealing with a fraction of the total air and fuel flow requirement, each carb must meter things in fractions of the total. That makes for some very tiny tolerances. In effect, we have 4 separate engines -- if one is fighting the others, then we are wasting power and fuel and are worse off than we would be with a single-carb setup! So it is crucial that each one be perfectly adjusted and that all 4 then be synchronized to work in perfect harmony.

So, how can we reliably adjust an individual carb based on the results of the adjustments, if it's companions are contributing to the results? Now, to be fair-----if the bike has been reasonably well maintained and the cylinders are all fairly close to begin with, you can usually get away without blanking the YICS passage and still achieve a reasonable state of tune. At the opposite end of the maintenance spectrum, the YICS passages are often already plugged up with many years worth of accumulated grunge and grime, so the bike is effectively being tuned with the YICS system disabled and the presence of the tool is irrelevant. But we have seen some examples of carbs where one cylinder was effectively relying on its neighbors to supply most of the mixture through the YICS system, and this most certainly affects performance, especially the top end.

Take a look for yourself:




So, my recommendation: for an engine with approximately equal compression across the cylinders and valve clearances in spec, make sure the YICS passages are clean and use the blanking tool to tune the carbs.