YICS blocking tool.

Hi I am new here and live in Germany and am trying to set the carbs on a 750 and have read that I need a blocking tool. Is this really necessary? Os it possible to build one? Has anyone done this? Are there drawings or exact plans on how to build one?
I would be grateful for any help because the support for this model in Germany is zero.

 

there are drawings on this site and the internet to build one.
the general opinion here is that it is not needed


Home Made YICS Tool Diagrams

 

DIY - how to forum

Yics tool (home made) diagram and instructions

 

I've never used it, and still get a decent carb synch without it.

 

YIKES!: ALL ABOUT THE "YICS" SYSTEM.

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


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 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 it's neighbors to supply most of the mixture through the YICS system, and this most certainly affects performance, especially the top end.

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.

 

+1 on above - last paragraph says it all:

1. Valves within spec.
2. Equal compression within tolerances across the 4 cylinders
3. YICS passages are clean and free of grunge....
4. Use blanking tool when sync'ing with mamometer
5. Colortune the plugs with Gunson tool
6. Adjust idle screw as necessary

When performed properly, your bike will be dialed in.....

 

How can one know if the YICS, passages are clean ?

 

Chacal sells a cleanout tool.......to get to the holes within the passage......

 

Are you talking about the one that goes into the hole about 3/16" into the hole ? The passages are longer than that aren't they ?

 

You are correct! But the opening itself is where the "clogs" normally occur.

 

if the carbs are off you should be able to drip some gas in the intake and have it come out the end of the yics port
maybe

 

I use a rifle cleaning brush and a long cleaning rod. First the brush. Then patches soaked in carb cleaner. Replace the
patches as they get dirty. Keep running patches through till one comes out clean.

 

you still need the tool to make sure the 4 holes are free and clear of any buildup......

One can see from one end to the other for the passage to see if that is clean.......but you cant really the 4 holes at the top of the passageway...

The tool has pre-measured marks on it...so you can stick it in the passageway at the pre-measured marks and clear the holes.....

 

I can kinda understand chacal, on top of the head where the YICS o-rings are in, the head has a little indention that the o-rings protect, i can see that gas and anything else can sit and gather right at the point of entry to the cylinder.