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YICS

Discussion in 'XJ Technical Chat' started by JeDaC, Jul 11, 2009.

  1. JeDaC

    JeDaC New Member

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    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?
     
  2. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    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.
     
  3. JeDaC

    JeDaC New Member

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    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?
     
  4. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    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.
     
  5. Polock

    Polock Well-Known Member

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    i'am sorry sir but that defies my logic
     
  6. Robert

    Robert Active Member

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    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.
     
  7. skeeter

    skeeter Member

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    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?
     
  8. wizard

    wizard Active Member

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

    SQLGuy Well-Known Member

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    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
     
  10. wizard

    wizard Active Member

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

    Robert Active Member

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    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.
     
  12. JeDaC

    JeDaC New Member

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    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?
     
  13. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    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.
     
  14. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    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.
     
  15. Polock

    Polock Well-Known Member

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    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
     
  16. Polock

    Polock Well-Known Member

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    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"
     
  17. SQLGuy

    SQLGuy Well-Known Member

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    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

    ?
     
  18. Polock

    Polock Well-Known Member

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    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
     
  19. SQLGuy

    SQLGuy Well-Known Member

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    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.
     
  20. Polock

    Polock Well-Known Member

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    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.
     

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