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YACS Blanking

Discussion in 'XJ Technical Chat' started by paul.hardy, Jul 9, 2012.

  1. paul.hardy

    paul.hardy Member

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    I have just got back into bikes after not having one for years having cut my teeth on old Kwaka 900 and Honda 750 4s I recently came across this old 83 XJ750R. which has been great fun to ride. It had an oil leak around the front of the head casket so I took the opotunity to pull of the head and check out the condition of the motor top end. Anyway it all looked pretty good in the bore etc. A bit of scoring on the cam bearings but beaning 30+ old it is pretty good. So after I put it back together again I sat there contemplating ballencing the carbs at some stage and wondered what would be the outcome if I had of blanked of the YACS holes which would not have been hard to do with the head off. Then I would not need a blanking tool. How much would it actually affect the bike performance and economy ?
     
    paul.hardy, Jul 9, 2012
    #1
  2. Orange-n-Black

    Orange-n-Black Well-Known Member

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    Welcome to the site. The YICS ports have to be blocked when snycing the carbs. There is a special tool for this or you can make your own. You can access the YICS by removing the horizontal bolts on the sides of head towards the back of the motor and just below the head intake boots. Of coarse a valve check is in order before syncing.
    As for permanently blocking the YICS and how it would affect performance, I'm not sure. I think it would depend on what air, carb and exhaust setup you have in mind. Pod filters are difficult to tune right on these bikes because of the CV carbs and I think the YICS also adds to the frustrations.
     
    Orange-n-Black, Jul 9, 2012
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  3. biggs500

    biggs500 Active Member

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    biggs500, Jul 9, 2012
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  4. mlew

    mlew Well-Known Member

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    I blocked mine on the XJ11 when I had the head off to fix a valve problem. Glad i did it. No more YICS tool needed and it runs the same. I have not noticed any difference if power or fuel economy.
    If the YICS system was something great they would still be using it today.
     
    mlew, Jul 9, 2012
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