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Thread: Carb balancing questions

  1. #1
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    Question Carb balancing questions

    hi. i did a bit of research in internet and found there are many ways to balance the carbs. among those i noticed that the vacuum gauges and fluid manometers are widely used.

    1st question - in a 4 vacuum gauge type, does it measure relative pressure to balance the carbs or does it measure the vacuum in each cylinder individually ( not relatively ) ? the reason i asked this is i can't see any relative connection in between the vacuum gauges as we see in fluid manometers. you can see the pictures below

    Name:  s-l225.jpg
Views: 73
Size:  22.9 KBCarb balancing questions-manometer.jpg

    2nd question - can we use a manometer like in the below picture, which measures two carbs at a time to balance all 4 carbs ? let's say first we balance #4 to #3 (master carb). then cap #4 balance adapter and balance #2 to #3. then cap the #3 adapter and balance #1 to #2.

    Carb balancing questions-manometer-zero.jpg

    please give some advice. thank you.

  2. #2
    Junior Biker isaacelms's Avatar
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    Hi there,
    Having done this myself I understand the questions.
    The vacumn gauges gets its reading from each individual carb. I'm pretty sure most bikes use this (especially for the output of the mc14e).

    When tuning (which has been said before) you need to balance 1 and 2 together, then 3 and 4 together and then use the middle mixture screw to balance 1 and 2 to 3 and 4. And yes 3 is the master.

    Not sure about the use of the liquid one using 2 cylinders in one tube. There is a guide to do it somewhere on here.

    I got my vacumn gauges for 100 dollars (gauge not mercury). Where are you located? I wouldn't mind you borrowing mine. I have a thread asking these questions if you want to have a look there!.

    Sent from my SM-N910F using Tapatalk
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    Quote Originally Posted by isaacelms View Post
    Hi there, Having done this myself I understand the questions. The vacumn gauges gets its reading from each individual carb. I'm pretty sure most bikes use this (especially for the output of the mc14e).When tuning (which has been said before) you need to balance 1 and 2 together, then 3 and 4 together and then use the middle mixture screw to balance 1 and 2 to 3 and 4. And yes 3 is the master.Not sure about the use of the liquid one using 2 cylinders in one tube. There is a guide to do it somewhere on here.I got my vacumn gauges for 100 dollars (gauge not mercury). Where are you located? I wouldn't mind you borrowing mine. I have a thread asking these questions if you want to have a look there!.Sent from my SM-N910F using Tapatalk
    thank you very much for your quick reply and kindness. i already made that liquid one since it's easy to make. but it measures the relative vacuum pressure to balance the carbs since all 4 tubes are connected to each other. just wondering which manometer is accurate. the liquid one or the vacuum dial gauges ?

    my idea is this. since the vacuum gauge measures the vacuum pressure in each carb individually, it should be ok to use tube manometer which measures two carbs at a time ( below picture ) to match other 3 carbs vacuum to the master carb vacuum.
    this is what i did. first we matched #4 to master. then we closed the #4 balance adapter hole and matched #2 to master. after that we closed the balance adapter hole in master and matched #1 to #2. ( same procedure we do in the bench sync )

    Carb balancing questions-3929d1491218677-carb-balancing-questions-manometer-zero.jpg

    honestly i tried above method. it worked well and bike ran pretty well. as i said above i matched all 3 carbs to the master carb ( #3) so all 4 carbs should have the same vacuum pressure if we measure them individually. but as a test i measured #1 and #4 carbs and they were a bit out. not much but they didn't seem to have the same vacuum pressure. just wondering the cause. thank you.
    Last edited by Bikeboom; 3rd April 2017 at 07:06 AM.

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  5. #4
    Junior Biker isaacelms's Avatar
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    Okay! That sounds cool, I don't really know much more on it. I'm sure someone will chime in.

    I think I read a while back that if your balance is too out then it can suck the liquid into the engine.

    My vacumn ones where pretty accurate, and I'm sure the liquid one can be pretty close. So long as you will be able to ensure the vacumn is the same!

    And it's cool that you have done it before. And sometimes they will be a bit different as the engine wears.

    I have recently run into an issue after doing my valve clearances with the idle not dropping below 2k without stalling. I think it is with the supercheap carb cleaner (that I'm pretty sure is just paint stripper, as I used to wash ink off myself when I worked at a screen print place haha)



    Sent from my SM-N910F using Tapatalk
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  6. #5
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    Quote Originally Posted by isaacelms View Post
    Okay! That sounds cool, I don't really know much more on it. I'm sure someone will chime in.
    I think I read a while back that if your balance is too out then it can suck the liquid into the engine.
    My vacumn ones where pretty accurate, and I'm sure the liquid one can be pretty close. So long as you will be able to ensure the vacumn is the same!
    And it's cool that you have done it before. And sometimes they will be a bit different as the engine wears.
    I have recently run into an issue after doing my valve clearances with the idle not dropping below 2k without stalling. I think it is with the supercheap carb cleaner (that I'm pretty sure is just paint stripper, as I used to wash ink off myself when I worked at a screen print place haha)
    Sent from my SM-N910F using Tapatalk
    thank you very much for your information. to make it more clear i've attached my carb below.
    Carb balancing questions-snjbr5.jpg

    since i had bench synced it before this is how it worked. my master carb is #3. balance screw "c" adjusts only the carb #4. balance screw "b" adjusts only the carb #2 and balance screw "a" adjusts only carb #1.
    so this is what i did. i made a manometer which measures two carbs at a time. first i matched $4 to #3 then i matched #2 to #3 after that i matched #1 to #2 ( since #2 already matched to our master carb #3 ).
    so practically above procedure worked fine. but when i selected a random pair like #1 and #4 and checked them using the same manometer, they were bit out. that's what bothers me now if you can give me some advice it would me much appreciated, thank you.

  7. #6
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    bit of a tip. rather than setting up the carbs as junk and then try to balance them. whilst on the bench, get a bit of fuse wire and get the gaps between the butterfly and throat the same across the board. then balance form there. when we did this, the balance was almost spot on. so much so we didn't bother making it perfect. takes the PITA bits of getting the thing running like rubbish then winding up/down throttle constantly.
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  8. #7
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    Quote Originally Posted by Slipry View Post
    bit of a tip. rather than setting up the carbs as junk and then try to balance them. whilst on the bench, get a bit of fuse wire and get the gaps between the butterfly and throat the same across the board. then balance form there. when we did this, the balance was almost spot on. so much so we didn't bother making it perfect. takes the PITA bits of getting the thing running like rubbish then winding up/down throttle constantly.
    yea you are right i've already done the bench sync & it worked very well. i used printing paper strips to do that. just doing this manometer thing to make it a bit more accurate thank you very much.
    Last edited by Bikeboom; 3rd April 2017 at 09:23 PM.

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