1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Help Kawasaki ninja ZXR250c carb problem and vaccum valve

Discussion in 'Kawasaki 250cc In-line 4's' started by shahzeb, Mar 7, 2016.

  1. shahzeb

    shahzeb Member

    Messages:
    15
    Likes Received:
    3
    Trophy Points:
    13
    Joined:
    Mar 7, 2016
    Gender:
    Male
    Location:
    Pakistan
    My Bike:
    Kawasaki ninja zxr250
    Hello everyone, its my first thread on this forumn, and believe me i am really happy that i've found a forum where people are discussing about the "zxr 250"
    I have a set of question upon which i need your expert advices. I recently bought this bike and its causing me a lot of trouble with the carbs.
    Question#1:
    Can someone please tell me what does the vaccum valve do and its importance.
    [​IMG]
    Question#2:
    In my bike hose#23 is connected directly to hose#6 is this correct ?
    [​IMG]
    Question#3:
    supposedly this vacuum valve is not important and i plan on removing it, how should it be removed ? Please see the picture and tell if this procedure is correct or not.
    [​IMG]
    Question#4:
    While riding the bike there is a very big surge/misfire/sputtering exactly between 4-6k rpm. If i am able to pass the 6k range than the bike accelerates like a dream but between 4-6k rpm its a disaster. Maybe this is because my above hoses are not connected correctly ? or is there a problem in jet needle ?

    Really looking forward to your expert advices and i pray that i am able to solve these problems. Thanks in advance. I am attaching a blank picture so if any wants to circle them out to explain. Here it is:
    [​IMG]
     
    • Like Like x 1
  2. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

    Messages:
    8,018
    Likes Received:
    5,877
    Trophy Points:
    1,168
    Joined:
    Aug 7, 2010
    Gender:
    Male
    Location:
    Brisbane
    Home Page:
    My Bike:
    90 CBR250RR ,Suzuki T500, 2005 GSF1200 Bandit and a 1972 t250j
    I experienced stuttering between 4k and 6k on my ZXR, it turned out I had some carb seals that failed, the are no longer available from Kawasaki, but the good news there is a ccompany in Thailand called Litetek who do kits for them - see http://litetek.co/Carb_Kit_Kawasaki_ZXR250.html The seals in question are shown below in red.

    Cheers
    Chris


    zxr250c.png
     
    • Like Like x 1
  3. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

    Messages:
    3,296
    Likes Received:
    2,301
    Trophy Points:
    923
    Joined:
    Dec 23, 2012
    Gender:
    Male
    Location:
    Thailand
    Home Page:
    My Bike:
    Yamaha FZR400 3TJ1, Honda MC22
    Hello, and welcome to the forum. is that a manual for a ZXR250 @shahzeb?
     
  4. shahzeb

    shahzeb Member

    Messages:
    15
    Likes Received:
    3
    Trophy Points:
    13
    Joined:
    Mar 7, 2016
    Gender:
    Male
    Location:
    Pakistan
    My Bike:
    Kawasaki ninja zxr250
    Thank you for replying, I see these are the o-rings/seals for the fuel T- joint ? I wonder how it effects the bike other than providing a leak free from fuel. But, I'll look into it and try replacing them.
     
  5. shahzeb

    shahzeb Member

    Messages:
    15
    Likes Received:
    3
    Trophy Points:
    13
    Joined:
    Mar 7, 2016
    Gender:
    Male
    Location:
    Pakistan
    My Bike:
    Kawasaki ninja zxr250
    Hello, thank you for the greetings :), yes it is the manual for zxr250c.
     
  6. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

    Messages:
    8,359
    Likes Received:
    4,917
    Trophy Points:
    1,168
    Joined:
    Jun 14, 2012
    Gender:
    Male
    Occupation:
    Troublemaker
    Location:
    North by NW NSW Oztralia - Tamworth
    My Bike:
    *Kawasaki ZXR250C *Yamaha FZR250R 3LN1 *Suzuki GSX250 *Triumph Bonneville 750 T140V
    Vacuum valve ..... fuel tap runs on vacuum as there is no fuel pump and vacuum assists the carbs to operate

    Question 2 ... yes

    Overhaul the carbys and set up the vacuum hoses as per the schematics ..... the little Japanese men in white coats knew what they were doing when they built the bike originally.

    Check your RR also as they are prone to overheating and burnt plugs on the C model ... #11 in your diagram
     
    • Like Like x 2
  7. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

    Messages:
    8,018
    Likes Received:
    5,877
    Trophy Points:
    1,168
    Joined:
    Aug 7, 2010
    Gender:
    Male
    Location:
    Brisbane
    Home Page:
    My Bike:
    90 CBR250RR ,Suzuki T500, 2005 GSF1200 Bandit and a 1972 t250j
    Yep, please do not remove the vacuum, it will make things worse. These seals fail alot and let air into the system, the LiteTek kit fixes it, its well worth doing, its a much different bike when the issue is resolved. The other cool thing is the LiteTek kit has the seals that go between the airbox and the carbs which are almost always missing.

    Good luck, keep us in the loop as to how you go.
     
    • Like Like x 2
  8. shahzeb

    shahzeb Member

    Messages:
    15
    Likes Received:
    3
    Trophy Points:
    13
    Joined:
    Mar 7, 2016
    Gender:
    Male
    Location:
    Pakistan
    My Bike:
    Kawasaki ninja zxr250
    Thanks for the reply :), will defenitely overhaul the carbs.
     
  9. shahzeb

    shahzeb Member

    Messages:
    15
    Likes Received:
    3
    Trophy Points:
    13
    Joined:
    Mar 7, 2016
    Gender:
    Male
    Location:
    Pakistan
    My Bike:
    Kawasaki ninja zxr250
    Will surely try the LiteTek kit, i hope the guy can ship it to my destination. I also plan on trying to shim the jet needles to see if i am able to solve the surge.
     
  10. shahzeb

    shahzeb Member

    Messages:
    15
    Likes Received:
    3
    Trophy Points:
    13
    Joined:
    Mar 7, 2016
    Gender:
    Male
    Location:
    Pakistan
    My Bike:
    Kawasaki ninja zxr250
    Alright guys, i need to drop a big bomb on u guys. After inspection i have found out that i have a C model body and a A model engine. I've searched and found that the A model didnt had a vaccum valve. Now i am totally lost. The carbs are from the C body aswell as they have jets 122 and 125 while the A model had 125 and 128. The cdi is from the C model aswell, while searching on this forum i found that the cdi works on both model, but someone please confirm this. Now the big question, should i setup the bike according to the C model or according to the A model ? Should i keep the vaccum valve or remove it ? Need your help guys.
     
  11. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

    Messages:
    2,140
    Likes Received:
    1,168
    Trophy Points:
    823
    Joined:
    Nov 19, 2013
    Gender:
    Male
    Location:
    Melbourne
    My Bike:
    Spada & VT250F
    Hello Shahzeb,

    The A model also has a Vacuum Fuel tap. Your carb boots should have a small metal tube sticking out of them. This is the tube you use when you're balancing your carbs. You can also use these tubes to create a vacuum to open the fuel tap and let fuel flow into the carbs. I know Kiffsta said not to remove the Vacuum Valve from your engine, but I feel you can as long as you understand what the C model Vacuum Valve actually does ... opens the fuel tap when the engine is turning over and generating a vacuum. From memory, the C model Vacuum Valve uses the same carb boot tubes, so up to you if you want to keep it or toss it. Old saying "if it's not broken, don't fix it!".

    FYI, I run a C engine in an A frame and the carb main jets are for A spec (125;128;128;125) I have run the carbs/engine with and without a Vacuum Valve with no difference.
     
    • Like Like x 2
  12. shahzeb

    shahzeb Member

    Messages:
    15
    Likes Received:
    3
    Trophy Points:
    13
    Joined:
    Mar 7, 2016
    Gender:
    Male
    Location:
    Pakistan
    My Bike:
    Kawasaki ninja zxr250
    Alright guys, recent update,
    Synced the carbs today, the bike is idling very well but the low end performance is becoming even worse. In the range of 3k-6k performance is very poor it stutters, make a wierd misfiring like the engine is going to stall but if i am able to pass the 6k range it accelerates pretty well.
    One more thing to add when i start the bike the idles remain at 2k for 3seconds than drops to 1.5k. The pilot screws are at 2.5 turns out.

    -I am using the vaccum valve and it is plugged as the manual says.
    - I am Pretty sure the cdi of the C model is working well with the A model engine, otherwise there would have been misfires even in revving it in neutral ? In neutral it revs smoothly without any misfires or stuttering.
    - Any advice on shimming the jet needles ?

    Just ordered complete rebuild kit from motorcycle spares warehouse. waiting for it to arrive.
    @Frankster any more valuable advice u would like to add ? do u have any knowledge about the interchangeability of the A and C model CDI ?
     
  13. shahzeb

    shahzeb Member

    Messages:
    15
    Likes Received:
    3
    Trophy Points:
    13
    Joined:
    Mar 7, 2016
    Gender:
    Male
    Location:
    Pakistan
    My Bike:
    Kawasaki ninja zxr250
    P.S any difference in the flywheel/pickup of the A and C model ????
     
  14. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

    Messages:
    2,140
    Likes Received:
    1,168
    Trophy Points:
    823
    Joined:
    Nov 19, 2013
    Gender:
    Male
    Location:
    Melbourne
    My Bike:
    Spada & VT250F
    A & C model CDI should be basically the same. Many ZXR riders swap them. The C has an extra wire for the kick stand cut off and I think the C also has an auto Head light built in...I think the A CDI doesn't automatically turn on the headlight. The A & C engine blocks are the same (hence why they can be used between the 2 models). The main difference is bore and stroke and, as you've discovered, carbs jets and Vacuum Valve. Pickups and all other internals should be the same. Both Kiffsta and I believe the A engine and carbs is the better of the two. The hesitation you're experiencing is something Kiffsta has experienced in one of this bikes. From memory, something to do with fuel inlet to carbs, but @kiffsta can confirm for you. Cheers
     
  15. DougFella

    DougFella Well-Known Member Premium Member Contributing Member

    Messages:
    203
    Likes Received:
    158
    Trophy Points:
    248
    Joined:
    Mar 2, 2013
    Location:
    South-east QLD
    My Bike:
    1989 ZXR250a, 2007 Triumph Sprint St 1050
    I had a A model frame with the C model engine and A model CDI. Don't know if how it works in reverse but I spend almost 2 years trying to get them to work. I replaced pretty much my entire bike and talked to every electrical expert I could find, never sorted the problem. I finally bit the bullet and put the correct engine in the frame and it worked perfectly straight away.

    I can't remember exactly but when I was looking at the C model CDI wiring diagram and comparing it to the A model one I remember being annoyed because something was in a different position that meant it was not going to be a simple switch out of the CDI's. If someone knows an actual rider that has just switched out the CDI's from model to model I'd like to know.

    On the A model the pipe that runs to the vacuum valve on the C model just runs into the air box on the A model. Your C model carbs will work perfectly fine on the A model engine you may want to make the adjustments though to suit.
     
    • Like Like x 2
  16. DougFella

    DougFella Well-Known Member Premium Member Contributing Member

    Messages:
    203
    Likes Received:
    158
    Trophy Points:
    248
    Joined:
    Mar 2, 2013
    Location:
    South-east QLD
    My Bike:
    1989 ZXR250a, 2007 Triumph Sprint St 1050
    For visual reference:

    Manual.PNG

    I've never understood why they need the vacuum valve on the C model so be interested to know more too. 8 goes to "air cleaner hose" 7 vents to atmosphere. Don't own a C model but I assume when it says air cleaner hose it mean it runs to the airbox. Someone with a C model could clarify. It must do however because the way the black magic inside the carbs works I think it gets some of the air pressure from the air box's pressure and uses that in the carbs. Again, black magic, someone who knows more will clarify.

    This is what it looks like on my A model

    20160107_110415.jpg
     
    Last edited: Mar 9, 2016
  17. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

    Messages:
    2,140
    Likes Received:
    1,168
    Trophy Points:
    823
    Joined:
    Nov 19, 2013
    Gender:
    Male
    Location:
    Melbourne
    My Bike:
    Spada & VT250F
    Actually, Doug might be right. To be 100% honest, I can't actually remember without having a look at the bike tonight, but I'm pretty sure I have a C CDI running on my setup. I swapped the entire loom from a C model to make sure it was all okay. So to clarify, I am running a C engine in an A frame with a C CDI and Loom. My carbs are from an A engine and have the A jetting (125;128;128;125). I am running my C engine WITHOUT a Vacuum Valve.
     
    • Like Like x 1
  18. shahzeb

    shahzeb Member

    Messages:
    15
    Likes Received:
    3
    Trophy Points:
    13
    Joined:
    Mar 7, 2016
    Gender:
    Male
    Location:
    Pakistan
    My Bike:
    Kawasaki ninja zxr250
    First of all thank u for the detailed reply.
    Now the cdi concerns me, I am using A engine with C cdi. Do u have the wring of A model? If u have than please send it to me on sk_durani@hotmail.com, i'll give it a look and compare. Can u please tell me what problems where u facing with the interchanged cdi's? Did u try swapping the flywheel/trigger with one another ???
     
  19. shahzeb

    shahzeb Member

    Messages:
    15
    Likes Received:
    3
    Trophy Points:
    13
    Joined:
    Mar 7, 2016
    Gender:
    Male
    Location:
    Pakistan
    My Bike:
    Kawasaki ninja zxr250
    Can a timing light help in confirming the timing ???? on idle the timing light should be on 1/4 mark when cylinder 1 or 4 is connected and on 2/3 mark when 2 or 3 is connected ??? and it should advance to F mark on say 3k or 4k rpm ???? As far as i remember the flywheel has 1/4 and 2/3 marks does it have the F (forward mark) ???
     
  20. shahzeb

    shahzeb Member

    Messages:
    15
    Likes Received:
    3
    Trophy Points:
    13
    Joined:
    Mar 7, 2016
    Gender:
    Male
    Location:
    Pakistan
    My Bike:
    Kawasaki ninja zxr250
    @DougFella @Frankster Can anyone of u please tell me the part no of the A and C model CDI ??? as far as i remember the C model cdi has a large B written on it ??? A sure part no of A model CDI will really help me in my search. I'll go for a hunt for the A model CDI, but first i need to compare the wiring diagrams of A and C model.
     

Share This Page