Jetting Guru's! Dual 3 jet Keihin CDK2 40's help! - Page 20
pxctoday

» Log in

User Name:

Password:

Not a member yet?
Register Now!

» Find OEM Parts

» Jobs

» wallpapers

Page 20 of 21 FirstFirst ... 1018192021 LastLast
Results 191 to 200 of 209
  1. #191
    Frequent Poster
    Join Date
    Feb 2008
    Location
    New Zealand
    Age
    42
    Posts
    205

    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Post #24
    Quote Originally Posted by wmazz View Post
    I have also noticed "the weird mid range hesitation with these carbs," and a it helps to modify the upper bypass holes, but
    the bottom 2 must be left alone.
    Post #108
    Quote Originally Posted by wmazz View Post
    I would recommend drilling the 2 bottom low speed bypass holes
    to .024" before installing a #78 or #80 low jet. I believe Kawasaki
    was more concerned with Hours/Gallons and exhaust emission testing
    than other manufactures. I think this is why their Keihin low speed
    bypass holes are so small.

    In 1994, the 900zxi had a low end bog that was solved by drilling
    the lower 2 bypass holes to .024" I tried jetting it richer on the low
    jets and increasing the pilot screws, but modifying the low speed
    bypass holes worked the best.

    DANGER: Only drill the bottom 2 bypass holes!
    I'm so confused, which is it?
    Sometimes the same is different, but mostly it's the same

  2. #192
    PWCToday.com Is My Home Away From Home wmazz's Avatar
    Join Date
    Jul 2013
    Location
    Riverside, CA
    Age
    62
    Posts
    3,343
    Blog Entries
    6

    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Not sure what I am quoting in post #24, but post #108 is correct.

    The greatest performance comes from enlarging the mid-range hole,
    and the 2 bottom low speed bypass holes can offer some off idle
    acceleration.

    The .024" allows for some increased acceleration off idle, without causing
    any problems with the carbs loading up at idle.

    Old Mikuni44BN carb mods for early 650 X2's would load up on the start line
    because the lower bypass holes were too big. Mikuni44BN testing showed
    that .024" worked for acceleration, without loading up. The 44SBN comes
    with .024" holes on the lower 2 bypass holes. Keihins are generally .022"

    When the lower 2 bypass holes are too large, modifications to the return line
    jet (like Novi) to reduce fuel pump pressure at idle can reduce the start line
    problems. Despite a possible fix, I don't recommend experimenting with hole
    diameters (beyond .024") unless you are prepared to accept some failures.


    Bill M.

    If people are interested, I can post BN44 carb mods that the 3 jet Keihin carb
    mods were based on. But they do not work on the 44SBN.
    Last edited by wmazz; 07-11-2022 at 04:48 PM.
    Horsepower == Speed, RPM != Speed



  3. #193
    Frequent Poster
    Join Date
    Feb 2008
    Location
    New Zealand
    Age
    42
    Posts
    205

    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Thanks for clearing that up Bill.

    I didn't end up drilling any low speed bypass holes, but I did take the mid bypass out to 1mm (I think, that was when I first tried to improve it a while ago).
    I could still never get it to run right but drilling the low jet out to 78 (from 72) and swapping from short to mid spring has fixed it. Instant response now

    I'm now at 78/50/145 with 1/2 turn on the lows and 1 turn on the highs.

    Possibly, with the bigger 145 jets, I could go leaner on the highs?
    But how much would I actually get when I'm already at 7300rpm with a bored nozzle?
    It was 7300 at 2 turns out too, so I decided to stop winding in when I wasn't seeing any gains.

    Is it normal for these 750's to have a step in the power?
    I guess it's hitting the pipe and it's hard to keep rpm between 5000 and 6000, it just wants to go!
    Sometimes the same is different, but mostly it's the same

  4. #194
    PWCToday.com Is My Home Away From Home wmazz's Avatar
    Join Date
    Jul 2013
    Location
    Riverside, CA
    Age
    62
    Posts
    3,343
    Blog Entries
    6

    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Quote Originally Posted by tigermm View Post
    I'm now at 78/50/145 with 1/2 turn on the lows and 1 turn on the highs.

    Possibly, with the bigger 145 jets, I could go leaner on the highs?
    But how much would I actually get when I'm already at 7300rpm with a bored nozzle?
    It was 7300 at 2 turns out too, so I decided to stop winding in when I wasn't seeing any gains.
    Do you ride at sea level? I'm not sure there is much to gain
    if the pilot is at 1/2. Sounds like it is running good where it
    is?

    How hot does it get there? Google says it doesn't get much
    above 24C/75F in the summer? Air Density is close to 100%

    I am curious what your set-up is, at 7300rpm, that could be good,
    or on the verge of too much rpm.


    Quote Originally Posted by tigermm View Post
    Is it normal for these 750's to have a step in the power?
    I guess it's hitting the pipe and it's hard to keep rpm between 5000 and 6000, it just wants to go!
    Common 750 porting leads to hard hitting powerbands, and
    some pipes can make it worse.


    Bill M.
    Last edited by wmazz; 07-14-2022 at 01:52 AM.
    Horsepower == Speed, RPM != Speed



  5. #195
    Frequent Poster
    Join Date
    Feb 2008
    Location
    New Zealand
    Age
    42
    Posts
    205

    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Hi Bill, yeah it doesn't get very hot here, 30C max really. The engine is standard except for having really high porting done by a previous owner. Was a couple of years ago that I pulled it apart to inspect things but the porting was way higher than anything I've seen recommended from memory. The thing that might confound any comparisons is that the whole setup is in an 8ft jetboat that I built so the intake is massively different to the ski. It'll mostly used at around sea level but occasionally may go into the highland lakes and rivers in the south island here. I guess I should expect a drop in top end at those times? If 7300 is too much then I might just put the stock nozzle back on and leave things as they are as it does seem to run well. Cheers, Mike
    Attached Images Attached Images
    Last edited by tigermm; 07-16-2022 at 04:25 AM.
    Sometimes the same is different, but mostly it's the same

  6. #196
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
    Join Date
    Jul 2008
    Location
    Chicago / Portage, MI
    Age
    40
    Posts
    3,635

    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Quote Originally Posted by theVetteman3 View Post
    With the big PJS 650 pipe and aftermarket flame arrestors, my final iteration was 78/50/132. Most of these carbs come with 72/45/135, the 145 seems real big to me. I wonder if that's because the stx was such a big ski.

    This version is the one with the main jet on the back of the plate. I believe jetting transfers over to this type. It might be worth measuring the diameter of the top of the carb, where it mounts to the flame arrestor adaptor. I know later ones shrunk down, but I thought those were still 2 jet. Bill can jump on in on if these are direct equivalents circuit wise to the early ones.

    Bumping this jetting up for others. We've still got skis going with this jetting. One day I will look into Bill's mods, but for the moment on otherwise stock 3 jet carbs from the 93-94 ss xi and xir (among others), the jetting works great.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
    2009 1100 SJ:
    Kawi 1100 build in progress
    2009 SJ MINT:
    KP steering adaptor, Worx 228 intake, PWR ride plate [47.3mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, Coffmans Sizzler [49.1mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1995 SJ MINT:
    Worx 205 intake [42.5mph gps]



  7. #197
    Frequent Poster
    Join Date
    Feb 2008
    Location
    New Zealand
    Age
    42
    Posts
    205

    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Yup the 78/50 lo/mid jetting works well.
    Mine has the 145 on the back so can confirm it works for these carbs too.

    I put the smaller (stock) nozzle on, and went slightly in on the Hi screws and now I'm hitting 7500rpm!
    Think I'm going to have to start looking for air leaks in the intake or something.
    Sometimes the same is different, but mostly it's the same

  8. #198
    PWCToday Regular
    Join Date
    Jun 2016
    Location
    redwood city, bay area, ca
    Age
    30
    Posts
    102

    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Hey I have a set of cdkii on my 550 750small pin swap and it seems like Iím not drawing fuel from the tank will really only start if I cover flame arrestors adapter with my hand

    I rebuilt the carbs a few years back with genuine keihin parts I think

    Had it running in an x2 decently but would sometimes die randomly at 1/4 throttle or less

    Ran hard on the top end after 1/4 throttle
    Anyone have this problem

    Jetting is 80/50/140 I believe right now
    Unknown pop off
    Can check

    Coffman pipe, factory water box, Ada head 180, intake transfer port siliconed, diverted exhaust manifold, sts ebox


    Sent from my iPhone using Tapatalk

  9. #199
    PWCToday.com Is My Home Away From Home wmazz's Avatar
    Join Date
    Jul 2013
    Location
    Riverside, CA
    Age
    62
    Posts
    3,343
    Blog Entries
    6

    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    You need to try the paper clip test to see if the fuel pump
    is working.

    Most likely 2 separate problems. Diagnose the starting
    first.


    Bill M.

    If it starts, it proves the fuel pump works and a more
    common problem is the likely cause.
    Attached Images Attached Images
    Attached Files Attached Files
    Last edited by wmazz; 09-12-2022 at 03:09 AM.
    Horsepower == Speed, RPM != Speed



  10. #200
    PWCToday Regular
    Join Date
    Jun 2016
    Location
    redwood city, bay area, ca
    Age
    30
    Posts
    102

    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Quote Originally Posted by wmazz View Post
    You need to try the paper clip test to see if the fuel pump
    is working.

    Most likely 2 separate problems. Diagnose the starting
    first.


    Bill M.

    If it starts, it proves the fuel pump works and a more
    common problem is the likely cause.
    Ok I will try this and will report back


    Sent from my iPhone using Tapatalk

Page 20 of 21 FirstFirst ... 1018192021 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBadvanced CMPS v4.2.0