Jetting Guru's! Dual 3 jet Keihin CDK2 40's help! - Page 11
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  1. #101
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Well currently I'm doing a rebuild due to the sleeve cracking on port Bridges, then somehow loosening up in the jug and then dropping down, waiting on a new cylinder to arrive then get bored and matched to my Pistons, i have a weird issue on it though, when i shut the engine down it wants to keep chugging along with these dual carbs, if i put my single 38 keihin on, everything works just fine, but it just doesn't seem nearly as responsive with that carb...
    Almost thinking about setting the dual 40s aside.......

  2. #102
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Quote Originally Posted by theVetteman3 View Post
    Duals are great if you want fuel economy or don't like copying one carb setting to another.
    Meant singles here.. obviously. Lol.
    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 [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1998 SXI PRO:
    3DR hull mods [TBD]



  3. #103
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Quote Originally Posted by Jdbarnes89 View Post
    Well currently I'm doing a rebuild due to the sleeve cracking on port Bridges, then somehow loosening up in the jug and then dropping down, waiting on a new cylinder to arrive then get bored and matched to my Pistons, i have a weird issue on it though, when i shut the engine down it wants to keep chugging along with these dual carbs, if i put my single 38 keihin on, everything works just fine, but it just doesn't seem nearly as responsive with that carb...
    Almost thinking about setting the dual 40s aside.......
    Wow crazy. That sounds like an air leak. Any time an engine is doing something you didn't pull the throttle for, suspect an air leak. I had a 750 that was vaguely similar and it had a massive crack in the intake manifold and could not hold air at all. If you haven't done it, i would do a leakdown test thru the bottom end right up to the carb base. Make a thick rubber gasket that you can clamp between the manifold and carbs. It should be air tight to 8-10 psi for at least 10 min no drop in pressure. On some of my engines I leave them for an hour just to see. There are threads on here with how to do leakdown tests if you havent done it before. I do it on all my new built engines. Use Threebond 1211 on all surfaces as you build the engine and report back.
    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 [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1998 SXI PRO:
    3DR hull mods [TBD]



  4. #104
    Top Dog Benflynn's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Just a reminder, all the 3 jet carbs sent the same, they have diff locations of the 3rd jet, and have diff transfer homes at the base, so for Juliette g recommendations you have to be sure all is the same

  5. #105
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    I think what i might be experiencing is pre ignition I've been using 91 octane non oxy fuel.... I put things together just to test compression and it was at 185psi and just like diesel fuel, gas will ignite if it's compressed enough, but I'll check into the leak down stuff also
    Last edited by Jdbarnes89; 05-03-2019 at 02:50 PM.

  6. #106
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Quote Originally Posted by Benflynn View Post
    Just a reminder, all the 3 jet carbs sent the same, they have diff locations of the 3rd jet, and have diff transfer homes at the base, so for Juliette g recommendations you have to be sure all is the same
    This is a good point. If I didn't mention it, I should have. My settings apply only to the 3 jet 40mm Keihin CDK2s which came on the 94 ss xi and xir small pin dual carb 750. Maybe some 95 ss xi skis as well, not sure. They came on all lime green head engines but I am not sure if they were exclusive to those. All three jets should be on the same side. This isn't an issue because these are very plentiful.

    Regarding other small pin 40mm options I believe there is at least one, with one jet on the back of the plate the jets thread into. I can't speak to those but i believe they should function the same jetting wise. If you have the smaller 38mm big pin ones, which if I recall correctly also had the jets on different sides, throw them in the trash and get mikunis and manifold off the later big pins 750 pro and sxr.
    Last edited by theVetteman3; 05-04-2019 at 09:52 AM.
    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 [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1998 SXI PRO:
    3DR hull mods [TBD]



  7. #107
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    So are there issues with air leaks at the throttle plates? On these 40s? I'm not sure what to call it, but rod that goes side to side that holds them? Do they get worn out?

  8. #108
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Quote Originally Posted by Jdbarnes89 View Post
    So are there issues with air leaks at the throttle plates? On these 40s?
    Not really, although all carbs are capable of leaking there.
    The worst carbs for leaking throttle shafts were early snowmobile
    and watercraft cabs like Walbro, Mikuni, Keihin, Tillitson round
    body carbs. The early Mikuni Super BN's were also a problem.

    On all of these carbs, worn out throttle butterflys at each side
    of the throttle shaft, and side to side slop on the throttle shaft
    were a signs of a problem.

    Another source for vacuum leaks occur after you disassemble the
    carb rack. If the carb rack is reassembled without using the intake
    manifold as a jig. It is very likely that a new leak at the carb base
    gaskets will occur.


    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!


    Quote Originally Posted by Jdbarnes89 View Post
    then somehow loosening up in the jug and then dropping down
    Sleeves dropping on small pin cylinders used to be a common
    cause for engine failures

    Quote Originally Posted by Jdbarnes89 View Post
    I think what i might be experiencing is pre ignition I've been using 91 octane non oxy fuel....
    I put things together just to test compression and it was at 185psi and just like diesel fuel, gas will ignite if it's compressed
    enough, but I'll check into the leak down stuff also
    How do you know it has 185psi? Most compression gauges read low.


    Bill M.

    Any pictures of your old pistons?
    Last edited by wmazz; 05-05-2019 at 04:36 AM.
    Horsepower == Speed, RPM != Speed



  9. #109
    PWCToday.com Is My Home Away From Home JHR's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    following .

  10. #110
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Well i tested compression with 3 testers mine is 30psi low but the other two were the same, the engine almost seems to fire with the kill switch off, I'm dropping the core cylinders to be bored of at the local engine guy tomorrow1557098362971736113609717786606.jpg

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