Jetting Guru's! Dual 3 jet Keihin CDK2 40's help! - Page 15
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  1. #141
    PWCToday.com Is My Home Away From Home WFO Speedracer's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    My greatest fear is that all these vacuum leaks will suck all the oxygen out of the atmosphere and we will be left gasping for air barely clinging to life, I mean if it is really true that all Jet skis have multiple vacuum leaks we are all doomed !
    Y'all know me, still the same O.G. but I been low-key
    hated on by most these &^$$@s with no cheese, no deals and no G's, no wheels and no keys, no boats, no snowmobiles, and no skis, mad at me cause I can finally afford to provide my family with groceries

    I was 300SXing when 300SXing wasn't cool !

  2. #142
    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 mcn6 View Post
    You agree with B.S. Bill that a single 44 SBN performs "mediocre" compared to a single Keihin on similarly modified intake assemblies? How about dual Keihin's against dual BN40/38 I-bodies in similar applications?

    I like Keihin's on stock boats and actually prefer Keihin PWK Air Strikers on my Banshee builds. However, tuning parts are numerous, cheap and readily available for PWK's which is definitely not the case with Keihin CDK's. Personally, I prefer to just order whatever jets, springs, N/S needed and be done with it as opposed to investing the time and effort to back door tune a Keihin's. But that's just me, if you have made the effort to come up with something that works I commend you as there are a bunch of stock Keihin racks off of 1995 and 1996 750's out there collecting dust. However, to state that the performance of a properly tuned Mikuni is mediocre to a comparable Keihin is total B.S. evidenced by any starting line at any race anywhere.
    Ahh as I understood from what Bill quoted, we were talking a single 44-46 sbn vs dual 40 3 jet Keihins. Yes I understand Mikunis are a better carb. But if I was on the line for a race, I'd rather have twin 40mm 3 jet Keihins, than a single 44 or 46 sbn. That was my point.

    I see now Bill was talking about the design being better too. I can't comment on that. But given my own skis the 3 jet Keihins when set up well performance is close enough to 38mm Mikunis that I personally would be hard pressed to tell the difference. For my own preferences of speed and overall power / torque and throttle response, both have clear advantages over single carbs.

    Also of note, with the jetting I have indicated, no internal modifications were necessary. And although needle and seats for these CDK2s can be hard to find, jets are easy. For the total money invested, on recreational skis they do have their place.
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  3. #143
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Quote Originally Posted by JonnyX2 View Post
    If your high and low screws exceed two turns JET UP one size, and retest. Most carb tuning specs do not exceed 1.5 turns out.
    So don't change the pop off but instead increase the Jets? Like i said before I'm at 135 main 55 mid and 78 low and 1.75 low screw and 1.5 high screw

  4. #144
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    That's what I was saying. There are a bunch of take offs from 95-96 twin carb 750's out there... If you have developed something for them that works and could be easily tuned for varying parameters like elevation and rider weight you deserve a medal, imho!

    btw, where are you purchasing jets and springs for your CDKII carbs?

    Quote Originally Posted by theVetteman3 View Post
    Ahh as I understood from what Bill quoted, we were talking a single 44-46 sbn vs dual 40 3 jet Keihins. Yes I understand Mikunis are a better carb. But if I was on the line for a race, I'd rather have twin 40mm 3 jet Keihins, than a single 44 or 46 sbn. That was my point.

    I see now Bill was talking about the design being better too. I can't comment on that. But given my own skis the 3 jet Keihins when set up well performance is close enough to 38mm Mikunis that I personally would be hard pressed to tell the difference. For my own preferences of speed and overall power / torque and throttle response, both have clear advantages over single carbs.

    Also of note, with the jetting I have indicated, no internal modifications were necessary. And although needle and seats for these CDK2s can be hard to find, jets are easy. For the total money invested, on recreational skis they do have their place.



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  5. #145
    Top Dog bandit88's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Chris, I order mine from JetsRUs. https://www.jetsrus.com/carburetor/c...iew_parts.html
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  6. #146
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    I think what Mr. X-2 is saying refers to the high speed jet (main jet) only, usually best to have high speed needle between .75 and 1.25 turns out. Basically, use your high speed needle setting to tell you which way to go with your main jet. You would typically change pop off pressure and/or pilot (low speed) jet only if you have a rich or lean condition coming off idle.

    Read pages 13-17 here: http://www.mikuni.com/pdf/sbn_manual.pdf It is for Mikuni carburetors, but most of the carb tuning information is applicable to Keihin also.

    Also, verify that your internal filter screen is not clogged, bypass your fuel selector switch and ditch your in-line fuel filter. If your internal filter is clogged or you have a need for an in-line fuel filter you need to clean you gas tank and find a better place to purchase your gas.

    Quote Originally Posted by Jdbarnes89 View Post
    So don't change the pop off but instead increase the Jets? Like i said before I'm at 135 main 55 mid and 78 low and 1.75 low screw and 1.5 high screw



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  7. #147
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Oh its true alright! I have been collecting old scuba tanks and variable pitch impellers for a while now...

    Quote Originally Posted by WFO Speedracer View Post
    My greatest fear is that all these vacuum leaks will suck all the oxygen out of the atmosphere and we will be left gasping for air barely clinging to life, I mean if it is really true that all Jet skis have multiple vacuum leaks we are all doomed !



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  8. #148
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Mucho Garcias bandit. Main jets: https://www.jetsrus.com/a_jets_by_ca...4-36_main.html
    Pilot jets: https://www.jetsrus.com/a_jets_by_ca...4-35_slow.html

    I only see two different weight pop off springs, is that all there is or do you have a source for pop off springs? How about jet blocks??

    Quote Originally Posted by bandit88 View Post



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  9. #149
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    Well can't say for sure until i water test..... But i think i figured out the issue..... I almost don't want to admit my mistake lol, but i got to looking at a diagram of these cdk2 and realized i had put the gasket on the invites side of the diaphragm...... �� Needless to say it runs a bit better on a hose at 1 turn out each but we shall see what happens with a load on it I'll report back but thank you all for the info!!!! Even if i made a dummy move assembling them lol I'll see what happens with the 135, 55, 78 jetting and go from there!!!

  10. #150
    Resident Guru RenoJetTech's Avatar
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    Re: Jetting Guru's! Dual 3 jet Keihin CDK2 40's help!

    And that's a Cdk, try looking at the assembling of a BN carb, almost like watch repair.
    Lots of looks at this post.
    I like the increments.
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