pxctoday

» Log in

User Name:

Password:

Not a member yet?
Register Now!

» Find OEM Parts

» Jobs

» wallpapers

Page 2 of 5 FirstFirst 1234 ... LastLast
Results 11 to 20 of 44
  1. #11
    PWCToday.com Is My Home Away From Home wmazz's Avatar
    Join Date
    Jul 2013
    Location
    Riverside, CA
    Age
    57
    Posts
    2,339
    Blog Entries
    6

    Re: Keihin CDK 2 - Reverse Jetting?

    This is somewhat of a duplication of the above post. But the post I am quoting from
    demonstrates that a problem of some kind must exist. The dual carbs should have been
    a simple installation.

    Quote Originally Posted by Miguelxj View Post
    Recomended popoff for these carbs range from 10 to 24 psi. With higher popoffs the engine
    would run lean on low rpms, had to pinch it.
    There is no published Kawasaki pop-off recommendations that I am aware of. Only Polaris
    and the blue 42mm carb (SUDCO). I am certain the pop-off that works with the stock jetting
    is at least 26 to 30psi.

    If the engine was running lean with the stock pop-off and jetting, the real question is
    why? was the engine running lean.


    Bill M.

    A vacuum leak on the reed gaskets is a common cause for a problem
    that exists after an intake manifold switch. BM
    Last edited by wmazz; 08-20-2016 at 10:10 PM.
    Horsepower == Speed, RPM != Speed



  2. #12
    Frequent Poster Miguelxj's Avatar
    Join Date
    Jul 2014
    Location
    Portugal
    Age
    36
    Posts
    160

    Re: Keihin CDK 2 - Reverse Jetting?

    Quote Originally Posted by wmazz View Post
    You can not reverse jet a set of Keihins, But you have one of the better sets of
    Keihin cabs. Drilling the small hole under the mid-range check valve to 1mm will
    give you excellent throttle response. Better than many Mikuni's.

    James (WaterHappy) has a pair of Keihin's from a Polaris 1050 on his 800cc PJS
    Super Cylinder engine, and they have many advantages over a set of Mikuni's.
    His set has (2) 1mm holes.




    First off, what is the reason or problem that led you to such rich jetting.

    What was the original problem?
    What is the low speed (pilot) screws turned out too?
    ""Important"" What impeller and nozzle are you using?
    Is the Coffman pipe dried out?

    The stock flame arrestor is very free flowing, and there is no reason to
    lower the pop-off when you made the change.

    What type of gaskets are you using on the carb base? and have you
    recently rebuilt the carbs?


    Bill M.
    Hi Bill thanks for taking the time to read this!


    Both the engine and carbs were fully rebuilt and I think its important to say I didn't have a running platform to start with (not good if you're doing this kind of work for the first time.... :P)

    So the engine's donor ski was bought not running (it fired but the carbs were out of whack) but it came with a like-new set of new carbs to replace the old ones. The owner didnt have much experience and never new what was wrong with it. As I parted it out, I realized the carbs were missing the low speed screws................ I got these from the old set of carbs that although looked very "used", the screws were in perfect condition. I am now regretting not spending the extra cash and buying a good quality gasket kit, as the one I got from eBay had a "cheap-o" plastic material for the check-valves.


    Current LS has 2 turns out and HS 2,5 turns out. It seems a bit too much so I tried some bigger jetting and no luck. I had to turn them out basically the same amount of turns.

    Currently with stock X2 nozzle and 15/18 skat-trak. Tried it first with a 15.5" solas. The 15/18 doesnt seem like its strugling as the RPMs get to aprox. 6.5K, just as the 15.5" was reaching...?

    Coffman pipe is setup as (I think) it should: pipe going from cyl.head to front of head pipe and then the pipe from the rear of head-pipe is routed to the stock XI temp sensor, with a "T" diverting water to the stinger.

    Gaskets on the carbs base are stock gaskets that came with a kit I bought in the UK. Seemed good quality but its true I have removed and installed the carbs about 5 or 6 times now...

    About those carb holes that can be drilled to 1mm, you mean these?
    IMG_1224.JPG

  3. #13
    Frequent Poster Miguelxj's Avatar
    Join Date
    Jul 2014
    Location
    Portugal
    Age
    36
    Posts
    160

    Re: Keihin CDK 2 - Reverse Jetting?

    Quote Originally Posted by wmazz View Post
    This is somewhat of a duplication of the above post. But the post I am quoting from
    demonstrates that a problem of some kind must exist. The dual carbs should have been
    a simple installation.



    There is no published Kawasaki pop-off recommendations that I am aware of. Only Polaris
    and the blue 42mm carb (SUDCO). I am certain the pop-off that works with the stock jetting
    is at least 26 to 30psi.

    If the engine was running lean with the stock pop-off and jetting, the real question is
    why? was the engine running lean.


    Bill M.

    A vacuum leak on the reed gaskets is a common cause for a problem
    that exists after an intake manifold switch. BM

    On the dozens of searches I did online, I found this info:

    http://www.carbparts.com/keihin/need...g_your_cdk.htm


    Although it doenst state any info on dual 38mm, it looks like their "brothers" 42 can be set / run on very low pop-off??


    I thought the main reason for running lean was related to the lower ability of the engine to create negative pressure (very very low restrictive FAs... they are just a mesh of stainless steel) thus not sucking fuel with the same strenght. Note that on higher RPMs it pulls strong and ripped me out of the handle bars once... So I was holding to that basic principle and believed that if you are running dual carbs, it is logical to have a lower pop-off than when you run a single carb, as you have one cylinder pulling (creating negative pressure) from each carb instead of 2 cylinders pulling from a single carb.

    Makes sense?? It kinda did to me...

  4. #14
    PWCToday.com Is My Home Away From Home wmazz's Avatar
    Join Date
    Jul 2013
    Location
    Riverside, CA
    Age
    57
    Posts
    2,339
    Blog Entries
    6

    Re: Keihin CDK 2 - Reverse Jetting?

    Do the low speed (pilot) screws have their o-rings installed?? There should be an
    o-ring followed by a short plastic tube, and then the spring?

    Current LS has 2 turns out and HS 2,5 turns out. It seems a bit too much so I tried some bigger jetting and no luck.
    I had to turn them out basically the same amount of turns.
    I got it running good with the following specs:

    140 main, 80 low and 55 mid-range, and 12 psi pop-off
    That jetting is rich. Either you have a large vacuum leak on both cylinders or you
    are trying to jet your carbs with an impeller that is too large.


    Currently with stock X2 nozzle and 15/18 skat-trak. Tried it first with a 15.5" solas. The 15/18 doesnt seem like its strugling as the
    RPMs get to aprox. 6.5K, just as the 15.5" was reaching...?
    Both impellers seem large to me, especially the 15/18. It should have more of a load, and
    produce at least 400 to 500 rpm less than a 15.5.

    Large impellers can feel strong pulling out of the hole, and flatten off on the top
    end. It may sound the same as an under-pitched impeller (U-PI), but an U-PI will
    pop out of the water really fast. The over-pitched impeller (O-PI), will feel like it
    has a lot of torque. The U-PI will rev out and will be down on top speed. The O-PI
    will flatten out and slowly accelerate. Often it is more difficult to recognize an over
    pitched impeller, and easy to notice a under-pitched impeller.


    On the dozens of searches I did online, I found this info:

    http://www.carbparts.com/keihin/need...g_your_cdk.htm
    That is the chart that I am referring to as Polaris and the Blue Sudco 42mm carbs.

    Although it doesn't state any info on dual 38mm, it looks like their "brothers" 42 can be set / run on very low pop-off??
    Any carb can be run at a low pop-off, so long as you follow a few basic rules.

    (1) The pop-off should never be less than the max fuel pump pressure of 7.5psi
    (2) The lowest pop-off that I recommend is 12psi.
    (3) The pop-off, low jet, low speed (or pilot) screw are all related, and the proper
    main jet is dependent on the size of the low speed jet.

    If you lower the pop-off, you should change the low jet by reducing the jet size. Then
    readjust the low speed (or pilot) screw, and increase the main jet size. Use the sum of
    the jet sizes to calculate the main jet. For example: the stock jetting is 70 low and 140
    hi (70 + 140 = 210). If you reduce the pop-off pressure, use the idle drop test to determine
    the low speed jet.

    Lets say the idle drop test produced a 65 low jet. Then subtract the new low jet size from
    the sum of the two jets; 210 - 65 = 145 main jet. If you follow this example, you will have
    expected results, and not a wild guess.

    I thought the main reason for running lean was related to the lower ability of the engine to create negative pressure (very very low restrictive FAs...
    hey are just a mesh of stainless steel) thus not sucking fuel with the same strength.
    Obviously, if you are running lean, there is a different cause.

    The quote is referencing the Mikuni manual, and for most watercraft it is no longer
    applicable!

    The Mikuni Manual author is referencing something that he experienced, and most likely
    prior to 1992. For example, up to 1991, Kawasaki was still producing flame arrestors that
    looked like some sort of Pumice. After 1991, the steel mesh flame arrestors that Kawasaki,
    Yamaha, and Sea Doo produced were not restrictive within the normal rpm range of 0 to
    7000rpm.

    Replacing these F/A with aftermarket F/A produced little or no gains. There may have been
    performance increases on the 97 1/2' Sea Doo 951. There was certainly gains in reliability.

    Note that on higher RPMs it pulls strong and ripped me out of the handle bars once... So I was holding to that basic principle and believed that if you are
    running dual carbs, it is logical to have a lower pop-off than when you run a single carb, as you have one cylinder pulling (creating negative pressure)
    from each carb instead of 2 cylinders pulling from a single carb.
    Yes, that idea is basically true, but it doesn't apply to your small diameter carbs. There is
    almost no reason to lower the pop-off on a set of carbs that were OEM dual carbs, and that
    were designed (jetted) for a 750 engine.

    OEM (original equipment manufacture) carbs for many engines are 34mm to 40mm. On many
    of these carbs, reverse jetting is possible, and pop-off's on single and dual carbs will run in
    the 65psi to 75psi range with 1.2 or 1.5mm seats. Despite the high pop-off on single and
    dual carbs, the engine will have significant gains in power.

    The larger carbs like 44, 46, 48, 50mm carbs when used as duals and triples, are when you
    can run into problems using a 115gr spring. A 95gr spring, and 1.5 seat will create the highest
    possible pop-off for most applications. The 48, and 50mm may require a larger needle and seat.

    Unmodified 44 and 46 on stock ported engines may be an exception, but as exhaust porting, and
    BDT increase, and loose piston to cylinder clearance, carbs can become more sensitive to pop-off
    (spring rate).

    Comparing jet specs for carbs with their low speed bypass holes modified (like Novi) will have
    different jetting than an unmodified 44 or 46mm, and the Novi's should not be used as general
    jet specs.

    I Recommend:

    ** Important ** Do not change the jetting, if you do not take my advice on the impeller
    size and vacuum leak tests.

    (1) Check the low speed screws for their o-rings, intake manifold, reeds, and reed gaskets.
    (2) Flat sand the carbs. Look at one of my posts on rebuilding Keihin carbs. Make certain the
    lever is 1 mm below the gasket surface.
    (3) Modify the carbs as I noted. Reinstall the stock jetting, and pop-off. The screws should
    start at 1 1/4 each.
    (4) Good places to begin when trying to jet the carbs richer is a 75 on the low, and a 45, 48
    on the mid. Use metric drills to modify jets if larger jets are difficult to find. Readjust the low
    (pilot) screw using the idle drop test.
    (5) On new set-ups I always recommend to begin with a smaller impeller. In your case a 9/17
    Skat Trak should be a good start. If you can not find one, have at least 3 degrees removed
    from your 15.5 leading edge.
    (6) If possible, purchase a tachometer. Your goal should be 6700 to 6900 rpm.
    (7) Purchase Polaris carburetor base gaskets.

    Good Luck!

    Bill M.
    Attached Images Attached Images
    Last edited by wmazz; 08-21-2016 at 10:06 PM.
    Horsepower == Speed, RPM != Speed



  5. #15
    PWCToday.com Is My Home Away From Home wmazz's Avatar
    Join Date
    Jul 2013
    Location
    Riverside, CA
    Age
    57
    Posts
    2,339
    Blog Entries
    6
    Last edited by wmazz; 08-21-2016 at 10:27 PM.
    Horsepower == Speed, RPM != Speed



  6. #16
    Frequent Poster Miguelxj's Avatar
    Join Date
    Jul 2014
    Location
    Portugal
    Age
    36
    Posts
    160

    Re: Keihin CDK 2 - Reverse Jetting?

    Hi Bill

    First of all, thank you so much for taking the time with this precious and valuable information!

    Im not confortable on repitching my 15,5 prop but it seems like it should be better to run this instead of the 15/18. I remember reading that its a common procedure to bore out the exit nozzle... do you recommend that also, since I'll have the pump apart?

    I have the stock XI tach that plugs directly on the wiring I'm using now, I know a digital one would be better but I guess this could sufice?

    2016-06-04 16.38.17.jpg


    Are these the Polaris gaskets? I found them with different ID sizes:

    http://www.ebay.co.uk/itm/Polaris-Ca...kAAOSwxYxUv2s4


    Will proceed as sugested and check all the points you mentioned. Im starting to bet my money on warped carbs. Manifold looks like new, reeds were OK and gaskets were all new...

    wait a minute........ I'm forgetting something....... I'm using 2 plastic caps on both the manifold oil nipples... they are secured with zipties and were ment to be connected to the primer (waiting on a T fitting to finish this). Need to check that too.........

    IMG_1780.JPG

  7. #17
    Frequent Poster Miguelxj's Avatar
    Join Date
    Jul 2014
    Location
    Portugal
    Age
    36
    Posts
    160

    Re: Keihin CDK 2 - Reverse Jetting?

    I Recommend:

    ** Important ** Do not change the jetting, if you do not take my advice on the impeller
    size and vacuum leak tests.

    (1) Check the low speed screws for their o-rings, intake manifold, reeds, and reed gaskets.
    (2) Flat sand the carbs. Look at one of my posts on rebuilding Keihin carbs. Make certain the
    lever is 1 mm below the gasket surface.
    (3) Modify the carbs as I noted. Reinstall the stock jetting, and pop-off. The screws should
    start at 1 1/4 each.
    (4) Good places to begin when trying to jet the carbs richer is a 75 on the low, and a 45, 48
    on the mid. Use metric drills to modify jets if larger jets are difficult to find. Readjust the low
    (pilot) screw using the idle drop test.

    (5) On new set-ups I always recommend to begin with a smaller impeller. In your case a 9/17
    Skat Trak should be a good start. If you can not find one, have at least 3 degrees removed
    from your 15.5 leading edge.
    (6) If possible, purchase a tachometer. Your goal should be 6700 to 6900 rpm.
    (7) Purchase Polaris carburetor base gaskets.

    Good Luck!

    Bill M.
    Also, what would be a good number to start on the pop-off pressure? I have a couple of different springs I could try before ordering new ones but have no idea on stockish setting.

    The carbs have standard 1.6 NS.

    The lower I could go right now (without ordering and waiting for them) on jetting is:

    Main 140
    Pilot 80
    Mid 45
    Last edited by Miguelxj; 08-22-2016 at 07:55 AM.

  8. #18
    PWCToday.com Is My Home Away From Home wmazz's Avatar
    Join Date
    Jul 2013
    Location
    Riverside, CA
    Age
    57
    Posts
    2,339
    Blog Entries
    6

    Re: Keihin CDK 2 - Reverse Jetting?

    You have a small pin Xi cylinder? Right?

    Which pump nozzle are you using? The 650 X2 nozzle, or the 750 nozzle?

    I am going to assume you have the 650 x2 nozzle with the 15.5 impeller.
    If you can bore 2.5mm's from the nozzle, that would help.

    Gaskets: http://www.ebay.co.uk/itm/Kawasaki-K...MAAOSweW5U9ozI

    POP-OFF: As high as you can. Preferably 26psi or greater. You will need to
    lean out the low (pilot) screw to 1/2 to 1/4 turns out.

    Since the low speed jet is 2 to 4 sizes too large, the hi-speed screw will
    most likely need to be leaned out also. Be cautious, but start the Hi-speed
    screw at 1 turn out; instead of 1 1/4. I believe it will need to be turned in
    (because of the low jet) to 3/4, and maybe 1/2 turn out.

    Testing: Where do you ride or test at? does it have a no wake zone or speed
    limit out to the buoys. In the U.S., we have 5 mph or no wake zones at public
    lakes and reservoirs.

    The best place to test is at a location where there are no speed limits near
    the shoreline. Take off from shore and go out 50 meters. Then turn around
    and go back to shore. Within that 100 meters, you should have a good idea
    of what changes need to be done.

    If the ski isn't running well on top end; keep in mind that you can only make
    changes with the low speed (pilot) screw, and the hi-speed screw (Reducing
    pop-off will only make it worse).

    If you run into problems with the top end, and you can not adjust it out within
    my guidelines, go home and fix it! Please do not fall into the trap many riders
    have! If you tell yourself that if you just take it easy, you can ride all day.
    Sounds silly, but it happens a lot!

    Pre-Mix Oil: Do you have a high quality MX oil?? If so, 20:1 may help lean out
    your jetting temporarily.

    You have a small pin Xi cylinder? Right? ~186 deg exhaust ports.

    Which pump nozzle are you using? The 650 X2 nozzle, or the 750 nozzle?

    The 80 low jet and a low pop-off psi will reduce your peak rpm. But if you use
    my guidelines of 26 psi pop-off or greater, low screw 1/2 to 1/4, hi speed 1
    to 1/2, 20:1 oil mixture, 15.5 and the pump sealed to the hull with the stock
    x2 nozzle. That is a decent starting point, and after trying it, you may need
    to wait for a stock low jet and spring. Maybe the nozzle bored.

    Follow my instructions for flat sanding the carbs (with the rack removed). If you
    do not have a flat sanding surface, I can teach you how to make a cheap one.


    Bill M.
    Last edited by wmazz; 08-22-2016 at 09:54 PM.
    Horsepower == Speed, RPM != Speed



  9. #19
    Frequent Poster Miguelxj's Avatar
    Join Date
    Jul 2014
    Location
    Portugal
    Age
    36
    Posts
    160

    Re: Keihin CDK 2 - Reverse Jetting?

    Hi Bill,

    Couple of news:

    I am currently waiting for a 9/15 solas prop, gonna swap it for this 15/18.

    I got the carbs out yesterday after work and just as you said: wet gaskets:




    The bottom of the carbs look decent. Could this be caused by a misalignment on the straight bar thar holds both carbs??




    Sent using Tapatalk

  10. #20
    Frequent Poster Miguelxj's Avatar
    Join Date
    Jul 2014
    Location
    Portugal
    Age
    36
    Posts
    160

    Re: Keihin CDK 2 - Reverse Jetting?

    Quote Originally Posted by wmazz View Post
    You have a small pin Xi cylinder? Right?

    Which pump nozzle are you using? The 650 X2 nozzle, or the 750 nozzle?

    I am going to assume you have the 650 x2 nozzle with the 15.5 impeller.
    If you can bore 2.5mm's from the nozzle, that would help.

    Gaskets: http://www.ebay.co.uk/itm/Kawasaki-K...MAAOSweW5U9ozI

    POP-OFF: As high as you can. Preferably 26psi or greater. You will need to
    lean out the low (pilot) screw to 1/2 to 1/4 turns out.

    Since the low speed jet is 2 to 4 sizes too large, the hi-speed screw will
    most likely need to be leaned out also. Be cautious, but start the Hi-speed
    screw at 1 turn out; instead of 1 1/4. I believe it will need to be turned in
    (because of the low jet) to 3/4, and maybe 1/2 turn out.

    Testing: Where do you ride or test at? does it have a no wake zone or speed
    limit out to the buoys. In the U.S., we have 5 mph or no wake zones at public
    lakes and reservoirs.

    The best place to test is at a location where there are no speed limits near
    the shoreline. Take off from shore and go out 50 meters. Then turn around
    and go back to shore. Within that 100 meters, you should have a good idea
    of what changes need to be done.

    If the ski isn't running well on top end; keep in mind that you can only make
    changes with the low speed (pilot) screw, and the hi-speed screw (Reducing
    pop-off will only make it worse).

    If you run into problems with the top end, and you can not adjust it out within
    my guidelines, go home and fix it! Please do not fall into the trap many riders
    have! If you tell yourself that if you just take it easy, you can ride all day.
    Sounds silly, but it happens a lot!

    Pre-Mix Oil: Do you have a high quality MX oil?? If so, 20:1 may help lean out
    your jetting temporarily.

    You have a small pin Xi cylinder? Right? ~186 deg exhaust ports.

    Which pump nozzle are you using? The 650 X2 nozzle, or the 750 nozzle?

    The 80 low jet and a low pop-off psi will reduce your peak rpm. But if you use
    my guidelines of 26 psi pop-off or greater, low screw 1/2 to 1/4, hi speed 1
    to 1/2, 20:1 oil mixture, 15.5 and the pump sealed to the hull with the stock
    x2 nozzle. That is a decent starting point, and after trying it, you may need
    to wait for a stock low jet and spring. Maybe the nozzle bored.

    Follow my instructions for flat sanding the carbs (with the rack removed). If you
    do not have a flat sanding surface, I can teach you how to make a cheap one.


    Bill M.
    Yeah, stock Xi 1994 750 sp!

    Running stock X2 pump and nozzles. As I had to remove the 15/18 yesterday, I brought the exit nozzle with me and gonna bore this out in a lathe. 2,5mm should be enough! currently 15,5 SOLAS prop installed.

    Testing: We do have rules about being very cautious while accessing or leaving shore, specially when there is a public beach. As I usally test the ski in the middle of the week, this should be no problem.

    Pre-mix: running PENZOIL fully synth biodegradable (yellow bottle). These (about 5 or 6 bottles) came with the race ski I bought last year. Mixing gas & oil at a 40:1 ratio. You're sugestting I run 20:1?? That results in a 5% mix ratio, isnt it a bit too much?
    I also have access to a very good MX racing 2T oil, but I am not using it because I thought it wouldn protect the engine as good as a TCW3 oil...?

    Gonna flat sand everything this weekend, gotta completly disassemble the carbs as they need to be cleaned up good afterwards. Still wondering if the rack - wich I removed when I was rebuilding the carbs and bolted it back together with the carbs off the engine - could be playing a big role on not allowing the carbs to sit flat in the manifold......

    Thanks for all the input man.

Page 2 of 5 FirstFirst 1234 ... 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