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  1. #1
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    Helpful tips on the infamous CDKCV carbs. Ultra 150, Zxi, STX

    I've done a LOT of these over the years and thought I'd share some helpful tips for those who are trying to make a set of these CDKCV Keihin carbs work properly.
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    The first step would be to disassemble EVERYTHING for cleaning and inspection. There are rebuild kits available that come with the basic parts. The vacuum slide parts are not available any more. If you need anything related to those parts you will need to source another set of parts carbs.

    Many times the needle seats get really stuck in the carb body. You NEED to get those out to clean the passages and the micro screen filters located under them. Spray a bit of penetrating lube and find a wood screw just the right size. You want it to screw into the seat but without requiring much force. I think it's a #8 shank screw. Just screw it in a little bit and pry the seat out with needle nose pliers.
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  3. #3
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    These carbs have a pilot screw adjuster but they are hidden behind plugs. Use a 1/8" drill bit to carefully drill through the plug. Then screw that #8 wood screw in a little and pull the plug out to reveal the adjuster. Spray a bit of lube down in there and lightly seat the screw while counting the number of turns. I've found most to be from 3/4 to 1.25 turns out. THEN...you can remove them to clean out those idle circuit passages.
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  4. #4
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    The problems I usually find with these carbs are usually in the vacuum slide portion. Clean the tiny metal orifice in the outer edge of the diaphragm. Be careful blowing carb cleaner or air through it. Too much pressure will blow it right out of the diaphragm and the tiny bit will never be found again!! Also make sure to clean the passage leading to this orifice.
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  5. #5
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    The vacuum slides can wear, and so can the piece they slide IN. If they look like these.......they are worn out and likely sticking as they try to move up and down. This will cause bogging, hesitation, and overall just poor running. The slide 'guide' also has an o'ring seal behind it. If this seal is dried up and cracked it will cause running issues too.
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  6. #6
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    Another fairly common issue I find on these is worn out needles on the slide. This needle controls the fuel flow out of the main jet from just off idle all the way to WOT. Vibration through the years seems to wear the needle away at the top hidden from view! There is a 10mm plastic nut down in the slide. They are just snug, DON'T use a ratchet or drill on these! Just unscrew the nut and tip the slide over. The needle will fall right out. These were on the set I just did. The center one is normal. The other two are worn slap out. One of them is almost worn to the point that the needle can actually fall out INTO the carb throat while at WOT.....I've seen this before! That top washer or shoulder area being worn like this also causes uneven fuel flow from off idle up to about 1/4 throttle because the needles are NOT all lifting up evenly. Don't lose the small springs INSIDE the plastic nut. And when you screw the plastic nut back into the slide just snug it by hand....NOT very tight....the plastic nut will snap off at the threads.
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  7. #7
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    Very nice write-up!

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  9. #8
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    And finally on to the fuel pump. Check or replace the diaphragm, clean everything, and replace this o'ring.

    If anybody else has anything to add please feel free to do so.
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  10. #9
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    Quote Originally Posted by steve45 View Post
    Very nice write-up!
    Thanks steve45.

    ALSO....use a shop vac on the engine side of the carbs to test vacuum slide operation. Just stick it on the carb and open the throttle. You will see the slide rise open. Depending upon how stout the vacuum is the slide may open all the way or maybe only 1/2 way. Just make sure they all slide smoothly with variable throttle opening and all 3 slide the same. DO THIS BEFORE you bolt them back on.

  11. #10
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    don't fall victim to the mod demon on the carbs either...Don't change the air intake system, and for pete's sake NEVER remove the choke plates on these to install primers if your ski happens to be a bit hard to start
    Drill a small hole centered over the center carb throat in the flame arrestor and use that to allow a squirt can to spary some premix down in there. you only need one cylinder.

    When I lived back east when dinos roamed the earth, the AAA wrecker I drove had a hose terminating at the grill to spray ether into when it got so cold they would start, but really wack the battery when doing so. I'm talking below 20 weather for a month straight

    once run and hot, they would be good until it sat outside for 12+ hours

    treat your cv carbed kaw the same way..you can use the squirt can to prime it up if need be, but it will likely be good the rest of the day

    great write up, especially using the sheetrock screw to help get the seat out

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