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  1. #1

    Carb Diaphram Question

    My 900 zxi stopped getting fuel and i found both diaphrams on the fuel pumps were torn in the upper right hand corner. I know this is a problem and not my question.

    I was wondering if there is something that caused both to tear (i.e. riding it too hard, not letting it warm up enough before riding, a defective part, etc.) or is it just that one failed and then after a while the other failed and when the motor shut off I quickly became aware of the problem?

    I just bought the ski and have only had it out once so I do not know if there was any performance change when the first diaphram may have dropped out.


  2. #2
    steve45's Avatar
    Join Date
    Feb 2008
    Well, it's probably over a decade old. That usually means that the rubber parts go bad.

  3. #3
    I understand that the age is a likely cause. It just seemed odd that not just one was blown but both. Could be a coincidence, but I wanted to make sure it was just age/wear-and-tear and not something else that will cause the new ones to blow out right after puting them in.


  4. #4
    How long should it take to prime the fuel lines if they were dry. I pulled the line and put my finger over the end and I feel suction. I put the choke on and cranked it for five 10 second bursts and still nothing. I stopped to charge up the battery to keep it strong.

  5. #5
    steve45's Avatar
    Join Date
    Feb 2008
    Hard to tell, did you put the new diaphragms in? Of course, it may take longer the first time with completely dry carbs.

    Put in primers and you'll have instant starting.

  6. #6
    yes I put new diaphrams in. I have tried for a while now and recharged the batter a few times. It still does not seem to want to start. I am wondering if something else is wrong besides just the diaphrams. I siphoned fuel up through the line then attached it to the carb. It sputters then backfires and does not continue. I have plenty of compression and good spark in all the cylinders (I have checked and triple checked).

    Any suggestions?

    Also, will cranking the engine over a lot cause the oil injection to suck excess oil into the cylinder causing the gas to foul in the cylinder, exit into the exhaust pipe, and eventually backfire?

    I may consider a primer. Would you recommend one of those three carb specific pumps or just an inline bulb? Also, how do those three carb hook-ups work. Are you essentially removing the choke and replacing it with at pump?

    Thanks for the help!

  7. #7
    steve45's Avatar
    Join Date
    Feb 2008
    Is it backfiring out the exhaust, or the intake? I would think out the exhaust would not be likely because you'd foul the plugs and they wouldn't even fire. Out the intake could be bad reeds or flywheel shifted on the crank. Try pouring a teaspoon of gas down each carb throat.

    I don't know what year your 'Ski is, the later ones had CV carbs on which you really shouldn't remove the chokes. This was on the 1100s and 1200s, don't know about the 900s.

    I like to install the primers directly into the intake manifold. That works well with the CV carbs and you can remove the carbs without messing with the primer hoses.

  8. #8
    I already poured about a teaspoon down each of the carbs and I believe it may have been after that it back fired. I am pretty sure it was out of the exhaust. It blew some moisture out that was left in the muffler, since I was unable to flush it, being that the motor was not running when I got it home.

    When I put the teaspoon in the carb it only sputtered mostly and sounded like it wanted to start but was only firing while the starter was turning the motor. It started up once and I shut it off after about 5 seconds of running because I wasn't quite ready with the hose. I then killed ignition, then it only sputtered when i tried again, and now does nothing again. I think it was just working off the fuel i put in the carbs and is still not pulling gas from the tank for whatever reason.

    I have heard of people puting their hand or a plastic bag over the air intake to prime their ski. Is that a good idea?

    my ski is a '96. It has a Keihin CDK II triple carb with two fuel pumps (one on each carb on the ends with pulse lines to the middle carb). How much pressure should the fuel pumps be pulling? Should they easily suck fuel out of a bottle of gasoline if you set it next to the ski?

    Installing the primers seems like a good idea but I would still like to determine why it is not working without them, because before the diaphrams blew, it would start after 2 or 3 seconds on the starter every time and maybe 5 seconds on the first start after it had been sitting for a few days. Just seems like there is a bigger problem if it is functioning differntly now.

  9. #9

    I got it running. I kept adding fuel in the carb till i got it running enough to give the throttle a little pull and i guess it was enough to get the system primed, b/c now it runs great and starts right up. One turn of the starter and it idles smoothly. I guess it just needed a good prime. I'm gonna take it out on the water for a test run. Ive got a friend going with me so he can tow me back if I have issues.

    I think i will look into installing a primer kit because the choke was obviously not enough by itself for starting it dry.

    Thanks for all the help and advice from your experience. I appreciate it.

  10. #10
    Just wanted to follow up with this.

    I took the ski out and it was running fine then it turned off on me while I was out on the water. It eventually started and ran fine for a while again. I then shut it off and took a mid day break. When I went to start it again, it would not fire up. I took off the spark arrestor and poured fuel into each cylinder and got her fired up again.

    I then tried running around again. It ran great again and after a while suddenly majorly lost power. I would not get up on plane. I thought I may have picked up sea weed that was bogging it down, so I pulled it out of the water on the trailer. I found a little sea weed but not enough to keep me from getting on plane.

    I decided it was time to clean the whole carb and disassemble everything for inspection. The last owner probably did not run the fuel out of the carb when he last winterized it. There was a decent amount of varnish but not enough to damage the metal, but could have been enough to clog a jet or something.

    I cleaned everything and as I was putting one of the fuel pumps back together I noticed on of the check valves was not closed. I flexed the metal a little to give it a good seal again and put everything back together.

    I made sure all the fuel was drained from the entire line, including fuel filter bowl before checking it. I then put the choke on and watched as the machine quickly sucked fuel through the system and started right up!

    It is running much smoother now and the throttle is much more responsive! I cannot wait to take this thing out on the water. I am hoping this means it will be pumping out more power!

    Again, thanks for all the help. Just wanted to let you know what I found to be the issue.

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