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  1. #1

    '96 900 ZXI - no power and low top rpm

    Hey guys, this season I picked up a '95 seadoo hx that the seadoo forum on this site has been helping me out with. At the same time I picked up a '96 900 ZXI. The seadoo is finally running engine wise, so its time to turn to the ZXI.

    Starting cold isn't too much of a problem. It needs the choke but it usually starts with choke and a little gas. Once in the water it needs to be choked to 'warm up' or else you can pull the throttle all the way and it barely moves. Once its warmed up it is a complete slug coming out of the water and only ever hits a grand top RPM of 5500 on smooth water.

    The trim doesn't work, and is pitched nearly all the way down. I want to get the engine running better before I work on this.

    You can yank the throttle all day long and it just takes forever to get there. However, it doesn't like it if you slow down too quickly. Coming from full throttle and letting the throttle snap out on the spring is about the quickest way to kill the engine. After it dies from that, if is incredibly finicky about restarting. Hit the starter and it may start right back up, but the instant you give it gas it will die again. Other times it doesn't want to start back up and even goes so far sometimes as to require a bit of choke. Not all the way, but maybe 1/4 choke.

    idle speed seems to be way low. tach seems to read as low as <500 rpm at idle. If it idles, anyway, which it doesn't always want to do.

    Where would you fine folks suggest I start?

  2. #2
    steve45's Avatar
    Join Date
    Feb 2008
    Replace the fuel filter(s) (there's an inline one and two in the tank). You might try running on Reserve first and see if it helps. After that, time to overhaul the carbs.

  3. #3
    Changing to reserve doesn't make any difference. I'll change filters first. Do you think I'll get away with pulling the carbs and just running copious amounts of carb cleaner through them or do I need to spend the ~$150 for rebuild kits?

    I forgot to mention that I have had it backfire once or twice after it died on me. Its not consistent or common, but I have had it happen. Does that change your suggestion any?

  4. #4
    TexasZ's Avatar
    Join Date
    May 2012
    Near San Antonio, Texas
    Quote Originally Posted by JheregJAB View Post
    Changing to reserve doesn't make any difference. I'll change filters first. Do you think I'll get away with pulling the carbs and just running copious amounts of carb cleaner through them or do I need to spend the ~$150 for rebuild kits?
    It's possible for you to get by with just cleaning the carbs...there is a screen filter in them below the needle and seat that gets gunked up. Part # 49019 on this diagram...
    It's also extremely important that the arm over the needle and seat is set right. That's 16055 on that diagram. Use the search here for detailed instructions for setting that on CDK II carbs. Take a real close look at all the carb parts, especially the replaceable ones. Sometimes you just need to replace a few specific parts and not have to buy the whole kit.

    The older type fuel lines are usually replaced as the ethanol mix in gas eats them up on the inside and also allows a slime to grow in there. Check them out closely.

    I'm assuming that you drained the old gas out and replaced with fresh gas. Also while you are cleaning the filters on the pickup tubes inside the tank, check to make sure it doesn't have the usual layer of old gas 'syrup' on the bottom of the tank that needs to be cleaned out.

    I forgot to mention that I have had it backfire once or twice after it died on me. Its not consistent or common, but I have had it happen. Does that change your suggestion any?
    Backfiring could be caused by cracked or chipped reed valve pedals.

  5. #5
    This is how I run a jetski shop in the desert nmpeter's Avatar
    Join Date
    May 2008
    Elephant Butte New Mexico
    rebuild the carbs..that ski is how many years old?

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  7. #6
    Thanks so much for the help guys! Were the old fuel lines on kawasaki ski's the same grey tempo ones that were used on seadoos? I just did the fuel lines and carbs on the hx I mentioned. If the old lines were not grey then I might replace the ones that are on this ski - is there anywhere I can look for sizes/lengths? It was very helpful for my hx that I knew exactly what to get before driving to the ski. Its located about a 30-40 minute drive from where I live, and its in a little town with no shop. I therefore try to plan out repairs and bring everything I need with me, if I forget something it can sometimes be 2-3 days before I make it back out that way.

    Would you be so kind as to point out the reed valves in a diagram? If I'm going to have the ski pulled apart I figure I might as well check them if I can. I took the ski out a little bit this weekend to see if I could do some more diagnostics and the backfiring was worse than before. It only backfires when trying to start though, not when running.

    I was able to determine from the plugs that the ski is running very heavily on the front cylinder and not very much at all on the rear two, in case you're curious. I disconnected the plug wires one at a time and tried to ride the ski without them. rear-most cylinder disconnected I got about 4200 rpm on the tach and couldn't get on plane. Middle cylinder disconnected and I hit about 5200 and was able to get on plane. Front cylinder disconnected and I could barely get away from the beach. Plug color confirmed that the rear two cylinders are not running correctly. Both rear plugs were wet when I pulled them out, but it looked more like wet with oil than with fuel. Almost like they aren't getting enough fuel to fire but the oil injectors are still working.

  8. #7
    So I pulled the carbs out. How in the world do I get to the screens in the parts diagram? Am I just being too gentle with these things?

    I pulled the screws out to get the cover off, and then the one screw in the middle. When I did that the section started to wiggle a little but didn't want to pull away. I then took the other screw off that lever and carefully removed the needle and spring as well. This did nothing for removing that section from the main carb body so I could access the screen, however. The parts diagram lists a low speed and a high speed jet (parts #92063/A/B and #1615. These carbs only seem to have one of those, though there is a space that looks like it might fit another. Its hard to tell from the parts diagram which one I think I have, but I think it would be the one labeled Main. Are these jets adjusted by turning them? If so my middle cylinder is set in a different place than #1 and #3.

    These carbs actually look to me to be in pretty darn good shape. I'm no expert (obviously) but they don't appear beat up. All the gaskets and seals seem to be in place, and they aren't particularly hard or anything. I also haven't noticed any gunk in them at all. I also noticed with my head in the ski that the fuel line "looked" rather new.

    The set up of these carbs is interesting - fuel pumps on 1 and 3 along with inlets, their return lines are hooked to #2, and #2's return line runs back to the gas tank. The security-style screws used in the pump sections are... annoying.

  9. #8
    Since the carbs seem to be in such good shape to my untrained eye, I started looking elsewhere for issues. (Though I still haven't managed to get to the screens. I'm too afraid to accidently change the settings on the carbs and end up causing more harm than good.) I ran into plenty of threads saying that bad reed valves will allow blowback, the primary symptom of which is the flame arrestor being coated in gas and oil. When I pulled the carbs, guess what? the flame arrestor was covered in gas and oil.

    So I started looking deeper, and I found a couple threads in various places claiming that bad reeds can cause low pressure on the pulse lines for the fuel pump, and therefore a lack of power and a low top speed.

    I have ordered new reeds and once they get here I'll go pull the old ones out and replace them. I'm hoping for the best.

    One question I do have though, is that I also find people claiming that bad reeds will not effect a compression test. Could someone explain how that works? I thought the whole point was the reeds sealed the chamber to prevent gas from escaping back into the carbs. If the reeds are cracked/chipped/broken then they wouldn't seal, and wouldn't that cause low compression readings due to the pressure escaping out the reeds?

  10. #9
    This is how I run a jetski shop in the desert nmpeter's Avatar
    Join Date
    May 2008
    Elephant Butte New Mexico
    yeah, you have to watch out for various experts who refute what common sense tells most folks.

    bad reeds can certainly impact a compression test. If half the charge slips back out, your compression numbers will be lower..but you already know the reeds are bad due to excessive blowback. Same way we can tell when a Seadoo rotary valve is screwed

    so far you're doing pretty well.

    Now as to gaining access to the fuel filter screen..the carbs are precision items so not a lot of slop to show you the way and to worry about breaking stuff is a good sign.

    Once that big center screw is out you should be able to separate the fuel chamber from the rest of the carb body. Might need some help with a couple of very light taps from a PLASTIC hammer. PLASTIC that there slick?

    Kawasaki did not use tempo fuel no need to go thru that.

    You should see a good amount of fuel coming thru the return line. You can splice in some clear braided hose to check flow if you want to see how much. I disconnect the return line and run a hose into a container and run the engine. Standard safety practices should apply if you do it my way ( a big fat co2 bottle sitting next to you just in case)

    For the moment, with the overall condition of the carbs, I'd say replacing the reeds could put you back on the water, specially if when you remove them they are warped/cracked/missing. That often happens during a water ingestion incident.

  11. #10
    I got the old reeds out yesterday evening. I've got the new ones in the cages and I'm hoping to put them on the ski and test later this week. If I don't get to it this week then it'll be probably early next week.

    In the meantime, enjoy the pictures. The reeds are setup in the pictures according to the cylinder they were pulled out of with the left-most being #1 cylinder toward the front of the ski. By the way, these reeds are completely different than the ones I ordered. Are the reeds I took off aftermarket or has the design just changed? I ordered part 12022 on this diagram:
    Click image for larger version. 

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