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  1. #1

    1999 Utra 150 low RPMs

    I am trying to locate the source of my Ultra 150's low rpms. I just finished a rebuild, and the ski runs great on the trailer. I went to the lake to start the break-in process, and found that the rpms will not climb above ~3,200.

    I have pictures of the plugs, which I assume will not indicate much since they have less than an hour on them. They are running on pre-mix as well as the oil from the pump. Plugs are from cylinder 1, 2, 3 from top to bottom.

    I also have a picture of the pump, which measures to be within spec. I cannot move the impeller forward or back (into or out of the housing) by hand. I am assuming that pump is OK, but i'm not sure if the wear marks on the housing are normal??

    I thought that it may be the water temperature sensor, but I bought one, and it seems to test out the same one as the original one. (I have not tried the ski with the new sensor yet)

    The carbs were bought "remanufactured", so at this point I am assuming that is not the issue, but I'm not sure how to test them.

    Any advice on what else to check?
    Does the pump look like it needs a rebuild?

    Any advice is appreciated.
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  2. #2
    Those look like iridiam spark plugs, try the standard copper plug. Pump looks great, that is not going to cause your low rpms.

    Temp sensor will put in limp mode, but will rev much higher then 3k.

    Who remans carbs for these? I have yet to see any company due this.

    Does it run better with choke applied?

    Lets start with the basics, give it a compression test to see where the engines health stands (i you said it was just rebuilt, but lets just make sure). Btw who did the rebuild and what parts used?

  3. #3
    The plugs are NGK R6918C-9. Being a 1999 I knew that there were two possible plugs, one for an older hull #, and one for a newer Hull #. I couldn't remember what the HIN cutoff was, so I erred on the side of caution, and bought the plug for the older HIN. For reference, my HIN is 42756, so I suppose the other plugs would have been fine.

    I actually did the rebuild myself, and used WSM parts. I know, should have used Kawasaki....
    I checked the compression after the rebuild, and before any startup. The readings were 110 across all three cylinders on my gauge. I figure that wasn't bad for the rings not being seated yet.

    Yeah, actually I used the wrong term, the carbs were rebuilt, not remanufactured. When I bought the carbs (the old ones were trashed from sitting outside for several years, uncovered) the man I bought them from said he had taken them apart, cleaned them, new diaphrams, etc. He rebuilds his own, and also rebuilds them to re-sell. They were clean, and appeared to be in perfect condition. I did not take them apart though.

    I didn't try running it with any choke once it started.

  4. #4
    A follow-up: I went out and started the ski again this evening on the trailer. I removed the FA, and used a mirror to look down into the carbs while it was running. I gave it some throttle. Quite a bit actually, and I did not see any of the black slides move. When I shut the ski down, I moved the slides by hand, and they moved easily. So I have a question. I am assuming that the slides should move when the engine is throttled up (even on the trailer). So what would cause these not to move? I guess the actual question is - what should I do next?

  5. #5
    Pull carbs and inspect slides, they can be very tricky to seat correctly an majority of the time get kinked. I use alittle super glue to hold the diagrams inplace then put spring and cap on.

    They should move, if you see the port on the aluminum intake, blow with compressed air and the slide should move. If it does not the diaphragms are ripped or installed incorrectly.

  6. #6
    I'll pull them and check. Thanks!

  7. #7
    steve45's Avatar
    Join Date
    Feb 2008
    No problem with iridium plugs, they're less prone to fouling than massive electrode plugs.

    Check to see that the little metal orifice on the slide diaphragms is clear.

  8. #8
    I'll check the orifice(s) too. Thanks!!

  9. #9
    You can do the compressed air test with carbs still in ski.

  10. #10
    Well, that would certainly be preferable. Can you guide me through that? I'd rather not take them back out unless I have to.

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