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  1. #1

    Low speed wot studder

    Hi all.

    Got an ultra 310 with 20 hrs on it, 8 of them with me on it.

    Today, after a 45 min run, I suddenly started having some funny throttle response when sitting idle then giving wot. It shudders a bit and sprints to 20 kmh, then shudder some more, if I by that time let go of the throttle and immediately after give it wot again, then it flies like normal.

    I went in for a break for 10 min or so, then out again. When I started it, in ran idle rough and shuddering for the first 5 seconds or so, then fine. Did a bit of a run around, and noticed the weird shudder after idle again a few times. Decided to take it out of the water to check it out.nothing to see anywhere inside. Hull bone dry inside too.

    Drove home, 1 hour drive, gave it an external wash, then started it to flush it and got same shudder and rough idle for 5 sec or so. Rev it a little and it goes smooth like always.

    Any ideas? I'm guessing that it could be a leaking injector, how could I check it?

    Should I not bother and just drop it in for warranty repair?


  2. #2

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    exhaust filter?

  3. #3
    Quote Originally Posted by shore View Post
    exhaust filter?
    Feel free to explain a bit more?

    Do you think it might have blocked or something?

    How can anything with the exhaust filter result in low rpm rough idle sorta thing but not influence engine output at speed? Ski still seem to do top speed like beforehand

  4. #4
    "just sayin".. jetdave56's Avatar
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    Start with the simple checks before you start taking the whole thing apart...

    1)Are all 4 wire leads plugged in snug in their respective coils,same with spark plug boot on their plugs?

    2) Put in fresh full tank of 93 octane

    3) was anything done or taking apart since you owned it?

    If nothing changes then might have to examine the exhaust filter as mentioned though 20 hrs sounds little low to have these issues..

  5. #5

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    Quote Originally Posted by DKGuffe View Post
    Quote Originally Posted by shore View Post
    exhaust filter?
    Feel free to explain a bit more?

    Do you think it might have blocked or something?

    How can anything with the exhaust filter result in low rpm rough idle sorta thing but not influence engine output at speed? Ski still seem to do top speed like beforehand
    hard to say but anytime there is a starting issue, look at that filter.

  6. #6
    Quote Originally Posted by jetdave56 View Post
    Start with the simple checks before you start taking the whole thing apart...

    1)Are all 4 wire leads plugged in snug in their respective coils,same with spark plug boot on their plugs?

    2) Put in fresh full tank of 93 octane

    3) was anything done or taking apart since you owned it?

    If nothing changes then might have to examine the exhaust filter as mentioned though 20 hrs sounds little low to have these issues..
    Checked all of above, fuel same as last run with no problems over 23km distance, 40 min run. Fuel 6 days old shell 98 octane.

    No mods to ski, and ski only used for kawasaki Australia promo shots before I got it.

    As far as I know, the ski has never been taken apart.

    I got 2 years 8 months warranty left...

    Filter, warranty?

  7. #7
    benjahw benjahw's Avatar
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    New plugs possibly

  8. #8
    So, when I get home tonight after work, I'm gonna try start it again. If it still sputters when I start it up, then I will immediately shut it down and check spark plugs for wetness (might be able to tell me if one plug doesn't ignite or if one injector is leaking.

    If I get nothing out of the above, then I will check the exhaust filter.

    I'll report back my findings. Thanks a lot so far.

  9. #9
    Quote Originally Posted by DKGuffe View Post
    Quote Originally Posted by jetdave56 View Post
    Start with the simple checks before you start taking the whole thing apart...

    1)Are all 4 wire leads plugged in snug in their respective coils,same with spark plug boot on their plugs?

    2) Put in fresh full tank of 93 octane

    3) was anything done or taking apart since you owned it?

    If nothing changes then might have to examine the exhaust filter as mentioned though 20 hrs sounds little low to have these issues..
    Checked all of above, fuel same as last run with no problems over 23km distance, 40 min run. Fuel 6 days old shell 98 octane.

    No mods to ski, and ski only used for kawasaki Australia promo shots before I got it.

    As far as I know, the ski has never been taken apart.

    I got 2 years 8 months warranty left...

    Filter, warranty?
    Hi again.

    So since I first posted this thread, I found that the rear of the impeller had a minor little bend to it, and some leading edge scratches. I pulled the pump out and had the impeller fixed, repitched and balanced.

    Took her out for a spin yesterday in the cold, but, behold still got the same weird stutter going. If anything it might seem slightly worse, or maybe it's just me getting more aware of it. It does it 100℅ of the time if I sit idle, then give it full throttle. Ski jumps out of the water as usual, then suddenly loose all power in a couple of jerks, then half a second later returns to full power and nearly rips my arms off..

    I noticed that the shudder happen around 4000rpm, reaching around 20-50 kmh.

    I put a speed delimiter on yesterday too, top speed is 113kmh in fresh water.

    I have yet to check plugs and exhaust filter. Fuel was replaced before testing yesterday. First runs were with shell 98, yesterday's run was BP 98.

    Ski has 22hrs on it now.

    I'm gonna pull it apart tonight and check the filter. Any other suggestions are welcomed.

  10. #10
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    My advice is to quit riding it till you find out what the problem is....

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