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  1. #1
    Gus13letter's Avatar
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    HELP!! - Ski shudders after IC, SC, and waterbox mod.

    *** Update 6/22/08: ***
    Took it out today and I need some help please.
    With both seats on if the ski is given gas sudenly or off power sudenly the whole ski shudders really bad.
    With the rear seat off it is noticable, but not so bad. I checked everything even cut the intercooler pipes to be more in line to have a more free flow but same problem. Ski performs great other than the off throttle shudder. I know I need a new prop, 8200 RPMs (on the rev limiter) and 71.5 on the GPS.

    I must say I first noticed this when I flushed the ski for the first time after the mods.
    Could it be the way my waterbox is cut? When I removed it today to make room for the GH Shorty on the way I noticed the waterbox was completely full of water even after reving it up.


    ** ORIGINAL POST **
    I just installed an XS intercooler, Riva Stage III supercharger, 42Lb injectors, Riva catch can, and gutted my waterbox. I fired it up without the seats to make sure everything was ok. All looked ok. When I put both seats on and I reved it up, the ski seamed to shudder like something was out of balance.

    I never noticed this before, could this be due to the extra air draw from the stage III? I fired it back up with the seats off and everything looked ok. My rear tray is out and the rear seat has been drilled out for extra air flow. Any suggestions?
    Last edited by Gus13letter; 06-22-2008 at 04:54 PM.


  2. #2
    AKA: Larry lafjax's Avatar
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    Quote Originally Posted by Gus13letter View Post
    I just installed an XS intercooler, Riva Stage III supercharger, 42Lb injectors, Riva catch can, and gutted my waterbox. I fired it up without the seats to make sure everything was ok. All looked ok. When I put both seats on and I reved it up, the seats seamed to be bouncing/fluttering like something was out of balance.

    I never noticed this before, could this be due to the extra air draw from the stage III? I fired it back up with the seats off and everything looked ok. My rear tray is out and the rear seat has been drilled out for extra air flow. Any suggestions?
    Geez, I don't know...My RXT is close to the same as yours. I've never noticed any seat fluttering but I really haven't paid attention to that. I think I would put it in the water and ride to see if you can pin it down closer. Something caught in your pump would cause the whole ski to fiberate and sound terrible. Maybe check the pump and drive shaft for crap. Be sure nothing leaks when you put it in the water before you take off on it.

  3. #3
    speedskixp's Avatar
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    I have seen this also. It is caused by the suction of the rr intake and the larger wheel.

  4. #4
    Gus13letter's Avatar
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    Yeah I never noticed it before. WHen idle its not too bad, but when I rev it up a little is when I really notice it. When the seats are off everything seems fine. I definately notice that the supercharger it louder.

    Time for some more air inlets.
    Last edited by Gus13letter; 06-20-2008 at 07:37 PM.

  5. #5
    The most interesting man in the world. Nils888's Avatar
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    Quote Originally Posted by Gus13letter View Post
    I just installed an XS intercooler, Riva Stage III supercharger, 42Lb injectors, Riva catch can, and gutted my waterbox. I fired it up without the seats to make sure everything was ok. All looked ok. When I put both seats on and I reved it up, the seats seamed to be bouncing/fluttering like something was out of balance.

    I never noticed this before, could this be due to the extra air draw from the stage III? I fired it back up with the seats off and everything looked ok. My rear tray is out and the rear seat has been drilled out for extra air flow. Any suggestions?
    This is normal for a modified supercharger. What you are seeing is air that the engine can not swallow at part throttle going backwards out the air intake

  6. #6
    Gus13letter's Avatar
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    Quote Originally Posted by Nils888 View Post
    This is normal for a modified supercharger. What you are seeing is air that the engine can not swallow at part throttle going backwards out the air intake
    So is adding a blow off vlave and or air vents a good idea? I had BOV before I added my new IC and SC.
    Last edited by Gus13letter; 06-21-2008 at 02:10 PM.

  7. #7
    Got Boost? psycho rxp's Avatar
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    Mine made the seat shutter the other day, when a coupler came off the SC. Big boost leak..lol

  8. #8
    Gus13letter's Avatar
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    Whole ski shudders bad with seats on.

    TTT
    Original post updated from my ride today.

    *** Update 6/22/08: ***
    Took it out today and I need some help please.
    With both seats on if the ski is given gas it shudders really bad!
    With the rear seat of it is noticable, but not so bad. I cecked everything even cutting the intercooler pipes to have a more free flow but same problem. Ski performs great other than the off throttle shudder. I need a new prop, 8200 RPMs (on the rev limiter) and 71.5 on the GPS.

    I must say I first noticed this when I flushed the ski for the first time.
    Could it be the way my waterbox it cut? When I removed it today to install the GH Shorty I noticed the waterbox was completely full even after reving it up.
    Last edited by Gus13letter; 06-22-2008 at 02:15 PM.

  9. #9
    My new toys at work bruinsrme's Avatar
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    Do you have any extra holes to allow more air to come into the hull?

  10. #10
    Gus13letter's Avatar
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    Quote Originally Posted by bruinsrme View Post
    Do you have any extra holes to allow more air to come into the hull?
    No I do not, but I know others that have the stage 3 and dont have additional holes.
    Seems odd that the whole ski would shudder like that due to lack of air though. Like a bad cavitation - weeds in impeller, but thats not the case.

    Could the waterbox have anything to do with it? See above post, it was full of water even after reving the engine, maybe choking the inlet pipe? I am getting the GH shorty this week. I am at a loss here.

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