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  1. #1

    2001 GP1200R Major vibrations

    I was going along, minding my own having a blast for about an hour on this ski with the following appropriate modifications:

    2001 GP1200R
    Riva intake grate
    Riva pump seal kit
    71 original hours

    When all of a sudden at about 15mph it was like the jet pump lost a bearing. The vibration was pretty massive at anything more than about 1/8 throttle, so I idled it back to the dock. Pulled it out, looked in the tail and found nothing obvious. Drove it home, proceeded with my normal after-lake procedure of washing and flushing. WHile flushing, I noticed the rear of the engine had a vibration good enough to make it shake under slight rev - the bottom end of #3 cyl. It shooke soo much/hard that it looked like the motor mounts were gonna come on loose. I'd say the engine had 1/4 or vibration/travel. I whipped out an AutoZone compression gauge and measured ~97psi on all three. Plugs look a little rich but I'm perfectly happy with that. I am not positive the comp gauge is accurate, and also I did not disable powervalve for the test. I think the engine is OK, it sounds good at idle it just shakes - or rather something is causing it to shake madly.

    I pulled the battery box and also the top cover for the jet drive input shaft. Everything really looks to be OK from inside the hull.
    Outside, the prop looks brand new from both front and rear. I did not yet remove the intake grate because one - nothing really popping out at me, and 2 - dont want to risk spinning the bolts in the hull.

    One thing I've noticed since I've owned this ski it - the jet drive sounds 'loose' out of the water when running. Its always done this and sounds no different now. I think it's normal but have not heard another waverunner like mine run out of water.

    So, what could be causing this? Please help!

  2. #2
    97 psi on 3 pistons is real low..............120 and higher is good....

  3. #3
    Its been at 95~100 psi since i bought it at 55 hours. Its been running fast and strong for the past 15 hours without problems. I dont second guess the low compression but nothing in the combustion chamber has changed. The compression gauge which I am using may be deceiving; its got a very short thread and only screws in 4 turns. Where the spark plugs screw in about a dozen turns; I think this gauge is not taking as much combustion space as another may.

  4. #4
    KamikazeGPR's Avatar
    Join Date
    Mar 2007
    i'm going to put my $$$ on a stick or piece of trash stuck between your impeller & wear ring. crawl under your trailer and shine a flashlight into pump tunnel. It's not easy to look 360 degrees around the wear ring. you may have to remove intake grate and feel with your hands. If your grate is sealed. It's much easier to remove pump since you don't have all the reverse crap to remove first. just 4 bolts.

    my first ride of this season with new impeller and wear ring. 200ft from ramp I sucked up something after running over a pile of leaves and sticks. heavy vibration and 5mph limp back to ramp. Had a 2" long x 1" wide x 1" thick piece of wood stuck on one of my impeller blades. removed intake grate, reached in and pulled it off.

  5. #5
    Well now I'm stumped. I started it again on the hose and the problem seems to have stopped for now. The impeller and wear ring look alright. I shined a flashlight into the pump and really cant see anything. I had a friend carefully turn the engine over by hand and everything looks shine and new for a 12 year old ski. I wish it was on a lake to test again right now.

    On the 95~100 psi compression - well, considering this vibration happened I decided to take the head off. The pistons, head, and walls look fine. I can see hone marks on the cylinder walls. I do not know if this motor was ever redone.

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