650/X-2 650sx vibrations at 1/2- full throttle

W

waterbox

Location
California
Getting some weird vibes on my 650sx, trying to track down the problem. Motor mounts are good, driveshaft is straight. My grate had a small casting burr along both inner edges (2 bar), so I filed it out and polished it, also the grate and ride plate were not siliconed together, so I siliconed them, thinking it could cause cavitation? My impeller has no vertical play, and the driveshaft bearing feels tight, but the driveshaft does slide in and out of it fairly easliy, so could that be an issue? Next I'm going to check coupler alignment, to see if I need to shim the motor. Any other ideas? thanks guys :brap:
 
Snivilous

Snivilous

Location
SW UT
I'm assuming you checked the impeller isn't missing any pieces? I've never heard of anyone doing it, but you could balance your impeller. Every other major rotating part for mechanical applications get's balanced a lot, and often, to make sure you get no vibration what so ever (tires, propellers, turbine blades, fans, etc.) Same general application.

If you have a newer impeller it's probably already balanced at the factory.
 
W

waterbox

Location
California
El Joker said:
Stock impeller and pump combo sometimes cause vibrations.
Click to expand...

thanks guys, yes it has the stock pos impeller, but its actually in pretty decent shape, no missing pieces, has a few very tiny imperfections, but it's not as bad as my buddies, and his is way worse. It's a weird vibe, its not a "smooth" vibration, I mean if I hold it at like 1/2 throttle, the vibration kinda goes in and out, but never goes away. And it ONLY DOES IT IN THE WATER. Does that help?

Is the driveshaft supposed to slide thru the shaft bearing easily? Or is it a tight fit?
 
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Snivilous

Snivilous

Location
SW UT
My drive shaft slid right out piece of cake (haven't put it back in yet). The fact it only happens it water, makes me think it's from the water flow hitting it's equivalent of a first mode and starting to wobble from some issue in your pump. Obviously out of the water your RPM would be faster, and besides no water nothing else would change so that removes the balance question. How "bad" is your impeller? My stock impeller was essentially perfect with some scraps on it, and front edges dinged. Does yours have any area that would cause the water flow to act weird? Pump cone maybe? Or any other odd variation in the whole area the water goes through?
 
W

waterbox

Location
California
The only thing I could find that would be an issue is that nothing was siliconed under the pump. Would that make anything vibrate? Thanks for you help dude
 
Snivilous

Snivilous

Location
SW UT
If everything is torqued down it shouldn't. I don't know the exact answer to why you silicone the pump in, I suspect it's to stop vibration and also have a slight disconnect from the hull to the pump so it doesn't rattle around and destroy the nearby fiberglass. I wouldn't worry about siliconing the intake grate, mostly the pump assembly. How bad of a vibration is it? And did this just start, or has it been like this since you got it?
 
W

waterbox

Location
California
El Joker said:
Im pretty sure the reason why you silicone the pump area is to reduce the risk of cavitation.
Click to expand...

Thats what I was thinking... I siliconed where the grate meets the pump...


And its been doing it since I bought it, I picked it up last summer for $750, rode it 3 times last summer. I was hoping to get it figured out before this summer because it's annoying as hell. Its not a TERRIBLE vibe, but I can definitely feel it in the tray. I wanna get it dialed so I can start putting some upgrades on it. It Already has a 2 bar grate, PJS ride plate, Zero degree bars, And I added a pole limiting rope, and oil injection block off.
If I pin it hard out of the hole I don't notice the vibrations as much, its mainly when I'm cruising.
 
Snivilous

Snivilous

Location
SW UT
waterbox said:

I'll check the alignment for sure, is it more likely the midshaft bearing of the pump bearings? I mean is one known to go out more often?
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I don't know stats on them going out, but I would just feel them out. See if the driveshaft slides in nicely, doesn't have much play, and feel if the bearing slides easily or catches anywhere. Likewise with the pump.
 
N2 H2O

N2 H2O

Previously Tbone550
Location
Charlotte, NC
The vibration you are feeling is most likely cavitiation. You need to silicone all the way around between the pump shoe and the hull. If not, the pump sucks air from the area around the pump. Cavitation causes a bad vibration. The kawasaki driveshafts don't have to be absolutely perfectly aligned because of the free floating bearing. Most kawasakis do have a vibration at idle no matter what because the splines that slide into the pump or loose, but the vibration should go away when you give it throttle. The only other thing I can think of is if the pump bearings are bad. Take the pump out and make sure the impeller clearance is good all the way around and make sure the pump spins freely.
 
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W

waterbox

Location
California
Thanks for the help N2. So Last weekend, we had about a 70 degree day, so I decided it was time to take the ski out. Water Temp was a nipple stiffening 48 degrees. I have never used a wetsuit before, but after my friend loaned my one, I figured I'd give it a try. Possibly the best invention ever! Anyway, after removing all the casting burs from the grate, and siliconing everything, I was hoping things would be smoother. Not the case, she still vibrates pretty rough. If I hold it wide open on flat water, it vibes pretty hard, but I notice that when I let off the throttle after being pinned, and roll back onto the gas, you can REALLY feel it, which leads me to think the pump needs to be rebuilt? you can definitely feel it in the tray, so I'm hoping a pump rebuild kit fixes it. I'll probably put an impeller on it while I'm in there, just in case my prop is bad.

folsomski.jpg
 
849tigerbotkv1

849tigerbotkv1

formerly ihate5mphzone
Location
where i can ride 2stroke
I dont think its your pump imho its probably your driveshaft is bend or something . but try to rebuild your pump and go from there and if its still vibrating i have a extra driveshaft here i can sell you
 
W

waterbox

Location
California
ihate5mphzone said:
I dont think its your pump imho its probably your driveshaft is bend or something . but try to rebuild your pump and go from there and if its still vibrating i have a extra driveshaft here i can sell you
Click to expand...

I have climbed underneath the ski on my stand and had my brother rev the motor, and there are no visible vibes on the driveshaft, It looks as though its not even spinning, so I feel that its pretty straight. What if the splines on the impeller are worn, would that cause it?
 
W

waterbox

Location
California
Hey guys, I had a chance to tear down my ski completely yesterday. To my suprise the pump bearings are smooth as silk, no play at all. I did however, find a torn motor mount. Either I overlooked it last time I pulled the motor, Or I tore it on the last ride. After getting the pump out though, I also found some nasty pitting on the inside of the impeller blades. Could this be causing the vibes and thats what caused the torn motor mount? or was it more likely it was the motor mount the whole time? Wither way, I'm putting a stainless one in now that its apart...
120427_0003.jpg
 
Snivilous

Snivilous

Location
SW UT
Motor mount the whole time. That's nothing for a stock impeller and wouldn't even be noticed when riding.
 
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