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1997 GTI Vibration

etemplet

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1996 SPI, 1996 GTX, 1997 GTX
Going back to the beginning of summer this ski was great after I made a whole lot of tweaks that is. Immediately the owner sunk the ski... and in the process of trying to start it sheared the starter shaft. I was able to get the ski fixed up and operational. Later on, the ski came back with the exhaust manifold broken bolts and 2 failed motor mount bolts. I pulled the pump and aligned everything. A month or so later the ski again came in with water in the electrical box so I assume it dang near sank again. This ski plus one more have been through hell over the summer and.... I wish I truly knew how many hours they put on them. Non-Stop riding that is sure. LOL Concerning the vibration...I'm wondering if the engine vibration is the result of a bent connecting rod from the locked up engine and broken starter shaft. I never did a compression check since the initial 150psi on both cylinders. I'm thinking it's gonna need a crank. Thoughts??
 
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AKnarrowback

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Fairbanks Alaska
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94 xp
94 sp
94 gtx
Index TDC of each piston onto the pto flywheel and see if the two mark's are 180 out from each other. Double check the drive shaft in a lathe to see if it's bent.

I had a twisted crank on a 96 Ultra (sled) that started and ran fine down low, but it fought itself at different rpm's so the over all running was terrible. A vibration would, in theory, be caused by an odd firing and not a change in rotating mass if a rod is bent.

I know you know your stuff on these rigs so I'm interested to hear what you find.
 

mikidymac

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I’ve actually never heard of one having a bent rod. If it’s full of water the starter won’t crank it over. They can throw a rod though.
 

etemplet

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1996 SPI, 1996 GTX, 1997 GTX
Ski has been running all summer. Just has vibration. He filled the freakin thing up with water, then broke the starter. Then the flipped it again a few months later and filled it with water again and BENT the starter shaft. Maybe the engine bearings are going out. :) Some people shouldn't own jet skis. LOL

Good call on the drive shaft I"ll give it a look.
 

etemplet

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1996 SPI, 1996 GTX, 1997 GTX
I got a couple of 717's to build and I'm counting this as one. Should be less work compared to the 787's.
 

AKnarrowback

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554
Location
Fairbanks Alaska
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94 xp
94 sp
94 gtx
Have seen a bent rod on a 580 one time. The crank would turn 270+/- degrees but the rod would contact the crank and stop the whole thing. Both ends were still in line and parallel, the rod had three bends giving it a knee half way between the two. The customer said they had rolled over, righted it, hit the starter, it ran for a split second and locked up.
 

GGuillot

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Alabama
Water Crafts
1997 GTX
1996 GSX
A bent driveshaft will allow water in at the carbon seal, which could be how it keeps getting water in the hull. Back in the Summer I chased this problem for awhile on the GTX, new carbon seal, rechecked alignment didn't do a thing. Take the driveshaft out and roll it on a flat surface to check.
 

etemplet

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Location
Louisiana
Water Crafts
1996 SPI, 1996 GTX, 1997 GTX
Have seen a bent rod on a 580 one time. The crank would turn 270+/- degrees but the rod would contact the crank and stop the whole thing. Both ends were still in line and parallel, the rod had three bends giving it a knee half way between the two. The customer said they had rolled over, righted it, hit the starter, it ran for a split second and locked up.
I was thinking of a mildly bent rod that prevented the piston from going to TDC causing lopsided compression as the root cause of the vibration. I believe the vibration is coming from the engine but I'd sure be happy if it was't. LOL Great input !!! I am beginning to think that after a ski rolls over starting shouldn't be attempted without first pulling the spark plugs. That's how $hiznit gets bent and broke. :)
 

etemplet

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2,901
Location
Louisiana
Water Crafts
1996 SPI, 1996 GTX, 1997 GTX
I figured I'd piggy back this failure along with the GTI. This is a 717 GS 1998. I know the history of the ski. Abused as much as one could expect. Lots of inexperienced riders and 100% throttle most of the time. I doubt they ever properly warned the engine before going wide open. I'm curious if running fatter on the high speeds would help this piston damage. PTO Con rode bearing failed. Lots of even wear on the rotary valve outboard plate, no wear on the engine side. Thoughts?? (ski started and ran well till it seized)1998 GS Engine Rebuilt 717 (3).JPEG1998 GS Engine Rebuilt 717 (4).JPEG1998 GS engine Piston.JPG1998 GS engine Piston.JPEG
 
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mikidymac

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1996 XP
1996 HX
1991 Superjet
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With all the carbon between and below the rings I would say it's just worn out. When hot gasses get past the worn rings it burns off the oil film between the piston and cylinder and you get the seizing like on your lower piston skirt.
 
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etemplet

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Water Crafts
1996 SPI, 1996 GTX, 1997 GTX
Cylinder measurements were pretty darn good. I'm going .5 over. This was a sweet running ski and it will be again.
 
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etemplet

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1996 SPI, 1996 GTX, 1997 GTX
I didn't measure the pistons yet. I'll check them and post. Why do you ask?
 

etemplet

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2,901
Location
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1996 SPI, 1996 GTX, 1997 GTX
Oh well, I decided to do the engine myself. By the time I disassemble for shipping and package the engine, I can pull a few bolts and have it completely apart. This is my first 717 engine to do a complete overhaul. I usually just do the top end. This one however... needs a crank. :) I can't figure how to post a video so here are a few pictures.

Cylinder boring lathe.JPEGCylinder boring in lathe still picture.JPEGCylinders bored.JPG
 

etemplet

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2,901
Location
Louisiana
Water Crafts
1996 SPI, 1996 GTX, 1997 GTX
Gettin it cleaned up. I guess this is the alignment mark to time the stator. I made my own marks just in case. :)

GS 717 Engine Block Assembly (1).JPEGGS 717 Engine Block Assembly (2).JPEG
 

etemplet

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Messages
2,901
Location
Louisiana
Water Crafts
1996 SPI, 1996 GTX, 1997 GTX
What was the piston to cylinder clearance?

Chester
3.2235" 2.224" Piston skirt OD (New piston measures 3.2258")
3.331 on the cylinder bores.
Ring gap wasn't too bad at all.
I went .5mm over. :)
 

etemplet

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2,901
Location
Louisiana
Water Crafts
1996 SPI, 1996 GTX, 1997 GTX
It's alive !!! This baby is going in the water this week !!
 

GGuillot

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Messages
973
Location
Alabama
Water Crafts
1997 GTX
1996 GSX
It's alive !!! This baby is going in the water this week !!
This thread is a little confusing, what did you do to resolve the vibration issue on the 97' GTI? or was this the issue all along with the 98' GS?
 

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