Please HELP! -- 98 seadoo gtx ltd motor rebuild

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Double07

Double07

New Member
Hello everyone.
Frustrated newbie here.
I recently purchased a 98 gtx limited, took it out to the lake first time, and it ran ok at low speed but died at high speed after a few mins. I took it to the shop for a tune-up, and went back days later, but it happened again. I found out about the gray hose issue, so I pulled the carb, replaced all gaskets and valves, but FORGOT to clean the jets. The carb wasnt too dirty (probably been cleaned before). Third time out, the same thing happened again, only this time it wouldnt start back up after several attempts. Frustrated, I took it home, pulled the rave valves, and noticed that the valve surface on the side facing the cylinder looked like it was melted a little bit on the PTO side. I did a compression test and found out that the MAG cylinder is at 90psi while the PTO cylinder is at 50psi. I guess I am in trouble now. I am looking at rebuilding the motor myself to save some money.
so here are the questions.

1. How easy/hard is it to rebuild the 947 motor?
2. www.seadoo-parts.com have a top-end and crank rebuild kit for under $500. Are there other parts that I would need?
3. for the top end kit, there are different options for piston oversize how do I know what option to go with?
4. Are there any special tools that I would need to do this.

Sorry for too many questions. I just want to get a better assesment of what I am up against before diving in. I know there are lots of smart people on this forum, and I hope you can come to my rescue.
 
ebay...

hey double...thats a great price, only problem, and I believe, from what I remember, is the "oem" crank, the pin, that the rod surrounds, that connects the 2-journals, on each, is welded, so not only buying the kit, but need to have it ground/pushed out, then new ones installed, welded....

Used this company, a few times, and a great price...

http://cgi.ebay.com/ebaymotors/Sea-...30324843059QQptZPersonalQ5fWatercraftQ5fParts

WTF, did the mechanic, even do...while apart, sign up for "prem mem" for 1 month, cost 10 buks, then cancel after you've downloaded the manual for your ski....but use it, to go thru the carbs, clean/rebuild them, pay attention to the xcellerator pump and fittings, need to be cleared..

Just look'n at ur thread again, you can once jugs are off, look at/inspect the rods, for discolor and if none, and bearings at bottom, still feel smooth and tight tolerance at rod bearing, may be-able to get away with a "hone" and new pistons, along with gasket kit??
 
Thanks...
yeah. not sure what the mechanic did. he took 125 bucks for the tune up. and now he wants 2 grand for the rebuild.

Anyway, I do have the manual and the racing handbook as well.
I will pull the engine out today and see if I need to rebuild the crank also. is there any special tool needed in the rebuild process? if I can get away with hone and piston/rings/gasket, how can I determine what size of piston I need (standard or over). I will go with your recommendation on the parts.
Thanks for your help
 
"if your lucky", be- able to read the #, on top of any 1 of those pistons, if not, when you get it "honed", the machinist, will tell you.
Check out the "tag" on the magneto housing, it'll tell you, size of motor, bore and stroke of piston/rod...
 
hone or rebore?

Ok. I pulled out the motor, pulled off the head and cylinder block, and it looks like I had an oil problem. the cylinders looked very dry, but the dome looked ok. I noticed that part of the rings have been fused together with the piston, probably from friction.
I think the bore is a standard bore because the piston has written on it

010-819P
STD
AUS

I am guessing the STD means standard bore.
A couple of questions

1. How do you know when to hone or rebore? I ran my fingers through the inside of the cylider, and I could feel tiny grooves and ridges. nothing big, but then I dont know what it is suppose to look like.

2. when I turn the flywheel around, I here a rattling sound from inside the crank case when the crank shaft on the PTO side comes up. is this normal? or is it an indication that I need to rebuild the crank too?

Thanks for the help
 
You will have to bore it out. Take the engine completely apart. If it was starved for oil, replace or rebuild the crankshaft.

Chester
 
bendix cross reference??

I have everything pulled appart, cleaned and preped for reinstall. recuild kit should be comming in today.
I just found out that my Bendix (the idler gear assembly for the starter) has a couple of broken teeth. Some of the websites I checked have it cross-listed as a bendix for Yamaha Jestki with part number 6M6-8183E00-00. I can get it much cheaper as a Yamaha bendix than as a seadoo bendix. Does anyone know if the bendix is inerchangeable between the two makes? the pictures I have seen look dead-on identical.

I have a 98 GTX Limited.
Thanks
 
Double07 said:
I have everything pulled appart, cleaned and preped for reinstall. recuild kit should be comming in today.
I just found out that my Bendix (the idler gear assembly for the starter) has a couple of broken teeth. Some of the websites I checked have it cross-listed as a bendix for Yamaha Jestki with part number 6M6-8183E00-00. I can get it much cheaper as a Yamaha bendix than as a seadoo bendix. Does anyone know if the bendix is inerchangeable between the two makes? the pictures I have seen look dead-on identical.

I have a 98 GTX Limited.
Thanks
Click to expand...

Yes, the reduction gear is the same for Sea-Doo, Yamaha, Kawasaki, Polaris, and some Tigersharks.

Chester
 
First things first pull the carbs and check the internal filters... if the mechanic didn't clean them then you have a lean seize condition. a top end is all you will need to do. be careful pulling the piston pins out, the roller bearings in there are not caged and will fall down in the crank if not careful. Then you will be doing a complete rebuild.
 
bore size

Thanks guys for the help.
I got the new crank and piston today, took it over to a machine shop, and I was told that reboring to one over (.25mm) will not be enough to clean up the cylinder. looks like I have to return the piston and get a second size over.
from the shop manual, it looks like 2 sizes over will exceed teh recommended clearance between the RAVE valve and the cylinder. What do I do now? can I still go with 2 sizes over? or do I have to get a new sleeve/cylinder block? if I go with 2 sizes over, what do I need to do to stay within the recommendation on the clearance between RAVE valve and piston?
Help please... am lost.
 
You can go 2nd oversize if you have your machinist shave the RAVE valves by .005".

Chester
 
How much do you think you will have with machine work and parts? My suggestion would be to send everything back and order a Sbt engine with a 2 year warranty for around $1200.
 
SBT has the silver premium engine for $1495. shipping on the rebuilt and core probably adds another $100.
I spent around $650 on engine rebuild kit including shipping. probably another $50 on miscelenous expenses. The rebore is $50 a cylinder here in sacramento. If I can save $700 to $800, I think its worth it. The experience too is good to have.
 
Runaway after rebuild...

I had an engine runaway (dieseling) after top and bottom end rebuild. I have to say that I was scared shitless as I have never seen or heard anything like this hapenning on a gasoline motor ever. I thought I had lost my mind when after I pulled the lanyard and the spark plug wires, and it was still running like a bat out of hell. :confused:

It was scary because I had bypassed my fuel selector switch, and I didnt know how to shut it off. I ended up pinching the fuel line and holding tight untill the motor died. This happened twice and I am not sure if I messed anything up by doing this.

I have read a few posts on runaway in this forum, and I am trying to find out why mine is happening. I read that carbon deposits in cylinder and lean fuel/air mixture are most common causes.
I dont have any deposit in this case since this is a new top/bottom end. I also cleaned out and completely rebuilt the carb and replaced all gaskets.
What else can cause this? I am premixing now, and I think I have a bit more oil in the premix (30:1) I heard you should use more oil during break in.
Can too much oil in premix cause runaway?
 
as far as I know you should be running 40:1 not 30:1....that would have caused a lean condition....and caused the motor to run away on a trailer according to what I have heard
 
and seriously, why would you bypass your fuel selector? it is a safty device there for a reason...if it is bad then replace it.
 
you did it twice? for how long did it go on for and how high of rpms? should be carefull before you have to rebuild it again.
 
Sea-Doo uses the following ratio:

40 to 1 ratio oil to fuel ratio or 3.2 ounces to a gallon.



you just created your own lean condition
 
runaway after rebuild

yeah I was being too cautious... guess it feels stupid now. :stupid:
I know 40:1 is the right premix ratio, but I read somewhere on this forum that it is a good idea to use more oil during run-in after rebuild.
I bought a new fuel selector line, but later decided to bypass it because I heard that it can get too dirty and obstruct fuel delivery to carb causing lean condition, so I just decidednot to use it. I will have it reconnected.

It happened twice. After the first time, I thought I had the idle too high, so I backed all the way off on the idle screw and started it the seccond time. in both cases, I never gave it gas. it just idled for a few seconds, with the rev increasing slowly until it hit around 4500 RPM, then it quickly went to around 6800 rpm.
It lasted for about 90 seconds in both cases. that's how long it took to die after I pinched the fuel line. Could I have damaged something in the motor? Is there anything else I need to check before attempting to start it again? I will dump the current fuel and redo a 40:1 premix
 
forgive me for thinking backwards, you where running more oil, I sometimes get it confused like wiring sizes. Having more oil in it should not have hurt it.
 
check for air leaks around the carbs and intake manifolds, if a large enough leak is there it would raise the idle and possibly could have run off?
 
Finanly got it right!

:hurray:
I dumped the old fuel and made exactly 40:1 premix, and I also pulled the carb out and applied sealant to the gaskets. Man, that head pipe is a &!+@# to get on. I started on the trailer, and it reved up to 3K without running away. I even gave it a little gas and it didnt run away.

I took it to the lake yesterday, oh man, that baby flew. I could even feel the power valves kick in onve it revs over 4K, and it jumps like someone gave it a kick in the @$$. I made fast runs, slow runs, pulled up by the dock, and everything looked good under the hood.

I couldnt be happier. THANKS SO MUCH to everyone for your help. This is a great community.:cheers:
Now that I have it up and running, is there anything I need to watch out for? any maintenance tips? I love the fact that I rebuilt the motor and learnt a lot, but I really wouldnt like to go through it again anytime soon. I am currently premixing, already replaced fuel lines, rebuilt carb with new filter. I havent done anything on the jet pump yet.
Thanks again guys, and any advice or tips to help me keep her running smoothly will be appreciated.
 
90 seconds is a long time for a runaway condition, I've seen motors cooked in about that much time. in the future, all you have to do is pull the choke and it will stop the motor, no air = no run.
 
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