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1999 GSX Engine Blew-what could have caused it? Pics

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Seadoo99

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#1
Well after only 5 weeks of owning our 1999 GSX, it decided to let go. The motor just quit and would not turn over. I took out the motor today and there is a nice hole in the case. The counterbalance shaft is broke. The gear on the crank that drives the counterbalance shaft is all chewed up and shot. What could have caused this? What would you do? Buy the parts needed and put it back together. Buy a rebuilt short block or long block? If so, where is a good place to buy one? I am really new to the PWC's but am mechanically inclined. All help is appreciated.

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Dr Honda

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#2
OK.... here's what happened....


You lost the oil out of the counter weight. That cause the bearing to fail. When that happened, the weight shifted, and blew the engine case. When that happened... it tried to stop, but the engine was still spinning, and that broke the shaft, and stopped the gear.

Sorry for the loss... but thanks for sharing the pics.
 

Seadoo99

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#3
OK.... here's what happened....


You lost the oil out of the counter weight. That cause the bearing to fail. When that happened, the weight shifted, and blew the engine case. When that happened... it tried to stop, but the engine was still spinning, and that broke the shaft, and stopped the gear.

Sorry for the loss... but thanks for sharing the pics.
Ok, why did I lose the oil out of the counterweight? Is it oiled from the oil/gas mix or is it internal oil? Sorry but I am really new to this.
 

bighvygsx

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There should be 2 big hoses one going in under rotary valve and the one coming out other side of engine the both come from the oil tank and submerg the gears in oil. The same oil the engine Burns in the cylinders. The line may have got clogged. And the bottom end ran dry
 

Seadoo99

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There should be 2 big hoses one going in under rotary valve and the one coming out other side of engine the both come from the oil tank and submerg the gears in oil. The same oil the engine Burns in the cylinders. The line may have got clogged. And the bottom end ran dry
I believe if I read the above link correctly, the oil is actually sealed in the counterbalance shaft area. There is a little reservoir that holds the oil. I guess I am still unsure how the oil came out or was lost. Maybe the ski had been flipped prior to me owning it.
 
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#7
What would you do? Buy the parts needed and put it back together. Buy a rebuilt short block or long block? If so, where is a good place to buy one? I am really new to the PWC's but am mechanically inclined. All help is appreciated.
The problem you are going to find with most of the places you buy rebuilt engines is that they require a core (your old engine) to exchange for the one you are buying. Since your old one looks to be shot, you will have to pay a much higher price, or they may not want to do business with you at all. The places I am talking about are SBT, Fullbore, and SES to name a few.

You best bet may to to pickup a used engine on eBay or by purchasing a cheap running ski or an even cheaper non-running ski to swap the engine out. You may get a real good deal on a dead engine, maybe one just needing a top end done on it. You can then swap/rebuild parts as needed. Check your local craigslist as well, season is coming to an end soon and skis will be cheaper.
 

bighvygsx

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#8
The big line that was connected to engine under the air breather side. Did oil come pouring out of it when u disconnected it from the engine
 

manolocross

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#9
Thanx for sharing the pics...they are great for others to see and learn...SORRY for your loss :(...its a great ski and with proper repairs and replacement it can live again!!! GOOD LUCK!
 
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#10
There should be 2 big hoses one going in under rotary valve and the one coming out other side of engine the both come from the oil tank and submerg the gears in oil. The same oil the engine Burns in the cylinders. The line may have got clogged. And the bottom end ran dry
Yeah, he is not exactly correct here. Your problem was with the counterbalance gears. The oil coming from the oil tank, the 2 stroke oil, is used in the lower end for the rotary valve gears, not the counterbalance gears. And, this is only the case for rotary engines and the 951 you have is a reed valve engine, so this does not apply.

I believe if I read the above link correctly, the oil is actually sealed in the counterbalance shaft area. There is a little reservoir that holds the oil. I guess I am still unsure how the oil came out or was lost. Maybe the ski had been flipped prior to me owning it.
It is pretty isolated in the lower end, but it is not completely sealed off. That is why when the engine is submerged, you get water in the counterbalance chamber too.

And yes, it being flipped or submerged prior to you buying it could have gotten water in the counterbalance area and fouled the oil. If you look at the pic of the oil I took out in that link I posted, you can see how bad it looks. It wasn't even oil, it was just dirty black water. Had I not changed it, I may have ended up with an engine that looks much like yours.

It is also possible at some point the lower end was opened and when reassembling, it was never filled. You just never know when it comes to a used ski.
 
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Seadoo99

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#11
The big line that was connected to engine under the air breather side. Did oil come pouring out of it when u disconnected it from the engine
Only oil line that I saw comes from the oil tank and goes to the oil injection unit on the front of the motor. It then goes to each carb to squirt oil in. The counterbalance has it's own oil reservoir.
 
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#12
Only oil line that I saw comes from the oil tank and goes to the oil injection unit on the front of the motor. It then goes to each carb to squirt oil in. The counterbalance has it's own oil reservoir.
You are seeing things correctly, bighvygsx obviously has a 787/800 rotary valve motor. You have the 947/951 engine (yours being a Limited model), which does not have a rotary valve.
 

Seadoo99

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#13
You are seeing things correctly, bighvygsx obviously has a 787/800 rotary valve motor. You have the 947/951 engine (yours being a Limited model), which does not have a rotary valve.
Thanks for clearing that up for me. I went out again and looked and only saw the one.

As far as the motor, I am looking for a motor to rebuild. As you have stated, most want a core for exchange. I might look for a cheap core that can be exchanged. I am not in a big hurry as it is close to the end of the season anyway.

Thanks for all the help everyone!!
 

Dr Honda

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#15
There should be 2 big hoses one going in under rotary valve and the one coming out other side of engine the both come from the oil tank and submerg the gears in oil. The same oil the engine Burns in the cylinders. The line may have got clogged. And the bottom end ran dry
The 951 engine is a reed valve engine. (no hoses, and no rotary valve)




****EDIT*****

Someone already said it. Sorry.
 

bigJake

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#16
dj, great write up. I have stupid question. It sounds like the Counterbalance is pretty well sealed, how exactly (what path) does the water get into the Counterbalance? Also, if the ski floods, I assume it is necessary to drain the oil from the lower end as well? I'm specifically interested in the 787. Thanks.
 
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#17
dj, great write up. I have stupid question. It sounds like the Counterbalance is pretty well sealed, how exactly (what path) does the water get into the Counterbalance? Also, if the ski floods, I assume it is necessary to drain the oil from the lower end as well? I'm specifically interested in the 787. Thanks.
There is a small hole on the inside of the engine that is used to fill the reservoir when assembling (at least on pre '97 motors). But the gears themselves are surrounded by small gaps of air so they can move freely. This would likely account for most of the water penetration.

The counterbalance oil just sits at the bottom of the chamber and as the gear spins it gets continuously coated in oil. The chamber is designed to hold the oil even if upside down as well as when you flip your ski over (as long as you flip it in the direction your rear sticker tells you).

But if the ski floods, you should check this reservoir just to be sure your oil is good. If not, you should change it. This sucks for the pre '97 engine, as you do not have easy access at all. One option you have is to drill and tap a hole in any 787/800 engine without it, but who wants to do this unless your engine is already out.

They definitely saw the need for it in the later engines, but... to put those at ease who are thinking right now "oh shite!"...we hear a lot around here about engines flooding but very little of holes being blown out of crankcases. It would seem to me that the severe damage is a more unlikely scenario. And I would bet that less than 10% of those people are changing their counterbalance oil.
 

bigJake

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#18
There is a small hole on the inside of the engine that is used to fill the reservoir when assembling (at least on pre '97 motors). But the gears themselves are surrounded by small gaps of air so they can move freely. This would likely account for most of the water penetration.

The counterbalance oil just sits at the bottom of the chamber and as the gear spins it gets continuously coated in oil. The chamber is designed to hold the oil even if upside down as well as when you flip your ski over (as long as you flip it in the direction your rear sticker tells you).

But if the ski floods, you should check this reservoir just to be sure your oil is good. If not, you should change it. This sucks for the pre '97 engine, as you do not have easy access at all. One option you have is to drill and tap a hole in any 787/800 engine without it, but who wants to do this unless your engine is already out.

They definitely saw the need for it in the later engines, but... to put those at ease who are thinking right now "oh shite!"...we hear a lot around here about engines flooding but very little of holes being blown out of crankcases. It would seem to me that the severe damage is a more unlikely scenario. And I would bet that less than 10% of those people are changing their counterbalance oil.
thanks :cheers:[
 
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#20
So how much oil is supposed to be in the counter balancer area
That depends on the engine. The link I posted for the changing procedure lists the amount for each engine, but without looking at it, I believe it is 40mL for the 947/951 and 30mL for the 787/800.
 

Dr Honda

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#21
That depends on the engine. The link I posted for the changing procedure lists the amount for each engine, but without looking at it, I believe it is 40mL for the 947/951 and 30mL for the 787/800.
Yep... 1oz for the 800 and 1.35oz for the 951.
 

bighvygsx

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#22
That's what I thought. 1oz isn't very much. Also I was wondering if u can use the 2 stroke xp-s oil. It maintains my RV gears?
 
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#23
That's what I thought. 1oz isn't very much. Also I was wondering if u can use the 2 stroke xp-s oil. It maintains my RV gears?
Well, in '96, the assembly instructions had you putting injection oil in the counterbalance chamber but they changed the requirement in '97 to SAE 30 oil. It's not like buying a quart of SAE 30 is difficult or expensive, so I would go with that. They made the switch to that type of oil because I assume they found it protected the gears better.
 
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#24
dj, great write up. I have stupid question. It sounds like the Counterbalance is pretty well sealed, how exactly (what path) does the water get into the Counterbalance? Also, if the ski floods, I assume it is necessary to drain the oil from the lower end as well? I'm specifically interested in the 787. Thanks.
There is a small hole on the inside of the engine that is used to fill the reservoir when assembling (at least on pre '97 motors). But the gears themselves are surrounded by small gaps of air so they can move freely. This would likely account for most of the water penetration.
To further what I said here, my best guess when the engine is submerged is through the air intake, through carbs, into cylinders, and then into the lower case. Once in the lower end, water may seep past the seals/bearings and into the different chambers.
 
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