1997 GTX 787 WOT at Startup

[BoaterCycle123]

Hello,

This site has been extremely helpful and I am grateful for everything everyone has shared with me thus far. I wanted to address another issue that I am having with the carbs. Just a little history on the machine. I bought the machine with a rusted crank and have rebuilt the motor from the ground up.

After that rebuild, I started the engine (After some spark timing issue, in another thread) and the second that it starts, it revved to around 4000rpm right off the bat. The only thing that slowed it was pulling the choke.

So naturally, my first move was re-build the carbs. I completed that and now it Revs right up to Max RPM as soon as it starts. So the carb cleaning worked as it is revving higher than before! Perfect! However, this still does not fix why it is stuck at WOT (wide open throttle). The only parts that I did not mess with on the carbs were the High-end and low-end screws. I am going to take my best shot at those tonight to see what the issue is. It does not like like anything is missing from the carbs compared to the carb cleaning how-to. I did not check the pop off pressures either. they seem to be getting plenty of fuel though.

I have done an oil pump bypass, could an air leak after the carb cause this? I plugged the old brass nipples with Marine JBWeld.

I have also checked the throttle cables and everything related to the throttle and it is all operating well.

Anyone had this issue or know what the fix maybe?

TIA

 

[AKnarrowback]

Reving to 4000 out of the water is not a bad thing, in my opinion. Put it in the water and that 4000 goes down quite a bit. Reving higher after a carb rebuild tells me the throttle cable or idle setting is wrong causing the carbs to open too far at idle. Look inside the carbs with the engine shut off, is the butterfly valve closing all the way? Out of the water a motor can rev very high with a little throttle opening, no resistance equals free reving.

 

[BoaterCycle123]

Reving to 4000 out of the water is not a bad thing, in my opinion. Put it in the water and that 4000 goes down quite a bit. Reving higher after a carb rebuild tells me the throttle cable or idle setting is wrong causing the carbs to open too far at idle.

My other identical ski that I bought with it did not require a rebuild. It only revs to about 2400. And the throttle works correctly on it.

I have the low idle screw turned down (out) a lot. And when I throttle this one it doesnt do anything.

 

[mikidymac]

You have an air leak causing a runaway ski.
You should have pressure tested the engine before installing it. It could be crank seals, base gaskets, intake o-ring and gaskets, carb base gaskets.

Also there is no reason to block off the oil injection on these and if you for some strange reason still have to get the kit with the plate and nipple covers. Never use JB Weld.

This is not a carb issue especially if you have the idle backed all the way out.

 

[BoaterCycle123]

You have an air leak causing a runaway ski.
You should have pressure tested the engine before installing it. It could be crank seals, base gaskets, intake o-ring and gaskets, carb base gaskets.

Also there is no reason to block off the oil injection on these and if you for some strange reason still have to get the kit with the plate and nipple covers. Never use JB Weld.

This is not a carb issue especially if you have the idle backed all the way out.

Very good information! How would I pressure test the crank case?

I thought all these oil injection pumps were notorious for failing and causing fatal engine failures?

 

[mikidymac]

Very good information! How would I pressure test the crank case?

I thought all these oil injection pumps were notorious for failing and causing fatal engine failures?

That is a very common misconception. Whenever an engine goes everyone always blames the oil injection. The seadoo system is extremely reliable and only has two common failure points.
1. Using the wrong oil, Seadoo requires API-TC oil, never TCW-3 outboard, If it is blue or green it's wrong.
2. THe small 3/32" oil lines from the pump to the intake get brittle after 20 years and should be replaced.

To pressure test the engine you have to block off the cylinder to exhaust manifold and intake to carb joints then pump 8 psi of air into the pulse nipple fitting. It should hold 8 pis for an absolute minimum of 10 minutes but indefinitely is better. This needs to be done with any engine that has been apart or new or more than 20 years old.

 

[BoaterCycle123]

That is a very common misconception. Whenever an engine goes everyone always blames the oil injection. The seadoo system is extremely reliable and only has two common failure points.
1. Using the wrong oil, Seadoo requires API-TC oil, never TCW-3 outboard, If it is blue or green it's wrong.
2. THe small 3/32" oil lines from the pump to the intake get brittle after 20 years and should be replaced.

To pressure test the engine you have to block off the cylinder to exhaust manifold and intake to carb joints then pump 8 psi of air into the pulse nipple fitting. It should hold 8 pis for an absolute minimum of 10 minutes but indefinitely is better. This needs to be done with any engine that has been apart or new or more than 20 years old.

Miki,

This is good. I'll probably pull the engine and try to test it soon.

This may be a good time to ask why the gasket kit came with 3 gasket that go between the crank and the jugs?

Is there an engine rebuild.how to on here to see if I missed something?

 

[GGuillot]

Hello,

This site has been extremely helpful and I am grateful for everything everyone has shared with me thus far. I wanted to address another issue that I am having with the carbs. Just a little history on the machine. I bought the machine with a rusted crank and have rebuilt the motor from the ground up.

After that rebuild, I started the engine (After some spark timing issue, in another thread) and the second that it starts, it revved to around 4000rpm right off the bat. The only thing that slowed it was pulling the choke.

So naturally, my first move was re-build the carbs. I completed that and now it Revs right up to Max RPM as soon as it starts. So the carb cleaning worked as it is revving higher than before! Perfect! However, this still does not fix why it is stuck at WOT (wide open throttle). The only parts that I did not mess with on the carbs were the High-end and low-end screws. I am going to take my best shot at those tonight to see what the issue is. It does not like like anything is missing from the carbs compared to the carb cleaning how-to. I did not check the pop off pressures either. they seem to be getting plenty of fuel though.

I have done an oil pump bypass, could an air leak after the carb cause this? I plugged the old brass nipples with Marine JBWeld.

I have also checked the throttle cables and everything related to the throttle and it is all operating well.

Anyone had this issue or know what the fix maybe?

TIA

Sounds like a big vacuum leak if the throttle plates are closed and it's revving to the moon. Couple questions, please forgive me if it's too obvious or insulting.

On the front (mag) and rear (pto) seals are in, new, and undamaged? pto flywheel is installed? mag cover with seal bolted to cases when you installed and were careful not to pinch that seal? Case halves were mated using a good sealant? ie, loctite 518, three bond, etc. Rotary valve cover has an oring? new carb base gaskets? oring on balance shaft case cap? balance shaft fill and drain screws/cap in? pulse line case to carb tight?

Just throwing things out there on a rebuild I know need attention on the 787, I rebuilt one last year on my 97' GTX.

 

[mikidymac]

The 3 gaskets are because you need to measure the Squish. It's in the manual but basically you need to set the clearance between the top of the piston and the head. Too much and you will have poor performance, too little and you will destroy a piston.

After you do that then leakdown test.

 

[mikidymac]

Sounds like a big vacuum leak if the throttle plates are closed and it's revving to the moon. Couple questions, please forgive me if it's too obvious or insulting.

On the front (mag) and rear (pto) seals are in, new, and undamaged? pto flywheel is installed? mag cover with seal bolted to cases when you installed and were careful not to pinch that seal? Case halves were mated using a good sealant? ie, loctite 518, three bond, etc. Rotary valve cover has an oring? new carb base gaskets? oring on balance shaft case cap? balance shaft fill and drain screws/cap in? pulse line case to carb tight?

Just throwing things out there on a rebuild I know need attention on the 787, I rebuilt one last year on my 97' GTX.

Well said, but please don't use 518/515 on the cases. Please use Three Bond 1211 or 1184.

Here is the Chemical Resistance chart for LocTite 518
Chemical/Solvent Resistance Aged under conditions indicated and tested @ 22 °C % of initial strength

Environment °C 500 h 1000 h 3000 h 5000 h
Motor oil (5W30 -Synthetic) 175 115 110 145
Water/glycol 50/50 80 65 65 55
ATF 150 degrees 60 40 40 40
Unleaded gasoline 15 10 10 5
DEF (AdBlue® ) 95 65 70 85

As you can see it is not gasoline resistant. It is only 15% of it's initial strength at 300 hours with gasoline. Note: your 2-stroke crankcase is always in contact with gasoline.

If you have ever cleaned used Seadoo cases with gasoline it removes all traces of the factory 518.

 

[GGuillot]

Well said, but please don't use 518/515 on the cases. Please use 1211 or 1184.

I don't and that's a preference, I use Three Bond, but some of the most competent builders and experienced, including Fullbore all use loctite 518. That question was asked on the FB forum recently and a bunch of answers were 518.

The service manual specifically calls for loctite 515.

 

[AKnarrowback]

Sorry if I lead you down the wrong road with the carb advice, I must have gotten the wrong idea at where in the process you were. I have to go into my 97 gtx for an oil problem and am watching any 787 conversations for tips.

 

[mikidymac]

I probably shouldn't have said don't use it I guess. I should have said my opinion is to not use it and do your own research
It also depends on who you think are the best engine builders in the industry are. All of the ones I consider to be the best and mentors use 1211 or 1194.

Please look at the Loctite chart that shows it is not gasoline resistant and please try for yourself and see how gasoline quickly removes it then decide for yourself what you want to use.

I do use it on the air box to carbs and the pump just like the factory but I disagree with the factory on using it as a case sealant on my builds. Just my $0.02.

As far as being in the manual even Seadoo stopped using and specing the 518 in 2001 when they switched to 5910 for all 2-stroke cases.

 

[BoaterCycle123]

Very good info! You guys are extremely helpful! I can tell you right now where my problem is. I did not use a sealant between the crank halves! Dang! But yes, all of the other seals are new. I will be pulling the engine and following the service manual a little closer!

So it looks like Three Bond 1211 is the right stuff to use huh?

 

[mikidymac]

I would say 90% or more of PWC engine builders including here use 1211 exclusively.

I prefer 1194 but that's just me as I came from motorcycles before I switched to skis about 25 years ago and so I still like 1194 better for cases as that is what every 2-stroke motorcycle uses.

You will still need 518 for the cylinder o-rings and bolts if you want to follow the manual on that which I do. I also like a little 1211 on the carb base gaskets.

So 1211 if you just want 1 tube for the engine.

 

[AKnarrowback]

We all forget things every once in a while....

 

[jts32]

We all forget things every once in a while....

Lol, glad to see I'm not the only one who has done that.....twice!!

 

[GGuillot]

Very good info! You guys are extremely helpful! I can tell you right now where my problem is. I did not use a sealant between the crank halves! Dang! But yes, all of the other seals are new. I will be pulling the engine and following the service manual a little closer!

So it looks like Three Bond 1211 is the right stuff to use huh?

I use Three Bond 1184, but 1211 is fine, one is thinner or something, or price wise I think 1184 was a little cheaper when I bought it.

 

[GGuillot]

I prefer 1194 but that's just me as I came from motorcycles before I switched to skis about 25 years ago and so I still like 1194 better for cases as that is what every 2-stroke motorcycle uses.

When I bought TB 1184 last year, apparently 1194 was discontinued, I couldn't find it, Amazon has 1211 and 1184 though.

 

[AKnarrowback]

Lol, glad to see I'm not the only one who has done that.....twice!!

I have rebuilt tons of DOO motors over the years, the first one I mess up on is the first time I rebuilt my own........ I just had to laugh.

 

[mikidymac]

When I bought TB 1184 last year, apparently 1194 was discontinued, I couldn't find it, Amazon has 1211 and 1184 though.

The 1184 keeps changing due to environmental regulations, back in the 90's it was 1104 then 1104D then 1194 and now I think you are correct it is 1184 but basically the same stuff. They also make it for a few different labels like Yamabond, Hondabond, Kawachem and MotoSeal are all just repackaged 1184.

 

[BoaterCycle123]

Okay, that issue is not fixed. Resealed motor and waited 24 hours for curing. Still having it. Now reving up to 7k rpm. I am looking to get something to allow for a leak down test. I cannot find anything to plug the intake and exhaust well enough.

Any other thoughts on possible causes?

 

[GGuillot]

Okay, that issue is not fixed. Resealed motor and waited 24 hours for curing. Still having it. Now reving up to 7k rpm. I am looking to get something to allow for a leak down test. I cannot find anything to plug the intake and exhaust well enough.

Any other thoughts on possible causes?

Before you rebuilt the carbs it was revving to 4000 rpms, after you rebuilt the carbs it revs to WOT or 7000 rpms? Has to be something you did in the carbs, it seems if the throttle plates were resting closed (idle screw backed all the way out) it wouldn't rev that high. Pull them off and double check, diaphrams in correctly, needle/seats/springs all the jets in, check valves, everything.

Has to be something you missed...make a check list, verify in service manual, somethings not right.

 

[BoaterCycle123]

So the reason it revved high after rebuild was because it was quite dirty.

But now for the Solve.

We pulled the carbs off another ski, that ran correctly and dropped them in. Same issue. For giggles, I backed the throttle cable adjustment all the way out and poof, worked fine. Easy stupid mistake this whole time.

Check the simple stuff first! I'm a fool...

 

[noviceskier]

So the reason it revved high after rebuild was because it was quite dirty.

But now for the Solve.

We pulled the carbs off another ski, that ran correctly and dropped them in. Same issue. For giggles, I backed the throttle cable adjustment all the way out and poof, worked fine. Easy stupid mistake this whole time.

Check the simple stuff first! I'm a fool...

now that its backed up all the way it revs up/down correctly now? or does it like to hang in the higher rpms after you blip the throttle