1996 Seadoo GTX 787 losing a cylinder? Cant find pressure leak!

[Travisgg]

I was proud of myself for making these block off plates but they all leak LOL. I used the old gaskets behind them and they are good and snug but they all blow bubbles. It might look like those long bolts aren't holding the plates on tight but there's a nut further down on the thread torquing the plates on. You guys like using tire tubes instead of the old gaskets to make a tight seal?

 

[JC-SUPERJET]

Use Plumbers Test or Expansion Plugs. The big one for the Exhaust can be found online. Google it.

Wipe the Oil off the inner walls of the Manifolds to avoid Plug slippage.

 

[burtshaver2021]

Old inner tube sandwiched between worked for me

 

[Travisgg]

Alright update time...
1) Squish in spec. 1.20+
2) Pressure tested. Slow air leak somewhere.... Real slow but losing a pound every couple minutes. Cant find sprayed the crap out of everything with soapy water including gauge etc. Maybe need to access crank seals and spray?
3) Got anxious and pulled top off. Pics and video below...

 

[Travisgg]

 

[Travisgg]

 

[mikidymac]

View attachment 62617

That is done, time to start over, dang it.

 

[Travisgg]

That is done, time to start over, dang it.

Thoughts on damage there right at the ring end? Interesting know cylinder wear on the carb and exhaust side...

 

[mikidymac]

First off, I don't see any chamfer on the ports. Who did the machine work.
I also don't see any piston wash so is it lean or starving for oil?

 

[Travisgg]

First off, I don't see any chamfer on the ports. Who did the machine work.
I also don't see any piston wash so is it lean or starving for oil?

Frack. I took it to a reputable shop known for accuracy, but I didn't get it checked by my 2-stroke expert after the shop was done with it. They did say it was chamfered... as they go around all the little ports with tool to take the hard edge off. But you're saying it doesn't look like it so maybe it's not a good job?

Yeah not sure about the Piston wash either as it didn't get much run time though.... My two-stroke buddy was saying it look like it was starving for oil as that Teflon coating was all worn down on the Piston side.
Do you have a good picture or link of what a quality chamfer looks like?
So....
1) make sure I get pressure test in spec
2) pull oil pump and test output? Strange though other cylinder is fine?
3)make sure chamfer is done right

 

[JC-SUPERJET]

Chamfering requires the use of a Porting Tool, Dremel Tool or Small Grinder to create a BEVEL all the way around the Ports.

A Deburring Tool does NOT Chamfer the Port edges.

Only have 2 Stroke Cylinders Bore & Hones done by a 2 Stroke Shop.

Any other Shop, either doesn't know or forgets to Chamfer the Ports.

 

[mikidymac]

I don't have a good picture but I honestly don't see any on yours at all.




This would cause it to catch a ring.

Typically when the lean seize or oil seize the damage is on the exhaust port side.

Yours is in a strange location which makes me think the piston to cylinder clearance was not setup correctly by the machine shop.

I have seen a lot of cylinders damaged just like this by really good automotive machine shops that have no clue how to do 2-strokes.

 

[Travisgg]

I don't have a good picture but I honestly don't see any on yours at all.

View attachment 62631
View attachment 62632

This would cause it to catch a ring.

Typically when the lean seize or oil seize the damage is on the exhaust port side.

Yours is in a strange location which makes me think the piston to cylinder clearance was not setup correctly by the machine shop.

I have seen a lot of cylinders damaged just like this by really good automotive machine shops that have no clue how to do 2-strokes.

All right I'll get this pulled apart and over to the two stroke expert for autopsy.

 

[Travisgg]

I also want to see if @mikidymac sqwirms if i oversize 1.00mm on one side only again

 

[Travisgg]

Also just thought of something... Could i be losing pressure to the oil inlet when block of plates are on and I'm pressurizing system for pressure test? Or unlikely.

 

[burtshaver2021]

I also want to see if @mikidymac sqwirms if i oversize 1.00mm on one side only again

He’s already said absolutely not, you could be throwing more money away if you do. I would think being 4 sizes over on one side and factory on the other could put some stress on the crank?

 

[Travisgg]

He’s already said absolutely not, you could be throwing more money away if you do. I would think being 4 sizes over on one side and factory on the other could put some stress on the crank?

Lol. Just trying to stir the pot. I appreciate everyone's help here. Amazing!!

 

[mikidymac]

I also want to see if @mikidymac sqwirms if i oversize 1.00mm on one side only again

Yes, a little

 

[mikidymac]

Also just thought of something... Could i be losing pressure to the oil inlet when block of plates are on and I'm pressurizing system for pressure test? Or unlikely.View attachment 62636

Not likely.
If that is your engine, please replace the small oil lines before they break.

 

[Travisgg]

Hey @mikidymac just side note... Is it possible to get oil starvation on one cylinder and not the other? Only possibility would be plug in that little oil line or bad check valve right? I know my lines look nasty but I think the hoses are actually new I was just trying to crack the paint off them.

 

[mikidymac]

Hey @mikidymac just side note... Is it possible to get oil starvation on one cylinder and not the other? Only possibility would be plug in that little oil line or bad check valve right? I know my lines look nasty but I think the hoses are actually new I was just trying to crack the paint off them.

Yes, that is correct.

 

[JC-SUPERJET]

Next time you break-in a fresh Engine, add Oil to your Fuel Tank (Premix) just in case the Stock Oil Injection isn't working right.

 

[Travisgg]

Is this legit if i want to resleeve?

 

[Travisgg]

Next time you break-in a fresh Engine, add Oil to your Fuel Tank (Premix) just in case the Stock Oil Injection isn't working right.

Smart! Im pretty sure it is working but still smart.

 

[mikidymac]

Is this legit if i want to resleeve?

No, you will still have to have the sleeve machined to final clearance to fit a new piston.
They are not just drop in and go.