Travisgg
Active Member
Oh for sure I just mean can you put the sleeve in that way and then take it to get machined.
1996 Seadoo GTX 787 losing a cylinder? Cant find pressure leak!
- Thread starter Travisgg
- Start date
JC-SUPERJET
Active Member
Needs to align the Sleeve Ports to the Block Ports also...
In the video, the Guy just slides them in but is not even wearing gloves to grab the Sleeve and rotate it for Port alignment.
In the video, the Guy just slides them in but is not even wearing gloves to grab the Sleeve and rotate it for Port alignment.
Travisgg
Active Member
Alright....dropped off cylinder to get checked... Its in spec with what WSM lists. The shops only suggestion was improper warm up potentially, or wasn't cooling properly... So I'm at a loss here still. I guess rebuild and pressure test, measure oil output? and go from there?
TheGTIjetguy
Member
What I am seeing is a hot spot on the piston and cylinder wall. Something is heating up that area enough to gall the aluminum and melt it into your cylinder wall.
I don’t think it’s a water flow cooling issue as the other cylinder, and about 3/4 of this cylinder is fine. There would probably be more uniform damage if overheated.
It looks to me like a tight spot in the cylinder causing friction heating in one spot. I’m shooting in the dark here, but It’s possible your lower cases are deformed and as soon as you bolt your good cylinder down it pulls the cylinder out of round. Is it possible to check the clearances when the jug is torqued in place? Piston removed of course.
Also, I haven’t seen where you replaced the oil pump and check valves. This damage could also be caused by lack of lubrication. Although not a common issue, I would do that or run premix for the next break-in. I personally run 1/75 premix or so all the time in addition to the oil pump. Cheap insurance and unlikely to cause harm.
The fact that this is a reoccurring issue and you’ve already done the obvious stuff would lead me to start looking at other, more strange root causes.
I don’t think it’s a water flow cooling issue as the other cylinder, and about 3/4 of this cylinder is fine. There would probably be more uniform damage if overheated.
It looks to me like a tight spot in the cylinder causing friction heating in one spot. I’m shooting in the dark here, but It’s possible your lower cases are deformed and as soon as you bolt your good cylinder down it pulls the cylinder out of round. Is it possible to check the clearances when the jug is torqued in place? Piston removed of course.
Also, I haven’t seen where you replaced the oil pump and check valves. This damage could also be caused by lack of lubrication. Although not a common issue, I would do that or run premix for the next break-in. I personally run 1/75 premix or so all the time in addition to the oil pump. Cheap insurance and unlikely to cause harm.
The fact that this is a reoccurring issue and you’ve already done the obvious stuff would lead me to start looking at other, more strange root causes.
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Travisgg
Active Member
Thanks man. Just weird the oil would pump fine on the other side right? Going to replace both of the little oil lines to be on the safe side. Yeah and I'll premix first tank as well. Interesting theory on cases being deformed.... I hate that you just suggested that LOL now I'm thinking about it.
Also... I'll have to get a picture but the shop pointed out the base of the cylinder on the back side almost looks like it had a little slant in one spot... So minor but you could kind of see something. Like instead of perfectly straight it almost angled inside lip to outside lip a bit... Weird. That would be more of a pressure test fail spot though I would imagine if it's not sealing. Anyway getting machining done will report back later.
Travisgg
Active Member
Well I finally got the piston in for an autopsy with a two-stroke expert. After he was a finished with his metallurgy analysis lol, he is confident it's an oiling issue in this case. He also agrees that the mikuni oil pumps are bulletproof but there could be a restriction or something causing the oiling issue. So next step is testing flow output to verify. Will report back. Also if anyone found an easy way to maintain 1500 RPMs when bench testing pump let me know. I assume find a drill that has that output....
TheGTIjetguy
Member
Most drills have a two speed gearbox where low speed would be close to 1,500 rpm. If not just run it at 1/3 speed. A common single speed drill runs at 4,000 rpm wide open.
Travisgg
Active Member
Hey @mikidymac . How do you like the look of this chamfer. Better?
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Travisgg
Active Member
Alright motor is back together. Just did pressure test and failed.
Before I took it apart to rebuild top end, it had a slow pressure draw down but couldn't pinpoint it. So now it's all rebuilt and put back together and it has the same pressure loss somewhere. Been soaking this thing in soapy water, even using inspection camera to watch behind the motor can't seem to find any bubbles. Sprayed the pressure tester as well of course....nothing there. Being that the cylinder keeps having issues (4th piston).... Do I need to be looking at a crank seal inspection? So annoyed but maybe that's been the source of the problems?
Before I took it apart to rebuild top end, it had a slow pressure draw down but couldn't pinpoint it. So now it's all rebuilt and put back together and it has the same pressure loss somewhere. Been soaking this thing in soapy water, even using inspection camera to watch behind the motor can't seem to find any bubbles. Sprayed the pressure tester as well of course....nothing there. Being that the cylinder keeps having issues (4th piston).... Do I need to be looking at a crank seal inspection? So annoyed but maybe that's been the source of the problems?
Make sure you check the oil fittings for the rotary cavity to see if the crank seals are leaking into it. I put a bubble of soap over them and see if they blow up from the pressure test.
At this point you are going to have to find that leak and probably should pull the engine to find it.
At this point you are going to have to find that leak and probably should pull the engine to find it.
Air could be leaking into the RV cavity, if you block the nipple for the RV and the vent nipple at the back for the RV and it stops your air leak you will know it’s one of the inner oil seals
Travisgg
Active Member
You said nipple.
Or test the RV by pressurizing in the oil nipple and block vent nipple.
Lol, I’ve been waiting for that
I have a mityvac and it comes with these rubber caps of all different sizes. I used those. I have 2 hose pinchers but I don’t trust them.
General PDP Template
I’ve used these as well with a gear clamp
I’ve used these as well with a gear clamp
What are you testing right now? The RV cavity or are you testing the bottom and top
End through the pulse nipple and now blocking the RV oil lines to see if it will stop
Losing pressure?
End through the pulse nipple and now blocking the RV oil lines to see if it will stop
Losing pressure?
Travisgg
Active Member
No I'll grab some tomorrow to test. I'm pumping through pulse line to pressurize.... Was going to block the rotary oil lines in and out amd then see if pressure keeps dropping?
Personally I would just test the RV cavity. If you block off those RV lines and pressurize through the pulse you will still lose pressure until the rv cavity gets to the same pressure which may take a minute or 2. If you determine from your testing that it’s the inner crank seals leaking then you could instal a shut off valve on the oil line to the RV cavity and turn it off while the machine is not in use. The inner oil seals leaking will not cause the engine to run lean., You could also put ballons over those oil line fittings. If the leak is coming from somewhere else you will need to find it, leaking from outer oil seals or the crankcase mating surface will cause a lean issue.
