RESTO 1996 seadoo gtx 787

[Chrisd1234]

Gentleman my name is chris I’m a new user and I’m hoping I could get some help with an issue I have a 1996 seadoo gtx 787 I replaced my both jugs and pistons followed all specs for replacing and my pto side piston chipped apart into pieces after about 5 minutes running on a hose I rebuilt because I had the same problem at the end of last season and help would be appreciated thank you

 

[AKnarrowback]

Did you just rebuild it? Or did you find out why it failed, correct that problem, then rebuild it?

 

[Chrisd1234]

I just rebuild it I have no idea what could have caused it to happen

 

[AKnarrowback]

What condition was the old piston in when you removed it and did you take the motor down to the crank and inspect things?

 

[Chrisd1234]

The old piston looked the same and Its the same pto side that this is happening to. I did pull it down to the crank and cleaned it out I’m not sure if maybe the race valve is clipping it and breaking a price off and that piece is flying around in there

 

[AKnarrowback]

That is a strange one considering high rpm's and loads were not involved if you only ran it on the hose for a few minutes.

Obviously a mechanical failure somewhere in the system. The amount of deterioration at the edge allowing the ring to be exposed is alarming. I have seen this kind of damage associated with a lean mixture causing the piston to start developing hot spots above the ring, material breaks loose and things just snowball from there. But I don't feel 100% at all that my experience explains your situation since the piston isn't aluminum splattered, dry with damage to the crown as well. It does remind me of having drawn foreign material up from the crank area, but you said you pulled it apart, cleaned and inspected the lower end?

If there was this same kind of damage to the first piston then there has to have been failure of another part of the machine.

Mikidymac, a Moderator on the forum, is one of your best bets for getting you pointed in the right direction. This one has me interested, but I would hate to lead you in the wrong direction.

 

[Chrisd1234]

Thank you so much I appreciate all of your input I’m going to pull the motor apart tommoro and try to get to the bottom of this I will keep you updated

 

[AKnarrowback]

Be observant at every step when you take it apart. You aren't just pulling it down, you are investigating as well.

Good luck.

 

[GGuillot]

Rebuild the carbs, you fixed the result not the cause. I'd go through those carbs thoroughly using genuine oem mikuni kits, new needle/seats and go from there.

I'd also replace the oil injection lines and verify all the injection system is good, after a top end rebuild you should be pre mixing the first tank.

 

[etemplet]

You didn't rebuild the carbs. Its lean.

 

[Chrisd1234]

I did rebuild the carbs and replaced all the oil lines I pulled the jug off today and replaced the piston and checked my rave valve and it looks like the piston or ring may have made contact with it so I shaved it down a hair. I also vacuumed out any debris in between the crank and put everything back together so far so good knock on wood I pulled the head off after 15 20 minutes on the hose all looks well so far

 

[etemplet]

The top of the piston is melting. That's from running lean. Don't run the ski on the hose for more than a couple of minutes. It needs to be in the water. The water seal gets damaged from the heat of running dry.

I'd say you have a lean condition due to the carb. Be it adjustment or something else. The cylinder is not getting enough fuel.