96 GTX 787 Shutting off on idle

[Mohannad57]

I have a 1996 GTX 787, with multiple problems, but This is for an idle issue

when starting up sometimes it takes few tries to start the seadoo so I was told it's the starter assembly need to be changed, which I'm looking for one now, but the problem is when it starts it runs great on high speed yet it keeps shutting off on low rpm or on idle, then I have hard time starting, and most of the time the battery gets drained trying. Any idea what to do to keep it running, or what is wrong with it?

 

[etemplet]

You could have a problem inside the mag cover. If it ever got wet or moisture in the housing the "pick up" for the spark timing can get rust or metal particles on it. Then it can't see the rotor pass thus... it doesn't fire everytime it should. The Pick-Up will test good from the outside but the tip is dirty.

Another problem you could have is a bad rotary valve "worn or bent." That will make the ski difficult to start

Then again, you could have a carb issue.

 

[ace422]

Is this happening on the trailer or in the water? Whats your RPM reading at idle?

 

[artr]

There are number of things that can cause the issues you describe. A little background info would help to diagnose what problems may exist. How long have you had the ski? Does it still have gray fuel lines? When was the last time the carbs were rebuilt using genuine Mikuni parts? What procedure was used to rebuild an set up the carbs? Has your battery been fully charged and load tested?

 

[POPPS]

If you are having difficult cold starts,,,sounds very carb related,,tuff hot starts can sometimes be from excessive rotary valve clearance.,,but you also have tuff cold starts,,,anyway,,,start at the battery,,,losd test,,,check the spark,,,is it a nice bright blue/white?,,,cut the plug wires back 1/4 inch,,to rule that out.,,is it charging?,,check connections in the electrical box.

 

[Mohannad57]

Is this happening on the trailer or in the water? Whats your RPM reading at idle?

On the water mostly when
RMP drops to below 1000

 

[Mohannad57]

You could have a problem inside the mag cover. If it ever got wet or moisture in the housing the "pick up" for the spark timing can get rust or metal particles on it. Then it can't see the rotor pass thus... it doesn't fire everytime it should. The Pick-Up will test good from the outside but the tip is dirty.

Another problem you could have is a bad rotary valve "worn or bent." That will make the ski difficult to start

Then again, you could have a carb issue.

I opened up the rotary valve, it seems ok, yes it has some marks but it's not too bad
Here are some pictures is this really bad and could be the cause of the issue.

 

[Mohannad57]

I have a 1996 GTX 787, with multiple problems, but This is for an idle issue

when starting up sometimes it takes few tries to start the seadoo so I was told it's the starter assembly need to be changed, which I'm looking for one now, but the problem is when it starts it runs great on high speed yet it keeps shutting off on low rpm or on idle, then I have hard time starting, and most of the time the battery gets drained trying. Any idea what to do to keep it running, or what is wrong with it?

Just an update as I opened up some parts and tested them.
i pointed that I was told by a mechanic I need a starter assay and other parts (Rectifier and MPEM) so I started to take apart and test every component, I replaced the Rectifier, but didn't change anything I took out the starter and tested it out of the seadoo it works very well (some of the gears teeth are worn by about 2 mm not much but it works.
however I noticed that the positive connection was not 100% sealed of water that could've got inside the hull as when I shuts off I noticed that it would drain the battery after few tries in the middle of the water.
So my question, while it is running could an electrical short at the starter shuts it off?

 

[artr]

The starter is not connected to 12V unless the starter solenoid is activated by the mpem when you press the start button. If the starter was shorted it probably would not crank and a fuse would blow when you press the start button.

 

[Mohannad57]

Make sense, when I have the difficult hot start, the starter would crank but can't start.


Are you referring to the fuse in the rear box near the solenoid. I never had to replace that.

 

[artr]

I was thinking of that fuse but when I look at the schematic I don't think the starter is directly protected by an external fuse. It may be worth a look in the rear electrical Box that all connections are tight, clean and dry, especially the ground bolt for the coil.
I would try to confirm it is not starting when it shuts off when hot because of no spark. If so, then test under similar conditions where in the chain of components it is losing the spark drive (pick up trigger, cdi, coil, etc.).
I am curious and have a much simpler test to try. When it shuts off when hot before you try to restart, try removing the key from the post for a few seconds, put the key back on and then try to restart. Does that change anything?

 

[etemplet]

I opened up the rotary valve, it seems ok, yes it has some marks but it's not too bad
Here are some pictures is this really bad and could be the cause of the issue.

Valve and all that look just fine.