Sea-Doo SPX 1994 blown top end (PTO side) after changing stator

[mchiappinam]

Hey everyone,

A couple days ago I had a problem with my SPX 1994 (657) for not having spark. After replacing the stator and coil it came back to life yay

I put it in the water today to test in NJ (60 degrees ), it worked great. After running full throttle for about 25 seconds, it died. Started again with no issues and gave full throttle again to confirm if it was running lean. It died in 5 seconds. I started again, running half throttle back to the boat ramp. It was running perfect. So then I gave full throttle again after 1m in half throttle and I was able to run for about 25 seconds again till it died. That gave me a confirmation that I have some issue before the carburetor.

After stopping, I cleaned the gas/water separator filter and replaced my ¼ in line gas filter with a larger one (more flow).

After that, I had a hard time trying to start it, until I gave up and put it back on the trailer. When it was in the trailer I started it very easy, but something wasn't right. Removed the spark plugs and the pto one had some stuff welded to it. That scared me.

I drove home and checked the compression, mag piston 105 psi (usual).
Pto piston 60 psi.

I was sad, of course... Removed the top end and confirmed... It was the piston.

Running lean for a short period of time can cause this? Or probably was another problem?

Bad timing with the stator can be the issue?

Is it possible to replace only the pto piston? (Probably not worth if possible, right?)

Thanks and cheers!!

 

[etemplet]

If you suspect the engine is lean pull the choke. If the engine RPM picks up you're lean, if it bogs or dies you're not lean. Your engine is likely done, crank and all. Two strokes don't like lean.

 

[mchiappinam]

I tried to pull the choke but it died pretty fast. Is it possible to fu#@ the piston with the stator timing off?

 

[mchiappinam]

The center of the cylinder had a hole. Looked like it was sandblasted idk. Will send pics later

 

[mikidymac]

That can only be caused by detonation. Either timing is too advanced or octane is too low. I would say in your case timing.

 

[AKnarrowback]

If you replaced the stator then you needed to do a full retiming of the ignition system. Did you do this? It involves a dial in the spark plug hole to find your BTDC marks, adding your own timing marks and using a timing light to confirm the new components are set right.

A dished in piston crown is just as described, bad timing or bad gas.

On sleds we also see the same condition produced by cold pockets of air or having forgotten to jet back up after riding at high altitude then running at lower elevations.