Two Stroke Pressure Testing....can a leak cause a piston to seize? Help!

[n4yhd]

Here is the story. I am new to Waverunners, but have worked on cars for years, so any help is appreciated. I bought a used 95 Waverunner III GP (701 61x). It did not run when I bought it, the owner sprayed fuel into the carburetor to make it fire, but it would not run. I rebuilt the carburetor, and took it out on the water. The rear piston seized. I thought it seized due to the use of the fuel into the carburetor by the prior owner, I thought he did this a lot trying to fix it without success. I honed it out and rebuilt the top end. It ran fine, until about after an hour when it seized up again. Rear piston again, I tore it apart and found the rear piston seized again by the exhaust port. I also found a reed valve stuck open by gummed fuel (rear cylinder). Not wanting to put any more money into it if I could fix it with spare parts, I honed it out again. I know it was over by about .001 and probably out of round, but I tried using the front original piston in the rear hole to see if it would work. The ring end gaps were over by .002. Put it together, it ran. Put it into the water, seized after 20 minutes. Rear piston again. But it started and ran fine at first.

Okay, so the only test I have not done is the pressure testing. Can anyone tell me if there is a leak in the bottom of the engine and it would fail the pressure test could it cause this failure? From what I have read, failing the pressure testing would cause hard starting and generally poor running. Neither of these have been my problems, but I have not done this test and the engine is now apart on my workbench.

I would like to go ahead and bore it out properly and rebuilt the top end, but want to make sure I do not have any other problems so my pistons do not seize again. My thoughts are that the reed valve has been my problem from the beginning, but I did not find it right away. The reed valves have been replaced.

Any ideas, hints, or suggestions are appreciated.

[Technical Support]

Re: Two Stroke Pressure Testing....can a leak cause a piston to seize? Help!

Could be a crank seal or case leak, this will lean out the ski and cause damage, also if the carb still is not supplying enough fuel to the engine it will run lean and cause the piston to seize in the cylinder.