1994 Sea-Doo GTX Lean Piston Seize

[seadoo@19072]

I have been told that the reason that the engine suddenly shuts off is because it has a “lean piston” seize. There seems to be several reasons that a piston will seize and shut the engine off suddenly: lack of oil, lean fuel mixture adjustment at carburetor, blocked cooling system causing overheat, air leak in engine or fuel system. I have heard that sometime the oil pump on these Sea-Doo’s fail at full throttle and cause the seizure.
I am thinking about premixing a couple of gallons of gas, 40:1 then running at full throttle. I would expect that I am over oiling the system with both oil injection and premix at the slower speeds but if the oil injection pump is failing at full throttle without premix but runs well at full throttle with premixed gas, that would indicate that the oil injection pump is failing. Over the short haul the worst that can happen is heavy exhaust smoke, fouled spark plugs or the engine suddenly shuts off. If it shuts off, it probably is something other than the oil pump. If it continues to run well on the premix, I would either install an oil injection pump block off plate and convert to premixed gas, or remove the pump, test it with an electric drill and/or repair it.
When I remove the spark plugs I can turn the drive shaft very easily with bare hand. I have a flexible inspection camera and do not see any grooves or burns on the cylinder walls or top of the pistons. Since it is now winter and I have the time, would it be a good idea to pull the head off the engine to inspect the pistons and cylinders for any evidence of piston seizure?

 

[Bills86e]

Post the compression on your 657cc engine. Do you do carbs every year, and replace the two oil spigot lines on RV cover?
Is the engine hot or very hot to touch when this occurs.?
Do you have a clear glass fuel filter AFTER the carbs (to see if circulatory system running out of fuel) Keep in mind that fuel also cools the piston.
A leaky exhaust can asphyxiate the engine. Check if jetpump has oil.
If you have a tach, check rpm while running, spray carb cleaner dotting different points of engine, like pulse line - manifold - ft & rr crank bearings.
When you went thru the carbs did you check diaphrams for pin hole?

 

[seadoo@19072]

When I had the dealer tech look at this problem this past summer he checked compression and said it was fine. I do not do the carbs every year. The GTX is a '94 which I purchased new. This is the first time carbs have been serviced. Diaphrams are new. Same problem existed before and after carb rebuild. Never checked the temp of engine. I have only experienced this issue the last 4 or 5 times I test rode the GTX. No glass filter after carbs.

 

[tkarvelis]

Has the fuel lines and fuel selector been replaced? If not, they need to. The old "Grey Tempo" lines break down with ethanol, and create a goo that will clog your carbs, fuel selector etc. Get 25 feet of line, some clamps, new fuel selector, and a genuine Mikuni carb kit. Do not use any other kit on these engines. You will regret it.

 

[mikidymac]

In addition the oil injection system is extremely reliable on these engines and is not a concern.
1. Replace the small 3/32" lines from the oil pump to the intake manifold as they get hard with age and break seizing the engine.
2. Install a new oil injection in-line filter.
3. Only use APT-TC oil NO TCW oil at all.
4. Make sure the oil pump lever is adjusted correctly and moves with the throttle.

If you are getting an actual "lean seize" it is from lack of fuel not oil. If this is actually happening over and over then you are destroying the piston, rings and cylinder and will show as low compression numbers.
If it keeps shutting off at WOT don't keep riding it. You need to find the issue and not keep riding it hoping it will fix itself.