720 XP Fouling Plugs

[SkiDooStu]

Hi everyone,

I have a 1995 Sea Doo XP that I bought for cheap, assuming there was something wrong with it.

Everytime I take it out, it will run for maybe 5 minutes, then it will foul the spark plugs. If i rub the plugs on a cloth, they are brown with oil. The carb is set to the stock setting for all screws.

I disassembled the engine and hooked up a leak tester to the rotary valve inlet. It seems to hold 8psi of pressure without any problems. I also bench tested the oil pump and it is putting out the correct amount as per the manual. The crankcase was full of oil...

Is there any other way i could be getting oil in my crankcase like this? Perhaps the rotary valve chamber can leak by the inner seals over time? As I said, the inner seals seem to hold a pressure test without any problem.

Thanks for any help!

 

[LegalizeIt]

Sounds like the mixture is too rich...

 

[SkiDooStu]

I tried it with leaner settings and it seemed to do the same thing.

Could the crank case halves themselves be letting in the oil from the rotary valve chamber?

 

[LegalizeIt]

Next thing to check would be the oil pump adjustment. Could be dumping too much oil into the intake manifold...

 

[SkiDooStu]

yes, i volume tested the pump as well as made sure that the marks were lined up...

 

[kustomkarl]

The problem is the rotary valve chamber seals are seeping oil into the cylinders over time. It uses the same oil from the oil injector tank. You could run it for a time without problems, but as time goes on it will seep more and more. I have seen some seadoos run like bug fogers. The only real way to correct it, is rebuild the crank and replace the seals.
Keep spark plugs handy.

Karl

 

[timmyboy76]

one way to find out, is pressure test the rv cavity...10psi for believe 5minutes.

 

[SkiDooStu]

hello, thank you for all of your replies.

I have pressure tested the rv cavity. it holds pressure for 5 minutes and does not drop off. I wonder if it can leak intermittently? The funny thing is, when i first pressure tested it, i swear i could see bubbles at the bottom of the crankcase forming from an air leak, but i can't get it to reproduce the problem.

 

[SkiDooStu]

Sorry to bump this post, but can anyone think of anything else that could let the oil in?? It was definitely oil, and the carb was set to stock so i'm pretty sure it wasn't a carb setting.

The RV cavity held 10psi for 5 minutes without losing any pressure whatsoever.

The oil pump is putting out the exact amount that the manual specifies (we volume tested it with a drill.)

Could the inner seals still be leaking despite them holding the leak down test?

Thank you in advance for any help....

 

[LegalizeIt]

The reason I stopped responding is my limited experience with the oil injection. I was into dirt bikes before my first xp650 back in 93. Oil injection was gone within 3 months. I'm a big believer in pre-mix. You can save a bundle by using Yamalube 2R.

So you don't want to hear my opinion... :rofl:

:cheers:

 

[kustomkarl]

The reason I stopped responding is my limited experience with the oil injection. I was into dirt bikes before my first xp650 back in 93. Oil injection was gone within 3 months. I'm a big believer in pre-mix. You can save a bundle by using Yamalube 2R.

So you don't want to hear my opinion... :rofl:

:cheers:

Even if you go with pre-mix, it won't solve the problem. The engine has a rotary valve/ shaft which needs oil form the injector to keep it lubricated, so even if you go to premix you will still have a weeping problem, because you need to have the shaft chamber full of injector oil from the injector tank. If the test went ok, I'd run it. I have see members run their engines till the thing would't run, due to fouling the spark plugs real bad. It might show signes of lots of smoke when first run after sitting for a while, but that might be it. To correct the problem involves rebuilding the crank seals on each side of the rotary valve chamber, by splitting the cases and pulling the crank. Not a cheap or quick repair.

Karl

 

[LegalizeIt]

:agree:

:cheers:

 

[timmyboy76]

check to make sure, the "throw" on throttle plates are open all the way, at WFO.