92xp 720, bog issue after 5-10 minutes of run time

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psage504

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So I have a 92xp with a 720 from a 96 GTI, computer and harness from same machine.
Starts no problem rips good for the first 10-15 minutes then after that going full throttle it seems to lose power then pick up again. That happened multiple times. Now it seems to run for 2-5 minutes and does the same thing, but this time it died and wouldn't start until it sits for a bit. Thoughts? Had dual carbs and were rebuilt less then 5 hours ago
 
First did you use genuine mikuni parts, new needles and seats and check pop-off and leak down?
Did you replace the fuel selector and strainer?

Try opening the gas cap and see if your have a vacuum on the tank. If the check valve isn't working it can build a negative pressure and starve the carbs.
 
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Yes for the carbs, I didn't replace but I made sure the selector was cleaned out, I blew out the whole unit with the compressor, I will try the gas cap thing next, thanks
 
The selectors almost never take kindly to cleaning since the rubber parts wear out over time and cleaning finishes them off. Given that information I would try bypassing the selector temporarily to see if it is bad, chances are very good it is sucking air.
 
It’s absolutely fuel related. You’re running lean up top, and the motor is beginning to seize causing the shut down... It’s important that you make absolutely sure you used GENUINE Mikuni carb parts and that you go through and take care of any air leaks before you run the ski again....
 
Bypassed the selector didn't help right away, plugs must of been fouled up, changed the plugs and seems to be back to it's old self.
I'll test longer over the weekend and let you guys know.
Thanks again
 
So it runs good after bypassing the fuel selector, issue I'm have now is fouling plugs every couple of hours running the machine hard, is it the cheap Castrol super outboard 2 storke oil I'm using or the carbs too rich?
Thanks again
 
It’s probably a mix of those two things to be honest. Change the oil to something API-TC rated. The Mystik JT-4 Personal Watercraft is a good oil that should be around $25/gal.

For the carb settings, where do you have the low speeds now? I’d try them at 1-1/2 turns out and see how that does...
 
Ok so I'm a retard, there is now o ring on my fuel separator the whole time, would this have caused all my issues?
 
Fuel system can't have any leaks, low pressure testing about 5psi will uncover a problem. Fuel selector valves and water.fuel seperator are common leak points. But if it runs well 1st 10~15 minutes then begins running out of fuel (lean) the air vent for the fuel tank may be acting up. Loosen fuel cap to uncover this possibility.

Running lean can roast pistons, so don't force it in hopes it will resolve itself, find the issue and fix it.
 
So I am still having issues, runs great 5-10, have bypassed fuel separator and selector and is still giving me issues, what should I check next?
 
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