Carbs Rebuilt, Runs Great Now Except.....

[SeaDooNewb]

After rebuilding the carbs on my '96 SPX. It idles great in the water and has great throttle response as well as top end. The only problem is that it just cuts out after ~5-10 seconds of running. If I only give it half throttle it will last longer, WOT makes it cut out faster. So you'll be going flat out and it will just cut out like it ran out of gas. It doesn't die, just falls on it's face. After idling for a bit if you give it gas again it will get up out of the water great but fall down soon after.

Seems like the carb bowls are actually running out of fuel so it could be the needle valve springs aren't the right pressure and keeping them closed. I didn't measure the pop off pressure, I just used the same size springs that came in the Mikuni kit that came out of the carbs. Also, it is really hard to start cold, you need to crank if for ~20 seconds before it fires up. Once it does if you shut it off it starts right back up. This makes me think there are small air leaks in the fuel lines and the fuel pump is not able to keep up which would explain both the hard starting and the falling down. I think I'm going to replace all the fuel lines and clamps from the tank to the switch to the carbs.

PS: Since I thought it was a fuel delivery problem I switched it to the reserve tank just for fun. It qut running after a little while so I switched it back to the primary tank and it would not start.

 

[seadoosnipe]

I think you got it!

Seems to me your covering all the bases I'd cover. Like you said, seems that your fuel pump isn't keeping up with the demand of the carbs. Check your vent line too. Make sure all lines are tight, no air leaks and that your return line is clear and your pop off valve is set.
I think you've pretty much got a handle on what your looking for. It's surely a carb fuel pressure or supply problem.