Ski runs like crap when the tank is full, but it runs better when empty?

[Roseand]

I played around with that but then still had the issue, and then today I pushed the pickup as far down as it could go..

 

[Roseand]

You're absolutely positive that your check valve is flowing into the tank?

Absolutely positive, since I already tried a new one.

 

[623pwr]

How long was the race gas was sitting in the tank? Maybe you had some contamination or it started to break down? I used to run VP C12 50/50 and if it sat too long it always seemed sluggish. My SXR was pretty thirsty so I would usually try to fry the tank and didn't take too long (35-45 min on a full tank WOT).

Also, I have heard of guys (road racers) saying that Koch stuff retards your timing and to stay away from it.
Not sure if that's what your running though. It sounds like you got it figured out, glad to hear you got rid of that old fuel and it ran better for you.

 

[Roseand]

How long was the race gas was sitting in the tank? Maybe you had some contamination or it started to break down? I used to run VP C12 50/50 and if it sat too long it always seemed sluggish. My SXR was pretty thirsty so I would usually try to fry the tank and didn't take too long (35-45 min on a full tank WOT).

Also, I have heard of guys (road racers) saying that Koch stuff retards your timing and to stay away from it.
Not sure if that's what your running though. It sounds like you got it figured out, glad to hear you got rid of that old fuel and it ran better for you.

Only like a week, and it was regular pump gas, no race gas.

Sooo today I removed the excess hose that came off of my checkvalve and removed that pipe/bulb thingy completely. Also was running like 50/50 racegas/pump just for the heck of it today.. My ski has never ran so freeken good and been so snappy. It was awesome all day, even after some gnarly gnarly inverted stuff. When I was ripping it on just flatwater I was surprised at how snappy it's midrange/bottom end hit was just for a piped 701..
I wonder if it's possible it never was getting enough air into the tank? Some people ditch the check valve and simply coil hose around something, and i had the check valve, then hose wrapped around the fuel pickups, and then that little bulb thingy..Now I'm running a couple of inches of hose and then just the check valve.
Totallllly wierd, but it ran so good today it was amazing.

 

[CARBONX2]

Check that valve is working correctly. If it is, fit it back just with a short piece between valve and tank, and try again. If it struggles again, try leaning out screws to see if there is an improvement.