Topic: I'm stumped! carbs gush gas!

[Hush]

Carbs on my son's GSXR250 have me completely buffaloed, floats float and are set correctly, have just today put in new float valves complete with brass tubes, carbs are clean as a whistle.
But when I add gas it gushes out the back of the carbs!!!!!!!
I can't think what I can have missed, the skirts on the CV's are undamaged!
Unfortunately you cannot get a handbook for these bikes as they were not supposed to be sold outside Japan but I was talking to a friend the other day who was in the m/c business for many years and he says they sold them from new but they never could get a service book for them either so used a GSXR400 manual.
What the Hell am I missing guys?

[Hush]

I've been onto the GSXR site and there are hundreds of threads devoted to just this topic, the best I can make out is I'm searching in the wrong area.
I don't know much about vacuum gas taps but I do know when they fail they usually take the rest of the bike with them.
My partner's GSX400 came to us with a sump full of petrol and it was a failure in the carbs that let 12 years old gas seep down past the pistons to fill the sump.
I think this maybe almost my problem here with the GSXR, the vacuum gas tap doesn't seem to be working properly and once gas starts flowing it never stops, in most bikes you would expect the float valves to halt this but maybe on vacuum taps they need the diaphram to hold back the tide.
I would welcome anyone's guesses or superior knowledge as that's all I can come up with right now.

[grcamna2]

Hush,
   I hope you can get the necessary O.E.parts to really freshen up you're petcock so it's as good as new..I've had my issues w/ them..& won 98% of my battles w/ them.The biggest issue w/ them is having the correct O.E. diaphram and having it still pliable and fresh and the sealing area of the casting around that dual diaphram and how it meets up w/ the main body of the petcock;you can bench test it before final installation.The spring pressure should stay original too.
  It'd be good to check you're carb. vent/vacuum lines to be sure they aren't somehow getting fuel introduced into them...which a malfunctioning petcock will do sometimes.

[ThomasD883]

Hey hush, how about some pics of dem internals, sometimes another pair of eyes is all you need.

[Hush]

Yeah them darn carbs gotta come off again so I can try something else so I'll do some photo shoots.
Grcamna2, the whole petrol cock is one piece, no removable parts, I've never seen anything like it so obviously you are supposed to just renew.

[grcamna2]

One solid piece !  Oh Man. I wonder if you could fit one on there from a similar model GSXR...400 or something ? But I imagine it's important to see if it's the same spec...,vacuum draw at a specified rpm...or some stuff. I hope you can find a new one.