[Bob KellyIII]

that should do the trick.. that is a vacuum operated petcock !...
which I think all the ninja's have though some of the very first ones may be manual.... i hope it's a direct replacement for the one you have ! as the compact placement of parts on the Ninja is very close and doesn't allow for much fudging on part's size ! ... the one on my bike does not even have a knob to turn it with you have to take a wide screwdriver or coin to turn it on or off....
these are actually a good thing to have on a carbureted bike because if you lay the bike over and get knocked out the engine will die and because there is no vacuum to activate the gas flow all the gas in your bike won't be gone when you come too....
i think about 5 times in my life I have had a bike fall over at night and nobody heard the thump and you wake up to a bike on it's side and no more gas because you didn't turn off the gas when you left it..... the new vaccum operated petcocks prevent that from happening....
that's kind 'a neet, actually !
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yah a heat gun works or the back of a knife blade will thump those things off usually
in my experience it is usually the Idle jet that gets plugged up first, not always but about 75% / 25% of the time the idle circuit will show that the carb is dirty first.......
it sounds like the screens have been off there a while or damaged, so sense you have the tank off pull the carburetors and do a real thorough job of cleaning the carbs, set aside a entire day to do it, each passage way needs to be cleaned real good .... the idle circuit and the main jet circuit !
don't forget the hole that feeds the emulsifier tube for the main jet as they plug up before the main jet does sometimes ! , same for the idle circuit
...it's obvious to me they made those holes too small but they work good when their clean ! LOL.....
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when I got my Ninja the inside of the tank was rusty... it had several places where rust had taken hold... and even with all the filters in place it still found a way to plug the right cylinder main jet completely solid !
I put KLEEN, a tank treatment that cost about $58 bucks in it. followed the instructions well, and I haven't had a problem with the jets getting plugged again, ...the trick to sloshing that thick white paint around in the gas tank is to tape off the petcock hole and the sending unit hole with 2" wide packing tape... and don't forget the 3 pipes that exit the side of the tank near the front ... I did and got paint all over me !....LOL....
I let the tank dry in the hot sun for 3 days when I was done !
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anybody can do it, just follow instructions.... many older bikes need that
as there is rust all over in their tanks ! and the owner just put in an extra in line fuel filter and never fixed the problem !, just ran it like that !
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Bob.....