Kawasaki 450r I have a 2007 Kawasaki 450r. It was running fine then After about 30 minutes it would stall no matter how much throttle was given when The clutch was released all the way. It would idle fine,, but progressively got to where it would stall after idling in neutral also. Brought it home and let it cool down. Tried to start it 30 minutes later and now will not even attempt to turn over. I've used the choke and let the engine warm up properly prior to riding. Just went to turn around and it just started stalling all of a sudden when clutch was fully released. Any ideas?

Radiator cooling fans not working? The ECM is protecting the engine by shutting it down.

Sounds like you might have some trash in the fuel system that worked its way into the carburetors. I would suggest having the fuel system serviced.

Could be water in fuel,try some stabile .

you need valve job done and new valves put in and i said new valves do not use old valves again 150.00 per cylinder

contaminated or water in the fuel is most likely the culprit here.
drain the tank and carb (small screw at bottom of carb float bowl)
Add fresh fuel from a CLEAN fuel source. Best to completely drain your fuel can and fill it up with fresh fuel. That way if the fuel can is the culprit you eliminated doing this twice.
What happened was fuel sits on top of water, this is why the bike would still idle. The idle circuit in the carb pulls fuel from a higher point than the main jet. This is also why when you hit the throttle it would just die, it was sucking most like something other than fuel.

Engine stall or RPM fluctuates at idle.

This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve. Buy a can of throttle valve cleaner (do not use carburetor spray cleaner!) from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control

check the side stand switch and clutch switch with a multimeter

I would suspect that the float is sticking. Checking will require removal of (in order): seat, tank, air filter box/backing plate, and finally, the float bowl at the bottom of the carb. Insure that the float is not flooded, and that the float needle is free of trash.

check carb for bent needel or any other damage

The Choke may be stuck or left on.