yz problems !!!

It's not safe to ride until you figure it out. If you run it out of antifreeze you have a chance of destroying the engine. If the weather was really hot and you let the bike idle until it got too hot with no air-flow through the radiators then it is normal for it to overflow coolant. But if the bike isn't really that hot it shouldnt do that. Go check your coolant level, add some if needed, start the bike up and let it run until it gets up to running temp. Keep an eye on it. If it doesn't overflow until it gets really hot, it's working as it should. If it starts overflowing as soon as you start it, you probably have a waterpump issue. If so, you need to take the waterpump cover off and check the impellar. spin the impellar and make sure it's turning freely without slop or alot of resistance or missing fins.

Engine Ice

Sometimes it's just a bad radiator cap.

Check the head gasket, base gasket, and cylinder studs. If compression is getting past the gaskets into the cooling system , it will push water out of the overflow.

Had an older KX125 that broke a cylinder base stud, which allowed compression of the engine to pressurize the cooling system, pumping a steady stream out of the overflow.

Or you could be simply overfilling the radiators. Fill it just up to the bottom of the radiator cap boss, not totally topped off.