2009 KLX 250 will start and idel, but dies if you give it any gas. Any ideas?

You have a blocked carb jet the engine is running very week to prove this give it a little choke and it should then rev up ok
so you need to strip down the carb and clean out all the jets,,use carb cleaner and dont go poking bits of wire into any jets to try to clear them,,,you will only distroy them that way,,,comprest air would help if you have it if not its carb cleaner

Try adjisting the carb. sounds like it may need nothing more than a minor adjustment